Cover Page - shares	9 Months Ended
Cover Page - shares	Sep. 30, 2019	Dec. 13, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-37918
Entity Registrant Name	iRhythm Technologies, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8149544
Entity Address, Address Line One	699 8th Street Suite 600
Entity Address, City or Town	San Francisco,
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94103
City Area Code	415
Local Phone Number	632-5700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		26,624,448
Title of 12(b) Security	Common Stock, Par Value $.0001 Per Share
Trading Symbol	IRTC
Security Exchange Name	NASDAQ
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001388658
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 34,634	$ 20,023
Short-term investments	118,091	58,320
Accounts receivable, net	25,003	19,790
Inventory	3,499	2,062
Prepaid expenses and other current assets	3,653	4,100
Total current assets	184,880	104,295
Long-term investments	9,026	0
Property and equipment, net	17,803	9,158
Operating lease right-of-use assets	91,935
Goodwill	862	862
Other assets	5,574	3,208
Total assets	310,080	117,523
Current liabilities:
Accounts payable	4,187	2,284
Accrued liabilities	32,227	26,688
Deferred revenue	889	1,223
Accrued interest	128	139
Operating lease liabilities, current portion	8,036
Total current liabilities	45,467	30,334
Debt	34,929	34,899
Deferred rent, noncurrent portion		153
Operating lease liabilities, noncurrent portion	87,099
Total liabilities	167,495	65,386
Commitments and contingencies (Note 6)
Stockholders’ equity:
Preferred stock, $0.001 par value – 5,000,000 shares authorized at September 30, 2019 and December 31, 2018; and none issued and outstanding at September 30, 2019 and December 31, 2018	0	0
Common stock, $0.001 par value – 100,000,000 shares authorized at September 30, 2019 and December 31, 2018; 26,525,201 and 24,368,073 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	25	23
Additional paid-in capital	385,614	257,955
Accumulated other comprehensive income (loss)	39	(16)
Accumulated deficit	(243,093)	(205,825)
Total stockholders’ equity	142,585	52,137
Total liabilities and stockholders’ equity	$ 310,080	$ 117,523

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	26,525,201	24,368,073
Common stock, shares outstanding (in shares)	26,525,201	24,368,073

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Revenue, net	$ 54,673	$ 38,441	$ 155,448	$ 105,495
Cost of revenue	13,785	9,953	38,570	27,989
Gross profit	40,888	28,488	116,878	77,506
Operating expenses:
Research and development	13,499	5,086	28,031	13,776
Selling, general and administrative	45,649	32,623	125,876	96,330
Total operating expenses	59,148	37,709	153,907	110,106
Loss from operations	(18,260)	(9,221)	(37,029)	(32,600)
Interest expense	(409)	(861)	(1,258)	(2,580)
Other income, net	396	355	1,066	1,072
Loss before income taxes	(18,273)	(9,727)	(37,221)	(34,108)
Income tax provision	20	0	47	0
Net loss	$ (18,293)	$ (9,727)	$ (37,268)	$ (34,108)
Net loss per common share, basic and diluted (in USD per share)	$ (0.72)	$ (0.40)	$ (1.50)	$ (1.44)
Weighted-average shares, basic and diluted (in shares)	25,247,831	24,059,010	24,818,482	23,764,153

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (18,293)	$ (10,725)	$ (8,250)	$ (9,727)	$ (13,304)	$ (11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Other comprehensive loss:
Net change in unrealized losses on available-for-sale securities	(21)	33	43	19	47	(20)			55	46	49
Comprehensive loss	$ (18,314)	$ (10,692)	$ (8,207)	$ (9,708)	$ (13,257)	$ (11,097)	$ (18,899)	$ (24,354)	$ (37,213)	$ (34,062)	$ (50,329)	$ (29,796)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Cash flows from operating activities
Net loss	$ (37,268)	$ (34,108)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,257	1,673
Stock-based compensation	19,064	11,534
Amortization of debt discount and issuance costs	33	118
Accretion of discounts on investments, net of premium amortization	(616)	(633)
Loss on disposal of assets	0	71
Provision for doubtful accounts and contractual allowances	17,581	9,592
Amortization of operating lease right-of-use assets	7,452
Changes in operating assets and liabilities:
Accounts receivable	(22,795)	(15,078)
Inventory	(1,436)	(637)
Prepaid expenses and other current assets	(12)	(231)
Other assets	(2,366)	319
Accounts payable	(119)	(524)
Accrued liabilities	5,635	3,210
Deferred rent		53
Deferred revenue	(334)	(79)
Operating lease liabilities	(4,079)
Net cash used in operating activities	(17,003)	(24,720)
Cash flows from investing activities
Purchases of property and equipment	(8,640)	(3,687)
Purchases of available-for-sale investments	(146,026)	(74,070)
Maturities of available-for-sale investments	77,900	107,605
Net cash (used in) provided by investing activities	(76,766)	29,848
Cash flows from financing activities
Issuance of common stock in public offering, net	6,409	6,684
Repayment of debt	0	(1,500)
Proceeds from issuance of common stock, net	6,409	6,684
Tax withholding upon vesting of restricted stock awards	(5,111)	(1,638)
Net cash provided by financing activities	108,380	3,546
Net increase in cash and cash equivalents	14,611	8,674
Cash and cash equivalents beginning of period	20,023	8,671
Cash and cash equivalents end of period	34,634	17,345
Supplemental disclosures of cash flow information
Interest paid	1,246	2,552
Non-cash investing and financing activities
Property and equipment costs included in accounts payable and accrued liabilities	2,259	86
Stock offering costs included in accounts payable and accrued liabilities	217	0
Right-of-use assets obtained in exchange for new operating lease liabilities	89,170
Public offering
Cash flows from financing activities
Issuance of common stock in public offering, net	107,082	0
Proceeds from issuance of common stock, net	$ 107,082	$ 0

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Follow-on Common Stock	Common Stock	Common Stock Additional Paid-In Capital	Common Stock Follow-on	Common Stock Follow-on Additional Paid-In Capital
Beginning balance at Dec. 31, 2016				$ (127,061)
Net loss	$ (29,740)			(29,740)
Ending balance (in shares) at Dec. 31, 2017		23,377,315
Ending balance at Dec. 31, 2017	79,341	$ 23	$ 236,184	(156,801)	$ (65)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		214,644
Issuance of common stock in connection with employee equity incentive plans, net			877				$ 877
Tax withholding upon vesting of restricted stock awards	(1,271)		(1,271)	0	0
Stock-based compensation expense	3,247		3,247	0	0
Net loss	(11,077)		0	(11,077)	0
Net change in unrealized gain on investments	(20)		0	0	(20)
Ending balance (in shares) at Mar. 31, 2018		23,591,959
Ending balance at Mar. 31, 2018	72,451	$ 23	239,037	(166,524)	(85)
Beginning balance (in shares) at Dec. 31, 2017		23,377,315
Beginning balance at Dec. 31, 2017	79,341	$ 23	236,184	(156,801)	(65)
Net loss	(24,381)			(24,381)
Ending balance (in shares) at Jun. 30, 2018		23,925,497
Ending balance at Jun. 30, 2018	67,196	$ 23	247,039	(179,828)	(38)
Beginning balance (in shares) at Dec. 31, 2017		23,377,315
Beginning balance at Dec. 31, 2017	79,341	$ 23	236,184	(156,801)	(65)
Net loss	(34,108)
Net change in unrealized gain on investments	46
Ending balance (in shares) at Sep. 30, 2018		24,148,814
Ending balance at Sep. 30, 2018	63,214	$ 23	252,765	(189,555)	(19)
Beginning balance (in shares) at Dec. 31, 2017		23,377,315
Beginning balance at Dec. 31, 2017	$ 79,341	$ 23	236,184	(156,801)	(65)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	798,424
Net loss	$ (50,378)			(50,378)
Net change in unrealized gain on investments	49				49
Ending balance (in shares) at Dec. 31, 2018		24,368,073
Ending balance at Dec. 31, 2018	52,137	$ 23	257,955	(205,825)	(16)
Beginning balance (in shares) at Mar. 31, 2018		23,591,959
Beginning balance at Mar. 31, 2018	72,451	$ 23	239,037	(166,524)	(85)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		333,538
Issuance of common stock in connection with employee equity incentive plans, net			4,193				4,193
Tax withholding upon vesting of restricted stock awards	(267)		267	0	0
Stock-based compensation expense	4,076		4,076	0	0
Net loss	(13,304)		0	(13,304)	0
Net change in unrealized gain on investments	47		0	0	47
Ending balance (in shares) at Jun. 30, 2018		23,925,497
Ending balance at Jun. 30, 2018	67,196	$ 23	247,039	(179,828)	(38)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		223,317
Issuance of common stock in connection with employee equity incentive plans, net			1,614				1,614
Tax withholding upon vesting of restricted stock awards	(99)		99	0	0
Stock-based compensation expense	4,211		4,211	0	0
Net loss	(9,727)		0	(9,727)	0
Net change in unrealized gain on investments	19		0	0	19
Ending balance (in shares) at Sep. 30, 2018		24,148,814
Ending balance at Sep. 30, 2018	63,214	$ 23	252,765	(189,555)	(19)
Beginning balance (in shares) at Dec. 31, 2018		24,368,073
Beginning balance at Dec. 31, 2018	52,137	$ 23	257,955	(205,825)	(16)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		260,570
Issuance of common stock in connection with employee equity incentive plans, net		$ 1					2,121	$ 2,120
Tax withholding upon vesting of restricted stock awards	(3,259)			0	0
Stock-based compensation expense	4,856		4,856	0	0
Net loss	(8,250)		0	(8,250)	0
Net change in unrealized gain on investments	43		0	0	43
Ending balance (in shares) at Mar. 31, 2019		24,628,643
Ending balance at Mar. 31, 2019	47,648	$ 24	261,672	(214,075)	27
Beginning balance (in shares) at Dec. 31, 2018		24,368,073
Beginning balance at Dec. 31, 2018	52,137	$ 23	257,955	(205,825)	(16)
Stock-based compensation expense			11,663
Net loss	(18,975)			(18,975)
Ending balance (in shares) at Jun. 30, 2019		24,836,171
Ending balance at Jun. 30, 2019	46,752	$ 23	271,469	(224,800)	60
Beginning balance (in shares) at Dec. 31, 2018		24,368,073
Beginning balance at Dec. 31, 2018	$ 52,137	$ 23	257,955	(205,825)	(16)
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	426,655
Net loss	$ (37,268)
Net change in unrealized gain on investments	55
Ending balance (in shares) at Sep. 30, 2019		26,525,201
Ending balance at Sep. 30, 2019	142,585	$ 25	385,614	(243,093)	39
Beginning balance (in shares) at Mar. 31, 2019		24,628,643
Beginning balance at Mar. 31, 2019	47,648	$ 24	261,672	(214,075)	27
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		207,528
Issuance of common stock in connection with employee equity incentive plans, net		$ (1)					3,287	3,288
Tax withholding upon vesting of restricted stock awards	(298)			0	0
Stock-based compensation expense	6,807			0	0
Net loss	(10,725)		0	(10,725)	0
Net change in unrealized gain on investments	33		0	0	33
Ending balance (in shares) at Jun. 30, 2019		24,836,171
Ending balance at Jun. 30, 2019	46,752	$ 23	271,469	(224,800)	60
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		110,838
Issuance of common stock in connection with employee equity incentive plans, net							$ 1,001	$ 1,001
Warrants exercised (in shares)		2,850
Issuance of common stock in connection with follow-on public offering, net of discounts and issuance costs						$ 2			$ 107,299	$ 107,297
Issuance of common stock in connection with follow-on public offering, net of discounts and issuance costs (in shares)						1,575,342
Tax withholding upon vesting of restricted stock awards	(1,554)		(1,554)	0	0
Stock-based compensation expense	7,401		7,401	0	0
Net loss	(18,293)		0	(18,293)	0
Net change in unrealized gain on investments	(21)		0	0	(21)
Ending balance (in shares) at Sep. 30, 2019		26,525,201
Ending balance at Sep. 30, 2019	$ 142,585	$ 25	$ 385,614	$ (243,093)	$ 39

Organization and Description of Business	9 Months Ended
Organization and Description of Business	Sep. 30, 2019
Accounting Policies [Abstract]
Organization and Description of Business	Organization and Description of Business iRhythm Technologies, Inc. (the “Company”) was incorporated in the state of Delaware in September 2006. The Company is a digital healthcare company redefining the way cardiac arrhythmias are clinically diagnosed by combining wearable biosensing technology with cloud-based data analytics and deep-learning capabilities. The Company began commercial operations in the United States in 2009 following clearance by the U.S. Food and Drug Administration. The Company is headquartered in San Francisco, California, which also serves as a clinical center. The Company has additional clinical centers in Lincolnshire, Illinois and Houston, Texas and a manufacturing facility in Cypress, California. In March 2016, the Company formed a wholly-owned subsidiary in the United Kingdom. The Company manages its operations as a single operating segment. Substantially all of the Company’s assets are maintained in the United States. The Company derives substantially all of its revenue from sales to customers in the United States. On September 10, 2019, the Company issued and sold an aggregate of 1,575,342 shares (the "Shares") of common stock, in a public offering at a price of $73.00 per share. The Shares included the full exercise of the underwriters’ option to purchase an additional 205,479 shares of common stock. Total proceeds received from the offering were $107.3 million, net of discounts and issuance costs. Revision of Prior Period Financial Statements In preparing the condensed consolidated financial statements as of and for the three and nine months periods ended September 30, 2019, the Company identified errors in its historical accounting for revenues, contractual allowances, allowance for doubtful accounts and certain other items. The identified errors impacted the Company's 2017 annual financial statements, 2018 quarterly and annual financial statements and its 2019 quarterly financial statements. In accordance with SEC Staff Accounting Bulletin No. 99, "Materiality," and SEC Staff Accounting Bulletin No. 108,"Considering the Effects of Prior Year Misstatements when Quantifying Misstatements in Current Year Financial Statements;" the Company evaluated the errors and has determined that the related impacts were not material to any prior annual or interim period, but that correcting the cumulative impact of such errors would be significant to our results of operations for the three and nine months ended September 30, 2019. Accordingly, the Company has determined that it will revise its previously issued financial statements to correct for such errors. In connection with correcting for these newly identified errors, we have also corrected other immaterial errors which were previously accounted for as out-of-period adjustments in the period of identification. A summary of the revisions to certain previously reported financial information is included in Note 13. Revision of Prior Period Financial Statements. The accompanying notes to these consolidated financial statements have also been adjusted to incorporate the revised amounts, where applicable. In addition, in connection with the Company’s Form 10-Q for the three and six months ended June 30, 2019, the Company omitted the rollforward of stockholders’ equity for the three months ended June 30, 2019 and June 30, 2018. The accompanying statements of stockholders’ equity present the rollforward of stockholders’ equity for each of the quarters within the nine months ended September 30, 2019 and 2018 and also incorporates the revised amounts discussed above where applicable. The Company will effect the revision of its annual consolidated financial statements as of and for the year ended December 31, 2018 and for the year ended December 31, 2017 in connection with the prospective issuance of its 2019 Annual Report on Form 10-K and will effect the revision of its unaudited interim financial statements as of and for the three months ended March 31, 2019 and as of and for the three and six-months ended June 30, 2019 in connection with its prospective issuance of its 2020 Form 10-Qs.

Summary of Significant Accounting Policies

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Presentation

The accompanying financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America, or U.S. GAAP, and applicable rules and regulations of the Securities and Exchange Commission, or SEC, regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2018, and related disclosures, have been derived from the audited consolidated financial statements at that date but does not include all

of the information required by GAAP for complete consolidated financial statements. These unaudited condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments (consisting only of normal recurring adjustments) that are necessary for the fair statement of the Company’s condensed consolidated financial information. Certain prior period amounts in the accompanying consolidated financial statements have been reclassified to conform to current period presentation. The results of operations for the nine months ended September 30, 2019 are not necessarily indicative of the results to be expected for the year ending December 31, 2019, or for any other interim period or for any other future year.

The accompanying interim unaudited condensed consolidated financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto for the year ended December 31, 2018, included in the Company’s annual report on Form 10-K, filed with the SEC on March 4, 2019.

Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowance

Accounts receivable includes amounts due to the Company from healthcare institutions, third-party payors, and government payors and their related patients, as a result of the Company's normal business activities. Accounts receivable is reported on the condensed consolidated balance sheets net of an estimated allowance for doubtful accounts and a contractual allowance.

The Company establishes an allowance for doubtful accounts for estimated uncollectible receivables based on its historical experience and recognizes the provision as a component of selling, general and administrative expenses. The Company records a provision for contractual allowances based on the estimated differences between contracted amounts and expected collection rates. Such provisions are based on the Company's historical experience and are reported as a reduction of revenue.

The following table presents the changes in the allowance for doubtful accounts (in thousands):



	Nine Months Ended September 30, 2019			Year Ended December 31, 2018
Balance, beginning of period	$	7,296		$	4,486
Add: provision for doubtful accounts	6,473			7,353
Less: write-offs, net of recoveries and other adjustments	(6,439		)	(4,543		)
Balance, end of period	$	7,330		$	7,296

The following table presents the changes in the contractual allowance (in thousands):



	Nine Months Ended September 30, 2019			Year Ended December 31, 2018
Balance, beginning of period	$	9,205		$	6,345
Add: provision for contractual allowances	11,108			9,095
Less: realized contractual adjustments	(7,162		)	(6,235		)
Balance, end of period	$	13,151		$	9,205

Concentrations of Risk

Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of cash and cash equivalents, investments and accounts receivable. Cash balances are deposited in financial institutions which, at times may be in excess of federally insured limits. Cash equivalents are invested in highly rated money market funds. The Company invests in a variety of financial instruments, such as, but not limited to, United States Government securities, corporate notes, commercial paper and, by policy, limits the amount of credit exposure with any one financial institution or commercial issuer. The Company has not experienced any material losses on its deposits of cash and cash equivalents or investments.

Concentrations of credit risk with respect to accounts receivable are limited due to the large number of customers comprising the Company’s customer base. The Company does not require collateral. The Company records an allowance for

doubtful accounts when it becomes probable that a receivable will not be collected. Federal government agencies, including Centers for Medicare and Medicaid Services (“CMS”) and the military, accounted for approximately 36% and 33% of the Company’s revenue for the three and nine months ended September 30, 2019, respectively and 38% and 37%, of the Company’s revenue for the three and nine months ended September 30, 2018. Accounts receivable related to federal government agencies accounted for 21% and 17% at September 30, 2019 and December 31, 2018, respectively.

Revenue Recognition

The Company’s revenue is generated primarily from the provision of its cardiac rhythm monitoring service, the Zio XT service. The Zio XT is a cardiac rhythm monitoring service that has a patient wear period of up to 14 days and is billable when the monitoring reports are delivered to the healthcare provider, which is also when the service is complete and the Company recognizes revenue. The time from when the patient has the Zio XT device applied to the time the report is posted is generally around 20 days. The Company concludes that the Zio XT service is one performance obligation on the basis that the customer cannot benefit from each component of the service on its own or together with other resources that are readily available to the customer

The Company recognizes as revenue the amount of consideration to which it expects to be entitled in exchange for performing the service. The consideration the Company is entitled to varies by portfolio, as further defined below, and includes estimates that require significant judgment by management. A unique aspect of healthcare is the involvement of multiple parties to the service transaction. In addition to the patient, often a third-party, for example a commercial or governmental payor or healthcare institution, will pay the Company for some or all of the service on the patient’s behalf. Separate contractual arrangements exist between the Company and third-party payors that establish amounts the third-party payor will pay on behalf of a patient for covered services rendered.

A small part of the Company’s transactions are covered by third-party payors with whom there is no contractual agreement or not an established amount the third-party payor will pay. In determining the collectibility and transaction price for its service, the Company considers factors such as insurance claims which are adjudicated as allowable under the applicable policy and payment history from both payors and patient out-of-pocket costs, payor coverage, whether there is a contract between the payor or healthcare institution and the Company, historical amount received for the service, and any current developments or changes that could impact reimbursement and healthcare institution payments. Certain of these factors are forms of variable consideration which are only included in the transaction price to the extent it is probable that a significant reversal of cumulative revenue will not occur when the uncertainty associated with the variable consideration is subsequently resolved.

A summary of the payment arrangements with third-party payors and healthcare institutions is as follows:


•	Contracted third-party payors – The Company has contracts with negotiated prices for services provided for patients with commercial healthcare insurance carriers.


•	CMS – The Company has received independent diagnostic testing facility approval from regional Medicare Administrative Contractors and will receive reimbursement per the relevant Current Procedural Terminology (“CPT”) code rate for the services rendered to the patient covered by CMS.


•	Non-contracted third-party payors: Non-contracted commercial and government payors often reimburse out-of-network rates provided under the relevant CPT codes on a case-by-case basis. The transaction price is based on factors including an average of the Company’s historical collection experience for non-contracted services. This rate is reviewed at least quarterly.


•	Healthcare institutions – Healthcare institutions are typically hospitals or physician practices in which the Company has negotiated amounts for its monitoring services, including certain governmental agencies such as the Veteran’s Administration and Department of Defense.

The Company is utilizing the portfolio approach practical expedient under ASC 606 for revenue recognition whereby services provided under each of the above payor types form a separate portfolio. The Company accounts for the contracts within each portfolio as a collective group, rather than individual contracts. Based on history with these portfolios and the similar nature and characteristics of the patients within each portfolio, the Company has concluded that the financial statement effects are not materially different than if accounting for revenue on a contract-by-contract basis.

For contracted and CMS portfolios, the transaction price is determined based on negotiated rates, and the Company has historical experience collecting substantially all of these contracted rates. These contracts also impose a number of obligations regarding billing and other matters, and our noncompliance with a material term of such contracts may result in a denial of the

claim. The Company accounts for denied claims as a form of variable consideration that is included as a reduction to the transaction price recognized as revenue. The Company estimates the denied claims based on historical information. The Company monitors the estimated denied claims against the latest available information, and subsequent changes to the estimated denied claims are recorded as an adjustment to revenue in the periods during which such changes occur. Historical cash collection indicates that it is probable that substantially all of the transaction price, less the estimate of denied claims, will be received. Contracted payors may require that we bill patient co-payments and deductibles and from time to time we may not be able to collect such amounts due to credit risk. The Company provides for estimates of uncollectible patient accounts receivable, based upon historical experience, at the time revenue is recognized, with such provisions presented as bad debt expense within the selling, general and administrative line item of the condensed consolidated statement of operations. Adjustments to these estimates for actual experience are also recorded as an adjustment to bad debt expense.

For non-contracted portfolios, the Company is providing an implicit price concession due to the lack of a contracted rate with the underlying payor, the result of which requires the Company to estimate the transaction price based on historical cash collections utilizing the expected value method. All subsequent adjustments to the transaction price are recorded as an adjustment to revenue.

For healthcare institutions, the transaction price is determined based on negotiated rates, and the Company has historical experience collecting substantially all of these contracted rates. Historical cash collection indicates that it is probable that substantially all of the transaction price will be received. As such, the Company is not providing an implicit price concession but, rather, has chosen to accept the risk of default, and any subsequent uncollected amounts are recorded as bad debt expense.

Disaggregation of Revenue

The Company disaggregates revenue from contracts with customers by payor type. The Company believes these categories aggregate the payor types by nature, amount, timing and uncertainty of its revenue streams. Disaggregated revenue by payor type and major service line for three and nine months ended September 30, 2019 and September 30, 2018 were as follows (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Contracted third-party payors	$	25,961	$	14,887	$	72,040	$	38,270
Non-contracted third-party payors	2,686		3,126		9,016		10,302
Centers for Medicare & Medicaid	15,379		10,952		42,573		29,317
Healthcare Institutions	10,647		9,476		31,819		27,606
Total	$	54,673	$	38,441	$	155,448	$	105,495

Contract Liabilities

ASC 606 requires an entity to present a revenue contract as a contract liability when the Company has an obligation to transfer goods or services to a customer for which the Company has received consideration from the customer, or an amount of consideration from the customer is due and unconditional (whichever is earlier).

Certain of the Company’s customers pay the Company directly for the Zio XT service upon shipment of devices. Such advance payments are contract liabilities and are recorded as deferred revenue on the Condensed Consolidated Balance Sheets and revenue is recognized when reports are delivered to the healthcare provider. The total revenue recognized during the nine months ended September 30, 2019 and September 30, 2018 that was included in the contract liability balance at the beginning of 2019 and 2018, respectively, was $1.2 million.

Contract Costs

Under ASC 340, the incremental costs of obtaining a contract with a customer are recognized as an asset. Incremental costs of obtaining a contract are those costs that an entity incurs to obtain a contract with a customer that it would not have incurred if the contract had not been obtained.

The Company’s current commission programs are considered incremental. However, as a practical expedient, ASC 340 permits the Company to immediately expense contract acquisition costs, as the asset that would have resulted from capitalizing these costs will be amortized in one year or less.

Leases

Identifying a lease

The Company determines whether a contract contains a lease at the inception of a contract. If the contract conveys the right to control the use of an identified asset for a period of time in exchange for consideration, the Company considers the contract to contain a lease. The Company determines whether a contract conveys the right to control the use of an identified asset for a period of time if the contract contains both of the following terms:


•	The right to obtain substantially all of the economic benefits from use of the identified asset; and


•	The right to direct the use of the identified asset.

Discount rate for leases

On January 1, 2019, the rate implicit in the Company’s leases was not readily determinable. As such, the Company used its incremental borrowing rate to calculate its right-of-use assets and lease liabilities upon the adoption of ASC 842. The Company determined the appropriate incremental borrowing rate by utilizing the interest rate obtained in connection with the Third Amended and Restated Loan and Security Agreement with Silicon Valley Bank (“Third Amended and Restated SVB Loan Agreement”) which was finalized on October 23, 2018.

On October 4, 2018, the Company entered into an office lease (“San Francisco Lease”) to rent approximately 117,560 rentable square feet in San Francisco, California, which became the Company’s new headquarters in October 2019. The San Francisco Lease commenced on May 13, 2019 and the Company determined that the interest rate associated with the Third Amended and Restated SVB Loan Agreement could not be utilized as the incremental borrowing rate associated with the San Francisco Lease due to the term of the lease, as well as annual rental payments. The Company determined the appropriate incremental borrowing rate by using a synthetic credit rating which was estimated based on an analysis of outstanding debt of companies with similar credit and financial profiles.

Lease term

The lease term is generally the minimum noncancelable period of each lease. The Company does not include option periods in determining the right-of-use asset and operating lease liability at inception unless it is reasonably certain that the Company will exercise the option at inception or when a triggering event occurs. As of September 30, 2019, no renewal options were included in the determination of lease terms.

Lease Modification

The San Francisco Lease is in the same building with the same landlord as the lease for the Company’s prior headquarters in San Francisco (“existing lease”). Upon the commencement of the San Francisco Lease, the existing lease which had an original expiration date of February 2020, was modified to expire in September 2019.

Recently Adopted Accounting Guidance

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-2, Leases (“Topic 842”), which requires lessees to recognize lease liabilities and corresponding right-of-use assets on the consolidated balance sheet for all leases. For finance leases, the lessee would recognize interest expense and amortization of the right-of-use asset and, for operating leases, the lessee would recognize a straight-line lease expense. As of September 30, 2019, the Company does not have any finance leases. Topic 842 also changes the definition of a lease and expands the disclosure requirements of lease arrangements. The Company has no embedded leases with suppliers. Upon adoption of Topic 842 on January 1, 2019 using the modified retrospective method, the Company recognized right-of-use assets of $10.2 million and lease liabilities of $10.0 million. There was no cumulative-effect adjustment recorded on January 1, 2019. The Company adopted the following practical expedients allowed under Topic 842:


•	The package of three practical expedients, which allows entities to make an election that allows them not to reassess (1) whether existing or expired contracts contain embedded leases under Topic 842, (2) lease classification of existing or expiring leases, and (3) indirect costs for existing or expired leases;


•	Combining lease and non-lease components practical expedient, which allows lessees, as an accounting policy election by class of underlying asset, to choose not to separate non-lease components from lease components and instead to account for each separate lease component and the non-lease components associated with that lease component as a single lease component; and


•	Comparative reporting practical expedient, which allows entities to initially apply Topic 842 at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption.

For further details, refer to Note 6. Commitments and Contingencies.

Recent Accounting Standards or Updates Not Yet Effective

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments, which requires the measurement and recognition of expected credit losses for financial assets held at amortized cost, including trade receivables. ASU No. 2016-13 replaces the existing incurred loss impairment model with an expected loss model that requires the use of forward-looking information to calculate credit loss estimates. It also eliminates the concept of other-than-temporary impairment and requires credit losses related to available-for-sale debt securities to be recorded through an allowance for credit losses rather than as a reduction in the amortized cost basis of the securities. The Company will adopt this standard in the first quarter of fiscal 2020 and is evaluating the impact of adopting this amendment to its consolidated financial statements.

In August 2018, the FASB issued ASU No. 2018-15, Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement that is a Service Contract, which amended its guidance for costs of implementing a cloud computing service arrangement to align the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. This new standard also requires customers to expense the capitalized implementation costs of a hosting arrangement that is a service contract over the term of the hosting arrangement. This new standard becomes effective for the Company in the first quarter of fiscal year 2020, with early adoption permitted. This new standard can be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. The Company is evaluating the impact of adopting this amendment to its consolidated financial statements.

Cash Equivalents and Investments

9 Months Ended

Sep. 30, 2019

Cash Equivalents And Investments [Abstract]

Cash Equivalents and Investments

The fair value of cash equivalents and available-for-sale investments at September 30, 2019 and December 31, 2018, were as follows (in thousands):



	September 30, 2019
	Amortized Cost		Gross Unrealized					Estimated Fair Value
	Amortized Cost		Gains		Losses			Estimated Fair Value
Money market funds	$	24,034	$	—	$	—		$	24,034
U.S. government securities	85,435		34		—			85,469
Corporate notes	15,017		6		(1		)	15,022
Commercial paper	34,592		—		—			34,592
Total cash equivalents and available-for-sale investments	$	159,078	$	40	$	(1	)	$	159,117
Classified as:
Cash equivalents								$	32,000
Short-term investments								118,091
Long-term investments								9,026
Total cash equivalents and available-for-sale investments								$	159,117
	December 31, 2018
	Amortized Cost		Gross Unrealized					Estimated Fair Value
	Amortized Cost		Gains		Losses			Estimated Fair Value
Money market funds	$	10,606	$	—	$	—		$	10,606
U.S. government securities	9,976		—		(1		)	9,975
Corporate notes	16,514		3		(18		)	16,499
Commercial paper	36,331		—		—			36,331
Total cash equivalents and available-for-sale investments	$	73,427	$	3	$	(19	)	$	73,411
Classified as:
Cash equivalents								$	15,091
Short-term investments								58,320
Total cash equivalents and available-for-sale investments								$	73,411

The following table summarizes the fair value of the Company’s cash equivalents, short-term and long-term marketable securities classified by maturity (in thousands):



	September 30, 2019		December 31, 2018
Due within one year	$	150,091	$	73,411
Due after one year through three years	9,026		—
Total cash equivalents and available-for-sale investments	$	159,117	$	73,411

The following tables present the Company's available-for-sale securities that were in an unrealized position as of December 31, 2018 (in thousands):



	December 31, 2018
	Less than 12 months					12 Months or Greater					Total
Assets	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government securities	$	5,977	$	(1	)	$	—	$	—		$	5,977	$	(1	)
Corporate notes	11,521		(10		)	2,993		(8		)	14,514		(18		)
Total	$	17,498	$	(11	)	$	2,993	$	(8	)	$	20,491	$	(19	)

Unrealized losses as of September 30, 2019 were not material. Available-for-sale securities held as of September 30, 2019 had a weighted average maturity of 161 days. At September 30, 2019, one investment was in an unrealized loss position and no investments have been in an unrealized loss position for more than one year.

Fair Value Measurements

9 Months Ended

Sep. 30, 2019

Fair Value Disclosures [Abstract]

Fair Value Measurements

The Company discloses and recognizes the fair value of its assets and liabilities using a hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The hierarchy gives the highest priority to valuations based upon unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to valuations based upon unobservable inputs that are significant to the valuation (Level 3 measurements). The guidance establishes three levels of the fair value hierarchy as follows:

Level 1 - Inputs are unadjusted quoted prices in active markets for identical assets or liabilities at the measurement date.

Level 2 - Inputs (other than quoted market prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life.

Level 3 - Inputs reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model.

Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and consider factors specific to the asset or liability. The corporate notes, commercial paper and government securities are classified as Level 2 as they were valued based upon quoted market prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active and model-based valuation techniques for which all significant inputs are observable in the market or can be corroborated by observable market data for substantially the full term of the assets.

The fair value of the Company’s outstanding interest-bearing obligations is estimated using the net present value of the future payments, discounted at an interest rate that is consistent with market interest rates, which is a Level 2 input. The carrying amount and the estimated fair value of the Company’s outstanding interest-bearing obligations at September 30, 2019 are $34.9 million and $35.2 million, respectively. The carrying amount and the estimated fair value of the Company’s outstanding interest-bearing obligations at December 31, 2018 were $34.9 million and $34.9 million, respectively.

The Company had no transfers between levels of the fair value hierarchy of its assets measured at fair value.

The following tables present the fair value of the Company’s financial assets determined using the inputs defined above (in thousands).



	September 30, 2019
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	24,034	$	—	$	—	$	24,034
U.S. government securities	—		85,469		—		85,469
Corporate notes	—		15,022		—		15,022
Commercial paper	—		34,592		—		34,592
Total	$	24,034	$	135,083	$	—	$	159,117



	December 31, 2018
	Level 1		Level 2		Level 3		Total
Assets
Money market funds	$	10,606	$	—	$	—	$	10,606
U.S. government securities	—		9,975		—		9,975
Corporate notes	—		16,499		—		16,499
Commercial paper	—		36,331		—		36,331
Total	$	10,606	$	62,805	$	—	$	73,411

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Commitments and Contingencies

9 Months Ended

Sep. 30, 2019

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Lease Arrangements

The Company leases office, manufacturing, and clinical centers under non-cancelable operating leases which expire on various dates through 2031. These leases generally contain scheduled rent increases or escalation clauses and renewal options. Operating lease right-of-use assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. The operating lease right-of-use assets also include any lease payments made to the lessor at or before the commencement date as well as variable lease payments which are based on a consumer price index. The Company is also subject to variable lease payments related to janitorial services and electricity which are not included in the operating lease right-of-use asset as they are based on actual usage. The Company recognizes operating lease expense on a straight-line basis over the lease period. The total operating lease cost recognized during the nine months ended September 30, 2019 was $8.1 million and cash paid for operating leases during the nine months ended September 30, 2019 was $4.9 million.

The term of the San Francisco lease began on May 13, 2019, and expires on August 31, 2031. The Company is entitled to one option to extend the San Francisco Lease for a five-year term, subject to certain requirements. In addition, the landlord will provide a tenant improvement allowance of up to $2.4 million for leasehold improvements in connection with the cost of construction of the initial alterations within the premises.

The Company has obtained a standby letter of credit in the amount of $6.9 million, which may be drawn down by the landlord to be applied for certain purposes upon the Company’s breach of any provisions under the San Francisco Lease.

As of September 30, 2019, maturities of operating lease liabilities were as follows (in thousands):



Period Ending December 31:
2019 (remainder of year)	$	1,558
2020	11,766
2021	11,680
2022	11,357
2023	11,696
Thereafter	98,818
	146,875
Less: imputed interest	(51,740		)
Total lease liabilities	$	95,135

Minimum future lease payments previously disclosed in the 2018 10-K and under the previous lease accounting standard, which includes annual rental payments for the San Francisco Lease which commenced May 13, 2019, for the year ended December 31, 2018 are as follows (in thousands):



Period Ending December 31:
2019	$	8,135
2020	10,669
2021	10,828
2022	11,150
2023	11,483
Thereafter	98,209
Total	$	150,474

The weighted average remaining lease term of the Company’s operating leases as of September 30, 2019 was 11.8 years. The weighted average discount rate of the Company’s operating leases was 7.35% as of September 30, 2019.

Legal Proceedings

From time to time, the Company may become involved in legal proceedings arising from the ordinary course of its business. Management is currently not aware of any matters that could have a material adverse effect on the financial position, results of operations or cash flows of the Company.

Collaboration Agreement

On September 3, 2019, the Company entered into a Development Collaboration Agreement (the “Agreement”) with Verily Life Sciences LLC ("Verily"). The Agreement, which is over a 24 month term, involves joint development and production of intellectual property between the Company and Verily. Each participant has primary responsibility for certain aspects of development and approval, with all processes to be performed at each respective party’s own cost. Costs incurred by the Company in connection with the Agreement will be expensed as research and development expense in accordance with ASC 730, Research and Development.

The Company and Verily will develop certain next-generation atrial fibrillation (“AF”) screening, detection, or monitoring products pursuant to the Collaboration Agreement, which products will involve combining Verily’s technology with the Company’s technology to create an end to end system. Under the terms of the Collaboration Agreement, the Company paid Verily an upfront fee of $5.0 million in cash, which is included in accrued liabilities as of September 30, 2019. In addition, the Company has agreed to make additional payments to Verily up to an aggregate of $12.75 million in milestone payments upon achievement of various development and regulatory milestones over the 24 months of the Collaboration Agreement, which payments will be made in cash to Verily.

The Collaboration Agreement provides each party with licenses to use certain intellectual property of the other party for development activities in the field of AF screening, detection, or monitoring. Ownership of developed intellectual property will be allocated to the Company or Verily depending on the subject matter of the underlying developed intellectual property, and, for certain subject matter, shall be jointly owned.

During the three months ended September 30, 2019, the Company recognized $5.0 million of research and development expense related to the Agreement.

Indemnifications

In the ordinary course of business, the Company enters into agreements pursuant to which it agrees to indemnify customers, vendors, lessors, business partners, and other parties with respect to certain matters, including losses arising out of the breach of such agreements, services to be provided by us, or from intellectual property infringement claims made by third parties. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has also entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities

that may arise by reason of their status or service as directors or officers to the fullest extent permitted by applicable law. The Company currently has directors’ and officers’ insurance. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions, and believes that the estimated fair value of these indemnification obligations is not material and it has not accrued any amounts for these obligations.

Debt	9 Months Ended
Debt	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	Debt Pharmakon Loan Agreement In December 2015, the Company entered into a Loan Agreement with Biopharma Secured Investments III Holdings Cayman LP (the “Pharmakon Loan Agreement”). The Pharmakon Loan Agreement provides for up to $55.0 million in term loans split into two tranches as follows: (i) the Tranche A Loans are $30.0 million in term loans, and (ii) the Tranche B Loans are up to $25.0 million in term loans. The Tranche A Loans were drawn on December 4, 2015. The Tranche B Loans were available to be drawn prior to December 4, 2016. No additional draw was taken. The Tranche A Loans bear interest at a fixed rate equal to 9.50% per annum that is due and payable quarterly in arrears. During the first eight calendar quarters, 50% of the interest due and payable was added to the then outstanding principal. In December 2015, the Company used the proceeds from the Pharmakon Loan Agreement to repay $4.9 million of bank debt to Silicon Valley Bank (“SVB”). The issuance costs and debt discount have been netted against the borrowed funds on the balance sheet. On October 23, 2018, the Company repaid the principal amount of the Tranche A Loan of $30.0 million and related accrued interest of $3.3 million. The Company incurred a $3.0 million loss in connection with the early extinguishment of the Pharmakon Loan Agreement which included a prepayment premium fee of $1.0 million and additional consideration related to the prepayment of $1.5 million. Bank Debt In December 2015, the Company entered into a Second Amended and Restated Loan and Security Agreement with SVB, (the “SVB Loan Agreement”). Under the SVB Loan Agreement, the Company may borrow, repay and reborrow under a revolving credit line, but not in excess of the maximum loan amount of $15.0 million, until December 4, 2018, when all outstanding principal and accrued interest becomes due and payable. Any principal amount outstanding under the SVB Loan Agreement shall bear interest at a floating rate per annum equal to the rate published by The Wall Street Journal as the “Prime Rate” plus 0.25%. The Company may borrow up to 80% of its eligible accounts receivable, up to the maximum of $15.0 million. In August 2016, the Company obtained a $3.1 million standby letter of credit pursuant to the SVB Loan Agreement in connection with a lease for its San Francisco office. In October 2018, the Company entered into the Third Amended and Restated Loan and Security Agreement with SVB (“Third Amended and Restated SVB Loan Agreement”). This Agreement amends and restates the Second Amended and Restated Loan and Security Agreement between the Company and SVB dated December 4, 2015, as amended by the First Loan Modification Agreement between the Company and SVB dated August 22, 2016. Pursuant to the Third Amended and Restated SVB Loan Agreement, the Company obtained a term loan (“SVB Term Loan”) for $35.0 million. Total proceeds from the SVB Term Loan were used to pay off the loan agreement with Biopharma Secured Investments III Holdings Cayman LP (“Pharmakon”), totaling $35.8 million. The Company will make interest-only payments through October 31, 2020, followed by 36 monthly payments of principal plus interest on the SVB Term Loan. Interest charged on the SVB Term Loan will be the greater of (a) a floating rate based on the “Prime Rate” published by The Wall Street Journal minus 0.75%, or (b) 4.25%. Under the Third Amended and Restated SVB Loan Agreement, the Company may borrow, repay, and reborrow under a revolving credit line, but not in excess of the maximum loan amount of $25.0 million, which includes an $11.0 million standby letter of credit sublimit availability. In October 2018, a $6.9 million standby letter of credit was obtained in connection with a lease for the Company’s San Francisco headquarters. Any principal amount outstanding under the Third Amended and Restated SVB Loan Agreement revolving credit line shall bear interest at an amount that is the greater of (a) a floating rate per annum equal to the rate published by The Wall Street Journal as the “Prime Rate” or (b) 5.00%. The Company may borrow up to 75% of eligible accounts receivable, up to the maximum of $25.0 million. As of September 30, 2019, no amount was outstanding under the revolving credit line. The Third Amended and Restated Loan Agreement requires the Company to maintain a minimum consolidated liquidity ratio or minimum adjusted Earnings Before Interest, Tax, Depreciation, and Amortization during the term of the loan facility. In addition, the SVB Loan Agreement contains customary affirmative and negative covenants and events of default. The Company was in compliance with loan covenants as of September 30, 2019. The obligations under the Third Amended and Restated Loan Agreement are collateralized by substantially all assets of the Company. California HealthCare Foundation Note In November 2012, the Company entered into a Note Purchase Agreement and Promissory Note with the California HealthCare Foundation (the “CHCF Note”), through which the Company borrowed $1.5 million. The CHCF Note accrued simple interest of 2.0%. The accrued interest and the principal was to mature in November 2016. In partial consideration for the issuance of the CHCF Note, the Company issued warrants to purchase 22,807 shares of the Company’s Series D convertible preferred stock. In June 2015, the Company amended the CHCF Note to extend the maturity date to May 2018. The CHCF Note was subordinate to other debt. In May 2018, the Company repaid the principal amount of $1.5 million and related $0.2 million in accrued interest on the CHCF Note.

Equity Incentive Plans

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Equity Incentive Plans

Incentive Plans

Equity Incentive Plan Activity

A summary of share-based awards available for grant under the 2016 Equity Incentive Plan is as follows:



	Awards Available for Grant
Balance at December 31, 2017	4,034,152
Additional awards authorized	1,168,865
Awards granted	(666,913	)
Awards forfeited	124,478
Awards withheld for tax purposes	56,710
Balance at December 31, 2018	4,717,292
Additional awards authorized	1,218,402
Awards granted	(620,624	)
Awards forfeited	155,253
Awards withheld for tax purposes	58,341
Balance at September 30, 2019	5,528,664

During the nine months ended September 30, 2019, 600,614 restricted stock units ("RSUs") were granted, 115,260 RSUs vested, and 151,729 RSUs were forfeited.

The following table summarizes stock option activity under the 2006 and 2016 Equity Incentive Plans:



			Options Outstanding
	Options Outstanding		Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2017	2,601,181		$	12.24	7.17	$	113,958
Options granted	366,928		$	68.32
Options exercised	(798,424	)	$	7.19
Options forfeited	(75,548	)	$	34.30
Balance at December 31, 2018	2,094,137		$	23.20	7.02	$	97,976
Options granted	20,010		$	82.77
Options exercised	(426,655	)	$	9.98
Options forfeited	(61,865	)	$	53.96
Balances at September 30, 2019	1,625,627		$	26.23	6.37	$	78,664
Options exercisable – September 30, 2019	1,191,485		$	17.54	5.82	$	67,568
Options vested and expected to vest – September 30, 2019	1,605,077		$	25.82	6.35	$	78,284

The aggregate intrinsic values of options outstanding, exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the closing price of the Company’s common stock.

During the nine months ended September 30, 2019 and 2018, the Company granted options with a weighted-average grant date fair value of $38.29 and $32.23 per share, respectively.

Stock-Based Compensation

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Employee Stock Options Valuation

The fair value of employee and director stock options was estimated at the date of grant using the Black-Scholes option pricing model valuation model with the weighted average assumptions below.



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Expected term (in years)	0.0		6.1		6.1		6.1
Expected volatility	—	%	44.7	%	45.0	%	45.8	%
Risk-free interest rate	—	%	2.85	%	2.39	%	2.74	%
Dividend yield	—	%	—	%	—	%	—	%

The Company did not grant stock options during the three months ended September 30, 2019.

Stock-Based Compensation

The following table summarizes the total stock-based compensation expense included in the statements of operations and comprehensive loss for all periods presented (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Cost of revenue	$	—	$	86	$	225	$	224
Research and development	1,242		801		3,366		2,158
Selling, general and administrative	6,159		3,324		15,473		9,152
Total stock-based compensation expense	$	7,401	$	4,211	$	19,064	$	11,534

As of September 30, 2019, there was total unamortized compensation costs of $10.3 million, net of estimated forfeitures, related to unvested stock options which the Company expects to recognize over a period of approximately 1.9 years, $47.9 million, net of estimated forfeitures, related to unrecognized restricted stock unit (“RSU”) expense, which the Company expects to recognize over a period of 2.5 years, and $1.4 million unrecognized ESPP expense, which the Company will recognize over 0.7 years.

Performance based RSUs (“PRSU”)

In February 2019, the Company granted PRSUs to key executives of the Company. The performance equity program has a 2-year performance period measuring target revenue compound annual growth rate (“CAGR”) achievement for fiscal year 2020 compared to fiscal year 2018. There is a minimum performance threshold of 75% to earn 50% of target, and a maximum threshold of 125% achieved to earn 200% of target. The exact number of earned shares will be determined based on linear interpolation using the actual revenue CAGR as it falls between the minimum and maximum thresholds outlined above. The fair value of the PRSUs will be up to $18.5 million, depending on the actual achievement relative to the performance target. Based on management’s assessment at September 30, 2019 of the Company’s achievement of its performance targets, the Company has determined that it is probable that the performance targets will be achieved. As of September 30, 2019, management believes that it will achieve its performance targets at the 134% level, and has recognized cumulative PRSU expense of $3.3 million, for the nine months ended September 30, 2019.

Revision of Prior Period Financial Statements

9 Months Ended

Sep. 30, 2019

Accounting Changes and Error Corrections [Abstract]

Revision of Prior Period Financial Statements

As discussed in Note 1, the Company has revised certain prior period financial statements to correct immaterial errors in its accounting for revenues, contractual allowances, allowance for doubtful accounts and certain other items as presented below (in thousands, except share data):

Revised Consolidated Balance Sheets



	As of June 30, 2019
	As Reported			Adjustment			As Revised
Assets
Cash and cash equivalents	$	16,154		$	(170	)	$	15,984
Accounts receivable, net	29,137			(2,444		)	26,693
Prepaid expenses and other current assets	3,669			(141		)	3,528
Total current assets	94,974			(2,755		)	92,219
Property and equipment, net	12,618			826			13,444
Operating lease right-of-use assets	94,326			(83		)	94,243
Other assets	4,515			(18		)	4,497
Total assets	207,295			(2,030		)	205,265
Liabilities and Stockholders’ Equity
Current liabilities:
Accrued liabilities	23,304			58			23,362
Deferred revenue	1,199			(118		)	1,081
Operating lease liabilities, current portion	7,384			(224		)	7,160
Total current liabilities	35,654			(284		)	35,370
Operating lease liabilities, noncurrent portion	88,106			110			88,216
Total liabilities	158,687			(174		)	158,513
Additional paid-in capital	271,551			(82		)	271,469
Accumulated other comprehensive income	35			25			60
Accumulated deficit	(223,001		)	(1,799		)	(224,800		)
Total stockholders’ equity	48,608			(1,856		)	46,752
Total liabilities and stockholders’ equity	207,295			(2,030		)	205,265



	As of March 31, 2019
	As Reported			Adjustment			As Revised
Assets
Cash and cash equivalents	$	28,235		$	(134	)	$	28,101
Accounts receivable, net	28,252			(1,481		)	26,771
Prepaid expenses and other current assets	3,810			(140		)	3,670
Total current assets	93,308			(1,755		)	91,553
Property and equipment, net	10,208			70			10,278
Operating lease right-of-use assets	9,232			(270		)	8,962
Total assets	117,184			(1,955		)	115,229
Liabilities and Stockholders’ Equity
Accrued liabilities	20,099			437			20,536
Deferred revenue	1,309			(47		)	1,262
Operating lease liabilities, current portion	5,052			(211		)	4,841
Total current liabilities	28,549			179			28,728
Operating lease liabilities, noncurrent portion	3,990			(59		)	3,931
Total liabilities	67,461			120			67,581
Additional paid-in capital	261,231			441			261,672
Accumulated other comprehensive income	2			25			27
Accumulated deficit	(211,534		)	(2,541		)	(214,075		)
Total stockholders’ equity	49,723			(2,075		)	47,648
Total liabilities and stockholders’ equity	117,184			(1,955		)	115,229



	As of December 31, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	21,977		$	(2,187	)	$	19,790
Total current assets	106,482			(2,187		)	104,295
Total assets	119,710			(2,187		)	117,523
Liabilities and Stockholders’ Equity
Accrued liabilities	26,570			118			26,688
Deferred revenue	1,243			(20		)	1,223
Total current liabilities	30,236			98			30,334
Total liabilities	65,288			98			65,386
Accumulated other comprehensive loss	(41		)	25			(16		)
Accumulated deficit	(203,515		)	(2,310		)	(205,825		)
Total stockholders’ equity	54,422			(2,285		)	52,137
Total liabilities and stockholders’ equity	119,710			(2,187		)	117,523



	As of September 30, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	20,465		$	(490	)	$	19,975
Total current assets	106,731			(490		)	106,241
Total assets	118,989			(490		)	118,499
Liabilities and Stockholders’ Equity
Accrued liabilities	19,178			269			19,447
Deferred revenue	1,174			(15		)	1,159
Total current liabilities	22,263			254			22,517
Total liabilities	55,031			254			55,285
Accumulated other comprehensive income	(29		)	10			(19		)
Accumulated deficit	(188,801		)	(754		)	(189,555		)
Total stockholders’ equity	63,958			(744		)	63,214
Total liabilities and stockholders’ equity	118,989			(490		)	118,499



	As of June 30, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	19,065		$	(1,064	)	$	18,001
Total current assets	109,656			(1,064		)	108,592
Property and equipment, net	7,560			34			7,594
Total assets	120,918			(1,030		)	119,888
Liabilities and Stockholders’ Equity
Accrued liabilities	16,355			240			16,595
Total current liabilities	19,655			240			19,895
Total liabilities	52,452			240			52,692
Accumulated deficit	(178,558		)	(1,270		)	(179,828		)
Total stockholders’ equity	68,466			(1,270		)	67,196
Total liabilities and stockholders’ equity	120,918			(1,030		)	119,888



	As of March 31, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	17,165		$	(25	)	$	17,140
Total current assets	111,542			(25		)	111,517
Total assets	122,321			(25		)	122,296
Liabilities and Stockholders’ Equity
Accrued liabilities	12,658			147			12,805
Total current liabilities	16,938			147			17,085
Total liabilities	49,698			147			49,845
Accumulated deficit	(166,352		)	(172		)	(166,524		)
Total stockholders’ equity	72,623			(172		)	72,451
Total liabilities and stockholders’ equity	122,321			(25		)	122,296



	As of December 31, 2017
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	12,953		$	181		$	13,134
Total current assets	119,581			181			119,762
Property and equipment, net	6,221			75			6,296
Total assets	133,123			256			133,379
Liabilities and Stockholders’ Equity
Accrued liabilities	15,644			468			16,112
Total current liabilities	20,918			468			21,386
Total liabilities	53,570			468			54,038
Accumulated deficit	(156,589		)	(212		)	(156,801		)
Total stockholders' equity	79,553			(212		)	79,341
Total liabilities and stockholders’ equity	133,123			256			133,379

Revised Consolidated Statements of Operations



	Three months ended June 30, 2019									Six months ended June 30, 2019
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	53,331		$	(890	)	$	52,441		$	100,545		$	230		$	100,775
Cost of revenue	12,825			187			13,012			24,555			230			24,785
Gross profit	40,506			(1,077		)	39,429			75,990			—			75,990
Research and development	8,639			(806		)	7,833			15,395			(863		)	14,532
Selling, general and administrative	43,189			(1,028		)	42,161			79,894			333			80,227
Total operating expenses	51,828			(1,834		)	49,994			95,289			(530		)	94,759
Loss from operations	(11,322		)	757			(10,565		)	(19,299		)	530			(18,769		)
Other income, net	310			(15		)	295			689			(19		)	670
Loss before income taxes	(11,452		)	742			(10,710		)	(19,459		)	511			(18,948		)
Net loss	(11,467		)	742			(10,725		)	(19,486		)	511			(18,975		)
Net loss per common share, basic and diluted	(0.46		)	0.03			(0.43		)	(0.79		)	0.02			(0.77		)



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Revenue	$	47,214		$	1,120		$	48,334
Cost of revenue	11,730			43			11,773
Gross profit	35,484			1,077			36,561
Research and development	6,756			(57		)	6,699
Selling, general and administrative	36,705			1,361			38,066
Total operating expenses	43,461			1,304			44,765
Loss from operations	(7,977		)	(227		)	(8,204		)
Other income, net	379			(4		)	375
Loss before income taxes	(8,007		)	(231		)	(8,238		)
Net loss	(8,019		)	(231		)	(8,250		)
Net loss per common share, basic and diluted	(0.33		)	(0.01		)	(0.34		)



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Revenue	$	147,293		$	(16	)	$	147,277
Cost of revenue	38,579			216			38,795
Gross profit	108,714			(232		)	108,482
Research and development	20,750			110			20,860
Selling, general and administrative	131,582			1,731			133,313
Total operating expenses	152,332			1,841			154,173
Loss from operations	(43,618		)	(2,073		)	(45,691		)
Other income, net	1,526			(25		)	1,501
Loss before income taxes	(48,236		)	(2,098		)	(50,334		)
Net loss	(48,280		)	(2,098		)	(50,378		)
Net loss per common share, basic and diluted	(2.02		)	(0.09		)	(2.11		)



	Three months ended September 30, 2018									Nine months ended September 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	38,104		$	337		$	38,441		$	104,138		$	1,357		$	105,495
Cost of revenue	9,949			4			9,953			28,050			(61		)	27,989
Gross profit	28,155			333			28,488			76,088			1,418			77,506
Research and development	5,164			(78		)	5,086			13,747			29			13,776
Selling, general and administrative	32,739			(116		)	32,623			94,410			1,920			96,330
Total operating expenses	37,903			(194		)	37,709			108,157			1,949			110,106
Loss from operations	(9,748		)	527			(9,221		)	(32,069		)	(531		)	(32,600		)
Other income, net	365			(10		)	355			1,082			(10		)	1,072
Loss before income taxes	(10,244		)	517			(9,727		)	(33,567		)	(541		)	(34,108		)
Net loss	(10,244		)	517			(9,727		)	(33,567		)	(541		)	(34,108		)
Net loss per common share, basic and diluted	(0.43		)	0.03			(0.40		)	(1.41		)	(0.03		)	(1.44		)



	Three months ended June 30, 2018									Six months ended June 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	35,469		$	(177	)	$	35,292		$	66,034		$	1,020		$	67,054
Cost of revenue	9,490			(4		)	9,486			18,101			(65		)	18,036
Gross profit	25,979			(173		)	25,806			47,933			1,085			49,018
Research and development	4,564			83			4,647			8,583			107			8,690
Selling, general and administrative	33,094			846			33,940			61,671			2,036			63,707
Total operating expenses	37,658			929			38,587			70,254			2,143			72,397
Loss from operations	(11,679		)	(1,102		)	(12,781		)	(22,321		)	(1,058		)	(23,379		)
Other income, net	334			4			338			717			—			717
Net loss	(12,206		)	(1,098		)	(13,304		)	(23,323		)	(1,058		)	(24,381		)
Net loss per common share, basic and diluted	(0.51		)	(0.05		)	(0.56		)	(0.99		)	(0.04		)	(1.03		)



	Three months ended March 31, 2018
	As Reported			Adjustment			As Revised
Revenue	$	30,565		$	1,197		$	31,762
Cost of revenue	8,611			(61		)	8,550
Gross profit	21,954			1,258			23,212
Research and development	4,019			24			4,043
Selling, general and administrative	28,577			1,190			29,767
Total operating expenses	32,596			1,214			33,810
Loss from operations	(10,642		)	44			(10,598		)
Other income, net	383			(4		)	379
Net loss	(11,117		)	40			(11,077		)



	Year ended December 31, 2017
	As Reported			Adjustment			As Revised
Revenue	$	98,509		$	620		$	99,129
Cost of revenue	27,708			495			28,203
Gross profit	70,801			125			70,926
Research and development	13,335			(70		)	13,265
Selling, general and administrative	84,737			515			85,252
Total operating expenses	98,072			445			98,517
Loss from operations	(27,271		)	(320		)	(27,591		)
Net loss	(29,420		)	(320		)	(29,740		)
Net loss per common share, basic and diluted	(1.30		)	(0.01		)	(1.31		)

Revised Consolidated Statements of Comprehensive Income (Loss)



	Three months ended June 30, 2019								Six months ended June 30, 2019
	As Reported			Adjustment		As Revised			As Reported			Adjustment		As Revised
Net loss	$	(11,467	)	$	742	$	(10,725	)	$	(19,486	)	$	511	$	(18,975	)
Comprehensive loss	(11,434		)	742		(10,692		)	(19,410		)	511		(18,899		)



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Net loss	$	(8,019	)	$	(231	)	$	(8,250	)
Comprehensive loss	(7,976		)	(231		)	(8,207		)



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Net loss	$	(48,280	)	$	(2,098	)	$	(50,378	)
Net change in unrealized gains on available-for-sale securities	24			25			49
Comprehensive loss	(48,256		)	(2,073		)	(50,329		)



	Three months ended September 30, 2018								Nine months ended September 30, 2018
	As Reported			Adjustment		As Revised			As Reported			Adjustment			As Revised
Net loss	$	(10,244	)	$	517	$	(9,727	)	$	(33,567	)	$	(541	)	$	(34,108	)
Net change in unrealized losses on available-for-sale securities	19			—		19			(83		)	129			46
Foreign currency translation	(10		)	10		—			(10		)	10			—
Comprehensive loss	(10,235		)	527		(9,708		)	(33,660		)	(402		)	(34,062		)



	Three months ended June 30, 2018									Six months ended June 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Net loss	$	(12,206	)	$	(1,098	)	$	(13,304	)	$	(23,323	)	$	(1,058	)	$	(24,381	)
Comprehensive loss	(12,159		)	(1,098		)	(13,257		)	(23,296		)	(1,058		)	(24,354		)



	Three months ended March 31, 2018
	As Reported			Adjustment		As Revised
Net loss	$	(11,117	)	$	40	$	(11,077	)
Comprehensive loss	(11,137		)	40		(11,097		)



	Year ended December 31, 2017
	As Reported			Adjustment			As Revised
Net loss	$	(29,420	)	$	(320	)	$	(29,740	)
Comprehensive loss	(29,476		)	(320		)	(29,796		)

Revised Consolidated Statements of Cash Flows



	Six months ended June 30, 2019
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(19,486	)	$	511		$	(18,975	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,292			18			1,310
Stock-based compensation	11,745			(82		)	11,663
Provision for doubtful accounts and contractual allowances	10,683			1,687			12,370
Amortization of operating lease right-of-use assets	5,061			83			5,144
Changes in operating assets and liabilities:
Accounts receivable	(17,844		)	(1,570		)	(19,414		)
Prepaid expenses and other current assets	(27		)	263			236
Other assets	(1,174		)	18			(1,156		)
Accounts payable	1,025			(6		)	1,019
Accrued liabilities	(3,187		)	(70		)	(3,257		)
Deferred revenue	(45		)	(98		)	(143		)
Operating lease liabilities	(3,724		)	(114		)	(3,838		)
Net cash used in operating activities	(16,781		)	639			(16,142		)
Cash flows from investing activities
Purchases of property and equipment	(4,468		)	(809		)	(5,277		)
Net cash provided by investing activities	11,106			(809		)	10,297
Net increase in cash, cash equivalents, and restricted cash	(3,869		)	(170		)	(4,039		)
Cash, cash equivalents and restricted cash end of period	16,154			(170		)	15,984
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	284			16			300



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(8,019	)	$	(231	)	$	(8,250	)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,415			441			4,856
Provision for doubtful accounts and contractual allowances	4,709			702			5,411
Changes in operating assets and liabilities:
Accounts receivable	(10,984		)	(1,408		)	(12,392		)
Prepaid expenses and other current assets	(169		)	140			(29		)
Accrued liabilities	(6,380		)	319			(6,061		)
Deferred revenue	66			(27		)	39
Net cash used in operating activities	(17,099		)	(64		)	(17,163		)
Cash flows from investing activities
Purchases of property and equipment	(1,635		)	(70		)	(1,705		)
Net cash provided by investing activities	26,449			(70		)	26,379
Net increase in cash, cash equivalents, and restricted cash	8,212			(134		)	8,078
Cash and cash equivalents end of period	28,235			(134		)	28,101



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(48,280	)	$	(2,098	)	$	(50,378	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	15,218			1,230			16,448
Changes in operating assets and liabilities:
Accounts receivable	(22,885		)	1,138			(21,747		)
Accrued liabilities	10,776			(275		)	10,501
Deferred revenue	5			(20		)	(15		)
Net cash used in operating activities	(29,068		)	(25		)	(29,093		)
Cash flows from investing activities
Purchases of available-for-sale investments	(93,158		)	25			(93,133		)
Net cash provided by investing activities	34,117			25			34,142



	Nine months ended September 30, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(33,567	)	$	(541	)	$	(34,108	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	8,921			671			9,592
Changes in operating assets and liabilities:
Accounts receivable	(15,088		)	10			(15,078		)
Accrued liabilities	3,335			(125		)	3,210
Deferred revenue	(64		)	(15		)	(79		)



	Six months ended June 30, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(23,323	)	$	(1,058	)	$	(24,381	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	6,440			1,245			7,685
Changes in operating assets and liabilities:
Accrued liabilities	497			(186		)	311
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	218			34			252



	Three months ended March 31, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(11,117	)	$	40		$	(11,077	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	2,680			206			2,886
Changes in operating assets and liabilities:
Accrued liabilities	(2,977		)	(246		)	(3,223		)



	Year ended December 31, 2017
	As Reported		Adjustment		As Revised
Cash flows from operating activities
Net loss	(29,420	)	(320	)	(29,740	)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	10,123		(371	)	9,752
Provision for doubtful accounts and contractual allowances	9,403		(181	)	9,222
Changes in operating assets and liabilities:
Accounts receivable	(12,950	)	479		(12,471	)
Accrued liabilities	5,364		393		5,757
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	35		75		110

Revised Consolidated Statements of Shareholder's Equity



	Six months ended June 30, 2019
	As Reported			Adjustment			As Revised
Stock-based compensation expense	$	11,745		$	(82	)	$	11,663
Additional-paid-in-capital ending balance	271,551			(82		)	271,469
Accumulated other comprehensive loss beginning balance	(41		)	25			(16		)
Accumulated other comprehensive loss ending balance	35			25			60
Accumulated deficit beginning balance	(203,515		)	(2,310		)	(205,825		)
Net loss	(19,486		)	511			(18,975		)
Accumulated deficit ending balance	(223,001		)	(1,799		)	(224,800		)
Total stockholders' equity	48,608			(1,856		)	46,752



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Stock-based compensation expense	$	4,415		$	441		$	4,856
Additional-paid-in-capital ending balance	261,231			441			261,672
Accumulated other comprehensive loss beginning balance	(41		)	25			(16		)
Accumulated other comprehensive loss ending balance	2			25			27
Accumulated deficit beginning balance	(203,515		)	(2,310		)	(205,825		)
Net loss	(8,019		)	(231		)	(8,250		)
Accumulated deficit ending balance	(211,534		)	(2,541		)	(214,075		)
Total stockholders' equity	49,723			(2,075		)	47,648



	Year Ended December 31, 2018
	As Reported			Adjustment			As Revised
Unrealized loss on investments	$	24		$	25		$	49
Accumulated other comprehensive loss ending balance	(41		)	25			(16		)
Accumulated deficit beginning balance	(156,589		)	(212		)	(156,801		)
Net loss	(48,280		)	(2,098		)	(50,378		)
Accumulated deficit ending balance	(203,515		)	(2,310		)	(205,825		)
Total stockholders' equity	54,422			(2,285		)	52,137



	Six Months Ended June 30, 2018
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(156,589	)	$	(212	)	$	(156,801	)
Net loss	(23,323		)	(1,058		)	(24,381		)
Accumulated deficit ending balance	(178,558		)	(1,270		)	(179,828		)
Total stockholders' equity	68,466			(1,270		)	67,196



	Three Months Ended March 31, 2018
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(156,589	)	$	(212	)	$	(156,801	)
Net loss	(11,117		)	40			(11,077		)
Accumulated deficit ending balance	(166,352		)	(172		)	(166,524		)
Total stockholders' equity	72,623			(172		)	72,451



	Year Ended December 31, 2017
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(127,169	)	$	108		$	(127,061	)
Net loss	(29,420		)	(320		)	(29,740		)
Accumulated deficit ending balance	(156,589		)	(212		)	(156,801		)
Total stockholders' equity	79,553			(212		)	79,341

Summary of Significant Accounting Policies (Policies)

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Basis of Presentation

Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowance

Concentration of Credit Risk

Concentrations of Risk

Credit Risk

doubtful accounts when it becomes probable that a receivable will not be collected.

Revenue Recognition

A summary of the payment arrangements with third-party payors and healthcare institutions is as follows:


•	Contracted third-party payors – The Company has contracts with negotiated prices for services provided for patients with commercial healthcare insurance carriers.


•	CMS – The Company has received independent diagnostic testing facility approval from regional Medicare Administrative Contractors and will receive reimbursement per the relevant Current Procedural Terminology (“CPT”) code rate for the services rendered to the patient covered by CMS.


•	Non-contracted third-party payors: Non-contracted commercial and government payors often reimburse out-of-network rates provided under the relevant CPT codes on a case-by-case basis. The transaction price is based on factors including an average of the Company’s historical collection experience for non-contracted services. This rate is reviewed at least quarterly.


•	Healthcare institutions – Healthcare institutions are typically hospitals or physician practices in which the Company has negotiated amounts for its monitoring services, including certain governmental agencies such as the Veteran’s Administration and Department of Defense.

Disaggregation of Revenue

Contract Liabilities

Contract Costs

Leases

Identifying a lease


•	The right to obtain substantially all of the economic benefits from use of the identified asset; and


•	The right to direct the use of the identified asset.

Discount rate for leases

Lease term

Lease Modification

Recently Adopted Accounting Guidance

September 2019.

Recently Adopted Accounting Guidance


•	The package of three practical expedients, which allows entities to make an election that allows them not to reassess (1) whether existing or expired contracts contain embedded leases under Topic 842, (2) lease classification of existing or expiring leases, and (3) indirect costs for existing or expired leases;


•	Combining lease and non-lease components practical expedient, which allows lessees, as an accounting policy election by class of underlying asset, to choose not to separate non-lease components from lease components and instead to account for each separate lease component and the non-lease components associated with that lease component as a single lease component; and


•	Comparative reporting practical expedient, which allows entities to initially apply Topic 842 at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption.

For further details, refer to Note 6. Commitments and Contingencies.

Recent Accounting Standards or Updates Not Yet Effective

Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2019

Accounting Policies [Abstract]

Schedule of Changes in Allowance for Doubtful Accounts

The following table presents the changes in the allowance for doubtful accounts (in thousands):



	Nine Months Ended September 30, 2019			Year Ended December 31, 2018
Balance, beginning of period	$	7,296		$	4,486
Add: provision for doubtful accounts	6,473			7,353
Less: write-offs, net of recoveries and other adjustments	(6,439		)	(4,543		)
Balance, end of period	$	7,330		$	7,296

Schedule of Changes in Contractual Allowance

The following table presents the changes in the contractual allowance (in thousands):



	Nine Months Ended September 30, 2019			Year Ended December 31, 2018
Balance, beginning of period	$	9,205		$	6,345
Add: provision for contractual allowances	11,108			9,095
Less: realized contractual adjustments	(7,162		)	(6,235		)
Balance, end of period	$	13,151		$	9,205

Disaggregated Revenue by Payor Type and Major Service

Disaggregated revenue by payor type and major service line for three and nine months ended September 30, 2019 and September 30, 2018 were as follows (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Contracted third-party payors	$	25,961	$	14,887	$	72,040	$	38,270
Non-contracted third-party payors	2,686		3,126		9,016		10,302
Centers for Medicare & Medicaid	15,379		10,952		42,573		29,317
Healthcare Institutions	10,647		9,476		31,819		27,606
Total	$	54,673	$	38,441	$	155,448	$	105,495

Cash Equivalents and Investments (Tables)

9 Months Ended

Sep. 30, 2019

Cash Equivalents And Investments [Abstract]

Schedule of Cash Equivalents and Available For Sale Investments

The fair value of cash equivalents and available-for-sale investments at September 30, 2019 and December 31, 2018, were as follows (in thousands):



	September 30, 2019
	Amortized Cost		Gross Unrealized					Estimated Fair Value
	Amortized Cost		Gains		Losses			Estimated Fair Value
Money market funds	$	24,034	$	—	$	—		$	24,034
U.S. government securities	85,435		34		—			85,469
Corporate notes	15,017		6		(1		)	15,022
Commercial paper	34,592		—		—			34,592
Total cash equivalents and available-for-sale investments	$	159,078	$	40	$	(1	)	$	159,117
Classified as:
Cash equivalents								$	32,000
Short-term investments								118,091
Long-term investments								9,026
Total cash equivalents and available-for-sale investments								$	159,117
	December 31, 2018
	Amortized Cost		Gross Unrealized					Estimated Fair Value
	Amortized Cost		Gains		Losses			Estimated Fair Value
Money market funds	$	10,606	$	—	$	—		$	10,606
U.S. government securities	9,976		—		(1		)	9,975
Corporate notes	16,514		3		(18		)	16,499
Commercial paper	36,331		—		—			36,331
Total cash equivalents and available-for-sale investments	$	73,427	$	3	$	(19	)	$	73,411
Classified as:
Cash equivalents								$	15,091
Short-term investments								58,320
Total cash equivalents and available-for-sale investments								$	73,411

Schedule of Fair Value of Short-term and Long-term Marketable Securities Classified by Maturity

The following table summarizes the fair value of the Company’s cash equivalents, short-term and long-term marketable securities classified by maturity (in thousands):



	September 30, 2019		December 31, 2018
Due within one year	$	150,091	$	73,411
Due after one year through three years	9,026		—
Total cash equivalents and available-for-sale investments	$	159,117	$	73,411

Schedule of Available-for-Sale Securities Unrealized Loss Position

The following tables present the Company's available-for-sale securities that were in an unrealized position as of December 31, 2018 (in thousands):



	December 31, 2018
	Less than 12 months					12 Months or Greater					Total
Assets	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss			Fair Value		Unrealized Loss
U.S. government securities	$	5,977	$	(1	)	$	—	$	—		$	5,977	$	(1	)
Corporate notes	11,521		(10		)	2,993		(8		)	14,514		(18		)
Total	$	17,498	$	(11	)	$	2,993	$	(8	)	$	20,491	$	(19	)

Balance Sheet Components (Tables)

9 Months Ended

Sep. 30, 2019

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Components of Inventory and Printed Circuit Board Assemblies ("PCBAs")

Inventory consisted of the following (in thousands):



	September 30, 2019		December 31, 2018
Raw materials	$	1,341	$	676
Finished goods	2,158		1,386
Total	$	3,499	$	2,062

Components of Property and Equipment, Net

Property and equipment, net consisted of the following (in thousands):



	September 30, 2019			December 31, 2018
Laboratory and manufacturing equipment	$	4,050		$	2,750
Computer equipment and software	1,062			1,062
Furniture and fixtures	724			925
Leasehold improvements	4,921			726
Internal-use software	13,761			8,925
Total property and equipment, gross	24,518			14,388
Less: accumulated depreciation and amortization	(6,715		)	(5,230		)
Total property and equipment, net	$	17,803		$	9,158

Components of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):



	September 30, 2019		December 31, 2018
Accrued vacation	$	3,571	$	2,825
Accrued payroll and related expenses	14,107		18,188
Accrued ESPP contribution	1,656		373
Accrued professional services fees	820		1,249
Claims payable	2,991		2,374
Verily collaboration agreement	5,000		—
Other	4,082		1,679
Total accrued liabilities	$	32,227	$	26,688

Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2019

Equity [Abstract]

Schedule of Common Stock Shares Reserved for Future Issuance

The Company had reserved shares of common stock for issuance as follows:



	September 30, 2019	December 31, 2018
Options issued and outstanding	1,625,627	2,094,137
Unvested restricted stock units	881,516	547,891
Common stock warrants issued and outstanding	2,006	4,857
Shares available for grant under future stock plans	6,746,886	5,607,014
Shares available for future issuance	9,256,035	8,253,899

- Definition

Tabular disclosure of an entity's stock, including par or stated value per share, number and dollar amount of share subscriptions, shares authorized, shares issued, shares outstanding, number and dollar amount of shares held in an employee trust, dividend per share, total dividends, share conversion features, par value plus additional paid in capital, the value of treasury stock and other information necessary to a fair presentation, and EPS information. Stock by class includes common, convertible, and preferred stocks which are not redeemable or redeemable solely at the option of the issuer. Includes preferred stock with redemption features that are solely within the control of the issuer and mandatorily redeemable stock if redemption is required to occur only upon liquidation or termination of the reporting entity. If more than one issue is outstanding, state the title of each issue and the corresponding dollar amount; dollar amount of any shares subscribed but unissued and the deduction of subscriptions receivable there from; number of shares authorized, issued, and outstanding.

+ References

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+ Details

Equity Incentive Plans (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Summary of Share-based Awards Available for Grant under 2016 Plan

A summary of share-based awards available for grant under the 2016 Equity Incentive Plan is as follows:



	Awards Available for Grant
Balance at December 31, 2017	4,034,152
Additional awards authorized	1,168,865
Awards granted	(666,913	)
Awards forfeited	124,478
Awards withheld for tax purposes	56,710
Balance at December 31, 2018	4,717,292
Additional awards authorized	1,218,402
Awards granted	(620,624	)
Awards forfeited	155,253
Awards withheld for tax purposes	58,341
Balance at September 30, 2019	5,528,664

Summary of Stock Option Activity Under 2006 and 2016 Plans

The following table summarizes stock option activity under the 2006 and 2016 Equity Incentive Plans:



			Options Outstanding
	Options Outstanding		Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2017	2,601,181		$	12.24	7.17	$	113,958
Options granted	366,928		$	68.32
Options exercised	(798,424	)	$	7.19
Options forfeited	(75,548	)	$	34.30
Balance at December 31, 2018	2,094,137		$	23.20	7.02	$	97,976
Options granted	20,010		$	82.77
Options exercised	(426,655	)	$	9.98
Options forfeited	(61,865	)	$	53.96
Balances at September 30, 2019	1,625,627		$	26.23	6.37	$	78,664
Options exercisable – September 30, 2019	1,191,485		$	17.54	5.82	$	67,568
Options vested and expected to vest – September 30, 2019	1,605,077		$	25.82	6.35	$	78,284

Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Schedule of Fair Value of Employee and Director Stock Options Estimated Using Weighted Average Assumptions

The fair value of employee and director stock options was estimated at the date of grant using the Black-Scholes option pricing model valuation model with the weighted average assumptions below.



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Expected term (in years)	0.0		6.1		6.1		6.1
Expected volatility	—	%	44.7	%	45.0	%	45.8	%
Risk-free interest rate	—	%	2.85	%	2.39	%	2.74	%
Dividend yield	—	%	—	%	—	%	—	%

Summary of Total Stock-Based Compensation Expense Included in Statements of Operations and Comprehensive Loss

The following table summarizes the total stock-based compensation expense included in the statements of operations and comprehensive loss for all periods presented (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Cost of revenue	$	—	$	86	$	225	$	224
Research and development	1,242		801		3,366		2,158
Selling, general and administrative	6,159		3,324		15,473		9,152
Total stock-based compensation expense	$	7,401	$	4,211	$	19,064	$	11,534

Net Loss Per Common Share (Tables)

9 Months Ended

Sep. 30, 2019

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss per Share Attributable to Common Stock holders

The following table sets forth the computation of the basic and diluted net loss per share (in thousands, except share and per share data):



	Three Months Ended September 30,						Nine Months Ended September 30,
	2019			2018			2019			2018
Numerator:
Net loss	$	(18,293	)	$	(9,727	)	$	(37,268	)	$	(34,108	)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted	25,247,831			24,059,010			24,818,482			23,764,153
Net loss per common share, basic and diluted	$	(0.72	)	$	(0.40	)	$	(1.50	)	$	(1.44	)

Schedule of Anti-dilutive Securities Excluded from Diluted Net Loss per Common Share

The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per common share for the nine months ended September 30, 2019 and 2018, because their inclusion would be anti-dilutive:



	Nine Months Ended, September 30
	2019	2018
Options to purchase common stock	1,625,627	2,205,126
PRSUs and RSUs issued and unvested	881,516	605,985
Warrants to purchase common stock	2,006	4,857
Total	2,509,149	2,815,968

Revision of Prior Period Financial Statements (Tables)

9 Months Ended

Sep. 30, 2019

Accounting Changes and Error Corrections [Abstract]

Schedule of Revised Consolidated Statements

Revised Consolidated Balance Sheets



	As of June 30, 2019
	As Reported			Adjustment			As Revised
Assets
Cash and cash equivalents	$	16,154		$	(170	)	$	15,984
Accounts receivable, net	29,137			(2,444		)	26,693
Prepaid expenses and other current assets	3,669			(141		)	3,528
Total current assets	94,974			(2,755		)	92,219
Property and equipment, net	12,618			826			13,444
Operating lease right-of-use assets	94,326			(83		)	94,243
Other assets	4,515			(18		)	4,497
Total assets	207,295			(2,030		)	205,265
Liabilities and Stockholders’ Equity
Current liabilities:
Accrued liabilities	23,304			58			23,362
Deferred revenue	1,199			(118		)	1,081
Operating lease liabilities, current portion	7,384			(224		)	7,160
Total current liabilities	35,654			(284		)	35,370
Operating lease liabilities, noncurrent portion	88,106			110			88,216
Total liabilities	158,687			(174		)	158,513
Additional paid-in capital	271,551			(82		)	271,469
Accumulated other comprehensive income	35			25			60
Accumulated deficit	(223,001		)	(1,799		)	(224,800		)
Total stockholders’ equity	48,608			(1,856		)	46,752
Total liabilities and stockholders’ equity	207,295			(2,030		)	205,265



	As of March 31, 2019
	As Reported			Adjustment			As Revised
Assets
Cash and cash equivalents	$	28,235		$	(134	)	$	28,101
Accounts receivable, net	28,252			(1,481		)	26,771
Prepaid expenses and other current assets	3,810			(140		)	3,670
Total current assets	93,308			(1,755		)	91,553
Property and equipment, net	10,208			70			10,278
Operating lease right-of-use assets	9,232			(270		)	8,962
Total assets	117,184			(1,955		)	115,229
Liabilities and Stockholders’ Equity
Accrued liabilities	20,099			437			20,536
Deferred revenue	1,309			(47		)	1,262
Operating lease liabilities, current portion	5,052			(211		)	4,841
Total current liabilities	28,549			179			28,728
Operating lease liabilities, noncurrent portion	3,990			(59		)	3,931
Total liabilities	67,461			120			67,581
Additional paid-in capital	261,231			441			261,672
Accumulated other comprehensive income	2			25			27
Accumulated deficit	(211,534		)	(2,541		)	(214,075		)
Total stockholders’ equity	49,723			(2,075		)	47,648
Total liabilities and stockholders’ equity	117,184			(1,955		)	115,229



	As of December 31, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	21,977		$	(2,187	)	$	19,790
Total current assets	106,482			(2,187		)	104,295
Total assets	119,710			(2,187		)	117,523
Liabilities and Stockholders’ Equity
Accrued liabilities	26,570			118			26,688
Deferred revenue	1,243			(20		)	1,223
Total current liabilities	30,236			98			30,334
Total liabilities	65,288			98			65,386
Accumulated other comprehensive loss	(41		)	25			(16		)
Accumulated deficit	(203,515		)	(2,310		)	(205,825		)
Total stockholders’ equity	54,422			(2,285		)	52,137
Total liabilities and stockholders’ equity	119,710			(2,187		)	117,523



	As of September 30, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	20,465		$	(490	)	$	19,975
Total current assets	106,731			(490		)	106,241
Total assets	118,989			(490		)	118,499
Liabilities and Stockholders’ Equity
Accrued liabilities	19,178			269			19,447
Deferred revenue	1,174			(15		)	1,159
Total current liabilities	22,263			254			22,517
Total liabilities	55,031			254			55,285
Accumulated other comprehensive income	(29		)	10			(19		)
Accumulated deficit	(188,801		)	(754		)	(189,555		)
Total stockholders’ equity	63,958			(744		)	63,214
Total liabilities and stockholders’ equity	118,989			(490		)	118,499



	As of June 30, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	19,065		$	(1,064	)	$	18,001
Total current assets	109,656			(1,064		)	108,592
Property and equipment, net	7,560			34			7,594
Total assets	120,918			(1,030		)	119,888
Liabilities and Stockholders’ Equity
Accrued liabilities	16,355			240			16,595
Total current liabilities	19,655			240			19,895
Total liabilities	52,452			240			52,692
Accumulated deficit	(178,558		)	(1,270		)	(179,828		)
Total stockholders’ equity	68,466			(1,270		)	67,196
Total liabilities and stockholders’ equity	120,918			(1,030		)	119,888



	As of March 31, 2018
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	17,165		$	(25	)	$	17,140
Total current assets	111,542			(25		)	111,517
Total assets	122,321			(25		)	122,296
Liabilities and Stockholders’ Equity
Accrued liabilities	12,658			147			12,805
Total current liabilities	16,938			147			17,085
Total liabilities	49,698			147			49,845
Accumulated deficit	(166,352		)	(172		)	(166,524		)
Total stockholders’ equity	72,623			(172		)	72,451
Total liabilities and stockholders’ equity	122,321			(25		)	122,296



	As of December 31, 2017
	As Reported			Adjustment			As Revised
Assets
Accounts receivable, net	$	12,953		$	181		$	13,134
Total current assets	119,581			181			119,762
Property and equipment, net	6,221			75			6,296
Total assets	133,123			256			133,379
Liabilities and Stockholders’ Equity
Accrued liabilities	15,644			468			16,112
Total current liabilities	20,918			468			21,386
Total liabilities	53,570			468			54,038
Accumulated deficit	(156,589		)	(212		)	(156,801		)
Total stockholders' equity	79,553			(212		)	79,341
Total liabilities and stockholders’ equity	133,123			256			133,379

Revised Consolidated Statements of Operations



	Three months ended June 30, 2019									Six months ended June 30, 2019
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	53,331		$	(890	)	$	52,441		$	100,545		$	230		$	100,775
Cost of revenue	12,825			187			13,012			24,555			230			24,785
Gross profit	40,506			(1,077		)	39,429			75,990			—			75,990
Research and development	8,639			(806		)	7,833			15,395			(863		)	14,532
Selling, general and administrative	43,189			(1,028		)	42,161			79,894			333			80,227
Total operating expenses	51,828			(1,834		)	49,994			95,289			(530		)	94,759
Loss from operations	(11,322		)	757			(10,565		)	(19,299		)	530			(18,769		)
Other income, net	310			(15		)	295			689			(19		)	670
Loss before income taxes	(11,452		)	742			(10,710		)	(19,459		)	511			(18,948		)
Net loss	(11,467		)	742			(10,725		)	(19,486		)	511			(18,975		)
Net loss per common share, basic and diluted	(0.46		)	0.03			(0.43		)	(0.79		)	0.02			(0.77		)



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Revenue	$	47,214		$	1,120		$	48,334
Cost of revenue	11,730			43			11,773
Gross profit	35,484			1,077			36,561
Research and development	6,756			(57		)	6,699
Selling, general and administrative	36,705			1,361			38,066
Total operating expenses	43,461			1,304			44,765
Loss from operations	(7,977		)	(227		)	(8,204		)
Other income, net	379			(4		)	375
Loss before income taxes	(8,007		)	(231		)	(8,238		)
Net loss	(8,019		)	(231		)	(8,250		)
Net loss per common share, basic and diluted	(0.33		)	(0.01		)	(0.34		)



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Revenue	$	147,293		$	(16	)	$	147,277
Cost of revenue	38,579			216			38,795
Gross profit	108,714			(232		)	108,482
Research and development	20,750			110			20,860
Selling, general and administrative	131,582			1,731			133,313
Total operating expenses	152,332			1,841			154,173
Loss from operations	(43,618		)	(2,073		)	(45,691		)
Other income, net	1,526			(25		)	1,501
Loss before income taxes	(48,236		)	(2,098		)	(50,334		)
Net loss	(48,280		)	(2,098		)	(50,378		)
Net loss per common share, basic and diluted	(2.02		)	(0.09		)	(2.11		)



	Three months ended September 30, 2018									Nine months ended September 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	38,104		$	337		$	38,441		$	104,138		$	1,357		$	105,495
Cost of revenue	9,949			4			9,953			28,050			(61		)	27,989
Gross profit	28,155			333			28,488			76,088			1,418			77,506
Research and development	5,164			(78		)	5,086			13,747			29			13,776
Selling, general and administrative	32,739			(116		)	32,623			94,410			1,920			96,330
Total operating expenses	37,903			(194		)	37,709			108,157			1,949			110,106
Loss from operations	(9,748		)	527			(9,221		)	(32,069		)	(531		)	(32,600		)
Other income, net	365			(10		)	355			1,082			(10		)	1,072
Loss before income taxes	(10,244		)	517			(9,727		)	(33,567		)	(541		)	(34,108		)
Net loss	(10,244		)	517			(9,727		)	(33,567		)	(541		)	(34,108		)
Net loss per common share, basic and diluted	(0.43		)	0.03			(0.40		)	(1.41		)	(0.03		)	(1.44		)



	Three months ended June 30, 2018									Six months ended June 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Revenue	$	35,469		$	(177	)	$	35,292		$	66,034		$	1,020		$	67,054
Cost of revenue	9,490			(4		)	9,486			18,101			(65		)	18,036
Gross profit	25,979			(173		)	25,806			47,933			1,085			49,018
Research and development	4,564			83			4,647			8,583			107			8,690
Selling, general and administrative	33,094			846			33,940			61,671			2,036			63,707
Total operating expenses	37,658			929			38,587			70,254			2,143			72,397
Loss from operations	(11,679		)	(1,102		)	(12,781		)	(22,321		)	(1,058		)	(23,379		)
Other income, net	334			4			338			717			—			717
Net loss	(12,206		)	(1,098		)	(13,304		)	(23,323		)	(1,058		)	(24,381		)
Net loss per common share, basic and diluted	(0.51		)	(0.05		)	(0.56		)	(0.99		)	(0.04		)	(1.03		)



	Three months ended March 31, 2018
	As Reported			Adjustment			As Revised
Revenue	$	30,565		$	1,197		$	31,762
Cost of revenue	8,611			(61		)	8,550
Gross profit	21,954			1,258			23,212
Research and development	4,019			24			4,043
Selling, general and administrative	28,577			1,190			29,767
Total operating expenses	32,596			1,214			33,810
Loss from operations	(10,642		)	44			(10,598		)
Other income, net	383			(4		)	379
Net loss	(11,117		)	40			(11,077		)



	Year ended December 31, 2017
	As Reported			Adjustment			As Revised
Revenue	$	98,509		$	620		$	99,129
Cost of revenue	27,708			495			28,203
Gross profit	70,801			125			70,926
Research and development	13,335			(70		)	13,265
Selling, general and administrative	84,737			515			85,252
Total operating expenses	98,072			445			98,517
Loss from operations	(27,271		)	(320		)	(27,591		)
Net loss	(29,420		)	(320		)	(29,740		)
Net loss per common share, basic and diluted	(1.30		)	(0.01		)	(1.31		)

Revised Consolidated Statements of Comprehensive Income (Loss)



	Three months ended June 30, 2019								Six months ended June 30, 2019
	As Reported			Adjustment		As Revised			As Reported			Adjustment		As Revised
Net loss	$	(11,467	)	$	742	$	(10,725	)	$	(19,486	)	$	511	$	(18,975	)
Comprehensive loss	(11,434		)	742		(10,692		)	(19,410		)	511		(18,899		)



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Net loss	$	(8,019	)	$	(231	)	$	(8,250	)
Comprehensive loss	(7,976		)	(231		)	(8,207		)



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Net loss	$	(48,280	)	$	(2,098	)	$	(50,378	)
Net change in unrealized gains on available-for-sale securities	24			25			49
Comprehensive loss	(48,256		)	(2,073		)	(50,329		)



	Three months ended September 30, 2018								Nine months ended September 30, 2018
	As Reported			Adjustment		As Revised			As Reported			Adjustment			As Revised
Net loss	$	(10,244	)	$	517	$	(9,727	)	$	(33,567	)	$	(541	)	$	(34,108	)
Net change in unrealized losses on available-for-sale securities	19			—		19			(83		)	129			46
Foreign currency translation	(10		)	10		—			(10		)	10			—
Comprehensive loss	(10,235		)	527		(9,708		)	(33,660		)	(402		)	(34,062		)



	Three months ended June 30, 2018									Six months ended June 30, 2018
	As Reported			Adjustment			As Revised			As Reported			Adjustment			As Revised
Net loss	$	(12,206	)	$	(1,098	)	$	(13,304	)	$	(23,323	)	$	(1,058	)	$	(24,381	)
Comprehensive loss	(12,159		)	(1,098		)	(13,257		)	(23,296		)	(1,058		)	(24,354		)



	Three months ended March 31, 2018
	As Reported			Adjustment		As Revised
Net loss	$	(11,117	)	$	40	$	(11,077	)
Comprehensive loss	(11,137		)	40		(11,097		)



	Year ended December 31, 2017
	As Reported			Adjustment			As Revised
Net loss	$	(29,420	)	$	(320	)	$	(29,740	)
Comprehensive loss	(29,476		)	(320		)	(29,796		)

Revised Consolidated Statements of Cash Flows



	Six months ended June 30, 2019
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(19,486	)	$	511		$	(18,975	)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,292			18			1,310
Stock-based compensation	11,745			(82		)	11,663
Provision for doubtful accounts and contractual allowances	10,683			1,687			12,370
Amortization of operating lease right-of-use assets	5,061			83			5,144
Changes in operating assets and liabilities:
Accounts receivable	(17,844		)	(1,570		)	(19,414		)
Prepaid expenses and other current assets	(27		)	263			236
Other assets	(1,174		)	18			(1,156		)
Accounts payable	1,025			(6		)	1,019
Accrued liabilities	(3,187		)	(70		)	(3,257		)
Deferred revenue	(45		)	(98		)	(143		)
Operating lease liabilities	(3,724		)	(114		)	(3,838		)
Net cash used in operating activities	(16,781		)	639			(16,142		)
Cash flows from investing activities
Purchases of property and equipment	(4,468		)	(809		)	(5,277		)
Net cash provided by investing activities	11,106			(809		)	10,297
Net increase in cash, cash equivalents, and restricted cash	(3,869		)	(170		)	(4,039		)
Cash, cash equivalents and restricted cash end of period	16,154			(170		)	15,984
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	284			16			300



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(8,019	)	$	(231	)	$	(8,250	)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	4,415			441			4,856
Provision for doubtful accounts and contractual allowances	4,709			702			5,411
Changes in operating assets and liabilities:
Accounts receivable	(10,984		)	(1,408		)	(12,392		)
Prepaid expenses and other current assets	(169		)	140			(29		)
Accrued liabilities	(6,380		)	319			(6,061		)
Deferred revenue	66			(27		)	39
Net cash used in operating activities	(17,099		)	(64		)	(17,163		)
Cash flows from investing activities
Purchases of property and equipment	(1,635		)	(70		)	(1,705		)
Net cash provided by investing activities	26,449			(70		)	26,379
Net increase in cash, cash equivalents, and restricted cash	8,212			(134		)	8,078
Cash and cash equivalents end of period	28,235			(134		)	28,101



	Year ended December 31, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(48,280	)	$	(2,098	)	$	(50,378	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	15,218			1,230			16,448
Changes in operating assets and liabilities:
Accounts receivable	(22,885		)	1,138			(21,747		)
Accrued liabilities	10,776			(275		)	10,501
Deferred revenue	5			(20		)	(15		)
Net cash used in operating activities	(29,068		)	(25		)	(29,093		)
Cash flows from investing activities
Purchases of available-for-sale investments	(93,158		)	25			(93,133		)
Net cash provided by investing activities	34,117			25			34,142



	Nine months ended September 30, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(33,567	)	$	(541	)	$	(34,108	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	8,921			671			9,592
Changes in operating assets and liabilities:
Accounts receivable	(15,088		)	10			(15,078		)
Accrued liabilities	3,335			(125		)	3,210
Deferred revenue	(64		)	(15		)	(79		)



	Six months ended June 30, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(23,323	)	$	(1,058	)	$	(24,381	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	6,440			1,245			7,685
Changes in operating assets and liabilities:
Accrued liabilities	497			(186		)	311
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	218			34			252



	Three months ended March 31, 2018
	As Reported			Adjustment			As Revised
Cash flows from operating activities
Net loss	$	(11,117	)	$	40		$	(11,077	)
Adjustments to reconcile net loss to net cash used in operating activities:
Provision for doubtful accounts and contractual allowances	2,680			206			2,886
Changes in operating assets and liabilities:
Accrued liabilities	(2,977		)	(246		)	(3,223		)



	Year ended December 31, 2017
	As Reported		Adjustment		As Revised
Cash flows from operating activities
Net loss	(29,420	)	(320	)	(29,740	)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	10,123		(371	)	9,752
Provision for doubtful accounts and contractual allowances	9,403		(181	)	9,222
Changes in operating assets and liabilities:
Accounts receivable	(12,950	)	479		(12,471	)
Accrued liabilities	5,364		393		5,757
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities	35		75		110

Revised Consolidated Statements of Shareholder's Equity



	Six months ended June 30, 2019
	As Reported			Adjustment			As Revised
Stock-based compensation expense	$	11,745		$	(82	)	$	11,663
Additional-paid-in-capital ending balance	271,551			(82		)	271,469
Accumulated other comprehensive loss beginning balance	(41		)	25			(16		)
Accumulated other comprehensive loss ending balance	35			25			60
Accumulated deficit beginning balance	(203,515		)	(2,310		)	(205,825		)
Net loss	(19,486		)	511			(18,975		)
Accumulated deficit ending balance	(223,001		)	(1,799		)	(224,800		)
Total stockholders' equity	48,608			(1,856		)	46,752



	Three months ended March 31, 2019
	As Reported			Adjustment			As Revised
Stock-based compensation expense	$	4,415		$	441		$	4,856
Additional-paid-in-capital ending balance	261,231			441			261,672
Accumulated other comprehensive loss beginning balance	(41		)	25			(16		)
Accumulated other comprehensive loss ending balance	2			25			27
Accumulated deficit beginning balance	(203,515		)	(2,310		)	(205,825		)
Net loss	(8,019		)	(231		)	(8,250		)
Accumulated deficit ending balance	(211,534		)	(2,541		)	(214,075		)
Total stockholders' equity	49,723			(2,075		)	47,648



	Year Ended December 31, 2018
	As Reported			Adjustment			As Revised
Unrealized loss on investments	$	24		$	25		$	49
Accumulated other comprehensive loss ending balance	(41		)	25			(16		)
Accumulated deficit beginning balance	(156,589		)	(212		)	(156,801		)
Net loss	(48,280		)	(2,098		)	(50,378		)
Accumulated deficit ending balance	(203,515		)	(2,310		)	(205,825		)
Total stockholders' equity	54,422			(2,285		)	52,137



	Six Months Ended June 30, 2018
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(156,589	)	$	(212	)	$	(156,801	)
Net loss	(23,323		)	(1,058		)	(24,381		)
Accumulated deficit ending balance	(178,558		)	(1,270		)	(179,828		)
Total stockholders' equity	68,466			(1,270		)	67,196



	Three Months Ended March 31, 2018
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(156,589	)	$	(212	)	$	(156,801	)
Net loss	(11,117		)	40			(11,077		)
Accumulated deficit ending balance	(166,352		)	(172		)	(166,524		)
Total stockholders' equity	72,623			(172		)	72,451



	Year Ended December 31, 2017
	As Reported			Adjustment			As Revised
Accumulated deficit beginning balance	$	(127,169	)	$	108		$	(127,061	)
Net loss	(29,420		)	(320		)	(29,740		)
Accumulated deficit ending balance	(156,589		)	(212		)	(156,801		)
Total stockholders' equity	79,553			(212		)	79,341

Organization and Description of Business Organization and Description of Business (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 10, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Net loss		$ (18,293)	$ (10,725)	$ (8,250)	$ (9,727)	$ (13,304)	$ (11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Common stock, shares issued (in shares)	1,575,342
Common stock, par value (in USD per share)		$ 0.001								$ 0.001		$ 0.001
Shares issued, price per share (in USD per share)	$ 73.00
Underwriters' option to purchase additional shares of common stock	205,479
Proceeds from issuance of common stock, net	$ 107,300									$ 6,409	$ 6,684

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Summary of Significant Accounting Policies - Schedule of Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Change In The Allowance For Doubtful Accounts
Balance, beginning of period	$ 7,296	$ 4,486
Add: provision for doubtful accounts	6,473	7,353
Less: write-offs, net of recoveries and other adjustments	(6,439)	(4,543)
Balance, end of period	$ 7,330	$ 7,296

Summary of Significant Accounting Policies - Disaggregated Revenue by Payor Type and Major Service (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue, net	$ 54,673	$ 52,441	$ 48,334	$ 38,441	$ 35,292	$ 31,762	$ 100,775	$ 67,054	$ 155,448	$ 105,495	$ 147,277	$ 99,129
Commercial Payors
Disaggregation of Revenue [Line Items]
Revenue, net	25,961			14,887					72,040	38,270
Non-contracted third-party payors
Disaggregation of Revenue [Line Items]
Revenue, net	2,686			3,126					9,016	10,302
Centers for Medicare & Medicaid
Disaggregation of Revenue [Line Items]
Revenue, net	15,379			10,952					42,573	29,317
Healthcare Institutions
Disaggregation of Revenue [Line Items]
Revenue, net	$ 10,647			$ 9,476					$ 31,819	$ 27,606

Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2019 USD ($) embedded_leases_with_suppliers	Sep. 30, 2018 USD ($)	Dec. 31, 2018	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Oct. 04, 2018 ft²
Summary Of Significant Accounting Policies [Line Items]
Total revenue recognized that was included in contract liability		$ 1,200,000	$ 1,200,000
Number of embedded leases with suppliers \| embedded_leases_with_suppliers		0
Operating lease right-of-use assets		$ 91,935,000			$ 94,243,000	$ 8,962,000
Operating lease liabilities		$ 95,135,000
Accounting Standards Codification 606 cumulative effect adjustment upon adoption							$ 0
Topic 842
Summary Of Significant Accounting Policies [Line Items]
Operating lease right-of-use assets							10,200,000
Operating lease liabilities							$ 10,000,000.0
Office lease \| San Francisco
Summary Of Significant Accounting Policies [Line Items]
Lease rentable area (in square feet) \| ft²								117,560
Zio XT service
Summary Of Significant Accounting Policies [Line Items]
Period from device applied to the time the report is posted (in days)		20 days
Maximum \| Zio XT service
Summary Of Significant Accounting Policies [Line Items]
Equipment wear period (in days)		14 days
Revenue \| Customer Concentration Risk \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (in percentage)	38.00%	36.00%	37.00%	33.00%
Accounts Receivable \| Accounts Receivable Concentration Risk \| Federal Government Agencies
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (in percentage)		21.00%		17.00%

Cash Equivalents and Investments - Schedule of Cash Equivalents and Available For Sale Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 159,078	$ 73,427
Gains	40	3
Losses	(1)	(19)
Estimated Fair Value	159,117	73,411
Cash equivalents	32,000	15,091
Short-term investments	118,091	58,320
Long-term investments	9,026	0
Total cash equivalents and available-for-sale investments	159,117	73,411
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	85,435	9,976
Gains	34
Losses		(1)
Estimated Fair Value	85,469	9,975
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,017	16,514
Gains	6	3
Losses	(1)	(18)
Estimated Fair Value	15,022	16,499
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	34,592	36,331
Estimated Fair Value	34,592	36,331
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	24,034	10,606
Estimated Fair Value	$ 24,034	$ 10,606

Cash Equivalents and Investments - Schedule of Fair Value of Short-term and Long-term Marketable Securities Classified by Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Cash Equivalents And Investments [Abstract]
Due within one year	$ 150,091	$ 73,411
Due after one year through three years	9,026	0
Estimated Fair Value	$ 159,117	$ 73,411

Cash Equivalents and Investments - Schedule of Available-for-Sale Securities Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fair Value (less than 12 months)	$ 17,498
Unrealized Loss (less than 12 months)	(11)
Fair Value (12 months or Greater)	2,993
Unrealized Loss (12 months or Greater)	(8)
Fair Value	20,491
Unrealized Loss	(19)
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Fair Value (less than 12 months)	5,977
Unrealized Loss (less than 12 months)	(1)
Fair Value (12 months or Greater)	0
Unrealized Loss (12 months or Greater)	0
Fair Value	5,977
Unrealized Loss	(1)
Corporate notes
Debt Securities, Available-for-sale [Line Items]
Fair Value (less than 12 months)	11,521
Unrealized Loss (less than 12 months)	(10)
Fair Value (12 months or Greater)	2,993
Unrealized Loss (12 months or Greater)	(8)
Fair Value	14,514
Unrealized Loss	$ (18)

Fair Value Measurements - Schedule of Fair Value of Company's Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 159,117	$ 73,411
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	24,034	10,606
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	135,083	62,805
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	24,034	10,606
Money market funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	24,034	10,606
Money market funds \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Money market funds \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	85,469	9,975
U.S. government securities \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
U.S. government securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	85,469	9,975
U.S. government securities \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Corporate notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	15,022	16,499
Corporate notes \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Corporate notes \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	15,022	16,499
Corporate notes \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	34,592	36,331
Commercial paper \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	0	0
Commercial paper \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	34,592	36,331
Commercial paper \| Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets	$ 0	$ 0

Balance Sheet Components - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Inventory [Line Items]
Inventory	$ 3,499			$ 3,499		$ 2,062
Other assets	5,574		$ 4,497	5,574		3,208
Depreciation and amortization	900	$ 600	$ 1,310	2,257	$ 1,673
Printed circuit board assemblies
Inventory [Line Items]
Other assets	$ 4,900			$ 4,900		$ 2,500

Balance Sheet Components - Components of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 24,518			$ 14,388
Less: accumulated depreciation and amortization	(6,715)			(5,230)
Total property and equipment, net	17,803	$ 13,444	$ 10,278	9,158	$ 7,594	$ 6,296
Laboratory and manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,050			2,750
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	1,062			1,062
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	724			925
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,921			726
Internal-use software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 13,761			$ 8,925

Balance Sheet Components - Components of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued vacation	$ 3,571			$ 2,825
Accrued payroll and related expenses	14,107			18,188
Accrued ESPP contribution	1,656			373
Accrued professional services fees	820			1,249
Claims payable	2,991			2,374
Cash paid for upfront fee	5,000			0
Other	4,082			1,679
Total accrued liabilities	$ 32,227	$ 23,362	$ 20,536	$ 26,688	$ 19,447	$ 16,595	$ 12,805	$ 16,112

Commitments and Contingencies - Narrative (Details)			9 Months Ended
Commitments and Contingencies - Narrative (Details)	Sep. 03, 2019 USD ($)	Oct. 04, 2018 USD ($) ft²	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease cost			$ 8,100,000
Cash paid for operating leases			$ 4,900,000
Number of options to extend lease		1
Weighted average remaining lease term			11 years 9 months 18 days
Weighted average discount rate (in percentage)			7.35%
Cash paid for upfront fee			$ 5,000,000	$ 0
Office lease \| San Francisco
Lessee, Lease, Description [Line Items]
Lease rentable area (in square feet) \| ft²		117,560
Renewal term of lease		5 years
Office lease \| San Francisco \| Standby letter of credit
Lessee, Lease, Description [Line Items]
Line of credit borrowing capacity		$ 6,900,000
Office lease \| San Francisco \| Maximum [Member]
Lessee, Lease, Description [Line Items]
Tenant improvement allowance		$ 2,400,000
Verily Life Sciences LLC
Lessee, Lease, Description [Line Items]
Cash paid for upfront fee			$ 5,000,000.0
Additional milestone payments, due in next 24 months	$ 12,750,000
Remaining term of agreement	24 months

Commitments and Contingencies - Schedule of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Maturities of Operating Lease Liabilities
2019 (remainder of year)	$ 1,558
2020	11,766
2021	11,680
2022	11,357
2023	11,696
Thereafter	98,818
Total payments due	146,875
Less: imputed interest	(51,740)
Total lease liabilities	$ 95,135

Commitments and Contingencies - Schedule of Minimum Future Lease Payments under Previous Lease Accounting Standard (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Maturities of Operating Lease Liabilities
2019	$ 8,135
2020	10,669
2021	10,828
2022	11,150
2023	11,483
Thereafter	98,209
Total	$ 150,474

Debt - Narrative (Details)		1 Months Ended
Debt - Narrative (Details)	Oct. 23, 2018 USD ($)	Oct. 31, 2018 USD ($)	May 31, 2018 USD ($)	Dec. 31, 2015 USD ($) tranch	Nov. 30, 2012 USD ($) shares	Sep. 30, 2019 USD ($)	Aug. 31, 2016 USD ($)	Dec. 04, 2015 USD ($)
Pharmakon loan agreement
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 55,000,000.0
Number of tranches for loans \| tranch				2
Loss on extinguishment of debt	$ 3,000,000.0
Prepayment premium fee	1,000,000.0
Additional consideration for prepayment of debt	1,500,000
Repayment of debt		$ 35,800,000
Pharmakon loan agreement \| Silicon Valley Bank
Debt Instrument [Line Items]
Repayment of debt				$ 4,900,000
Pharmakon loan agreement \| Tranche A loans
Debt Instrument [Line Items]
Maximum borrowing capacity								$ 30,000,000.0
Fixed interest rate (in percentage)				9.50%
Interest due and payable (in percentage)				50.00%
Repayment of debt	30,000,000.0
Payment of accrued interest on debt	$ 3,300,000
Pharmakon loan agreement \| Tranche B loans
Debt Instrument [Line Items]
Maximum borrowing capacity		25,000,000.0
SVB loan agreement
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 15,000,000.0
SVB loan agreement \| Maximum
Debt Instrument [Line Items]
Eligible accounts receivable for borrowings (in percentage)				80.00%
SVB loan agreement \| Prime rate
Debt Instrument [Line Items]
Debt instrument interest rate spread (in percentage)				0.25%
SVB loan agreement \| Standby letters of credit
Debt Instrument [Line Items]
Line of credit							$ 3,100,000
Third amended and restated SVB loan agreement \| Standby letters of credit
Debt Instrument [Line Items]
Maximum borrowing capacity		11,000,000.0
Proceeds from line of credit		6,900,000
Third amended and restated SVB loan agreement \| SVB term loan
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 35,000,000.0
Number of monthly payments of principal and interest		36 months
Third amended and restated SVB loan agreement \| SVB term loan \| Minimum
Debt Instrument [Line Items]
Interest rate (in percentage)		4.25%
Third amended and restated SVB loan agreement \| SVB term loan \| Prime rate
Debt Instrument [Line Items]
Basis spread deduction on variable rate (in percentage)		0.75%
Third amended and restated SVB loan agreement \| Revolving credit facility
Debt Instrument [Line Items]
Line of credit						$ 0
Third amended and restated SVB loan agreement \| Revolving credit facility \| Minimum
Debt Instrument [Line Items]
Interest rate (in percentage)		5.00%
Third amended and restated SVB loan agreement \| Revolving credit facility \| Maximum
Debt Instrument [Line Items]
Eligible accounts receivable for borrowings (in percentage)		75.00%
CHCF note
Debt Instrument [Line Items]
Repayment of debt			$ 1,500,000
Payment of accrued interest on debt			$ 200,000
Proceeds from long-term debt, net of issuance costs					$ 1,500,000
Debt instrument accrues simple interest rate (in percentage)					2.00%
CHCF note \| Series D convertible preferred stock
Debt Instrument [Line Items]
Warrants issued to purchase shares (in shares) \| shares					22,807

Stockholders' Equity - Narrative (Details) - USD ($)	9 Months Ended
Stockholders' Equity - Narrative (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Equity [Abstract]
Common stock, shares authorized	100,000,000	100,000,000
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, par value (in USD per share)	$ 0.001	$ 0.001
Dividends declared	$ 0

Equity Incentive Plans - Summary of Share-based Awards Available for Grant under 2016 Plan (Details) - 2016 Plan - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Share-Based Awards Available For Grant
Beginning balance	4,717,292	4,034,152
Additional awards authorized	1,218,402	1,168,865
Awards granted	(620,624)	(666,913)
Awards forfeited	155,253	124,478
Awards withheld for tax purposes	58,341	56,710
Ending balance	5,528,664	4,717,292

Equity Incentive Plans - Summary of Stock Option Activity Under 2006 and 2016 Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Options Outstanding
Beginning balance	2,094,137	2,601,181
Options granted	20,010	366,928
Options exercised	(426,655)	(798,424)
Options forfeited	(61,865)	(75,548)
Ending balance	1,625,627	2,094,137	2,601,181
Options exercisable	1,191,485
Options vested and expected to vest	1,605,077
Weighted- Average Exercise Price Per Share
Beginning Balance (in USD per share)	$ 23.20	$ 12.24
Options granted (in USD per share)	82.77	68.32
Options exercised (in USD per share)	9.98	7.19
Options forfeited (in USD per share)	53.96	34.30
Ending Balance (in USD per share)	26.23	$ 23.20	$ 12.24
Options exercisable (in USD per share)	17.54
Options vested and expected to vest (in USD per share)	$ 25.82
Weighted- Average Remaining Contractual Life (years)
Beginning Balance	6 years 4 months 13 days	7 years 7 days	7 years 2 months 1 day
Ending Balance	6 years 4 months 13 days	7 years 7 days	7 years 2 months 1 day
Options exercisable	5 years 9 months 25 days
Options vested and expected to vest	6 years 4 months 6 days
Aggregate Intrinsic Value (in thousands)
Beginning Balance (in USD)	$ 97,976	$ 113,958
Ending Balance (in USD)	78,664	$ 97,976	$ 113,958
Options exercisable (in USD)	67,568
Options vested and expected to vest (in USD)	$ 78,284

Equity Incentive Plans - Narrative (Details) - $ / shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of options (in USD per share)	$ 38.29	$ 32.23
Unvested restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock units granted (in shares)	600,614
Restricted stock units vested (in shares)	115,260
Restricted stock units forfeited (in shares)	151,729

Stock-Based Compensation - Schedule of Fair Value of Employee and Director Stock Options Estimated Using Weighted Average Assumptions (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement [Abstract]
Expected term (in years)	0 years	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility	0.00%	44.70%	45.00%	45.80%
Risk-free interest rate	0.00%	2.85%	2.39%	2.74%
Dividend yield	0.00%	0.00%	0.00%	0.00%

Stock-Based Compensation - Summary of Total Stock-Based Compensation Expense Included in Statements of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 7,401	$ 4,211	$ 19,064	$ 11,534
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	0	86	225	224
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	1,242	801	3,366	2,158
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 6,159	$ 3,324	$ 15,473	$ 9,152

Stock-Based Compensation - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Feb. 28, 2019	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to unvested stock options		$ 10.3
Unamortized compensation costs related to unvested stock options, expected period of recognition		1 year 10 months 24 days
Restricted Stock Units ("RSUs")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unamortized compensation costs related to unvested stock options, expected period of recognition		2 years 6 months
Total unamortized compensation costs, net of estimated forfeitures related to restricted stock unit		$ 47.9
Performance Based Restricted Stock Units ("PRSU")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2 years
Cumulative expenses		$ 3.3
Performance Based Restricted Stock Units ("PRSU") \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance threshold (in percentage)	75.00%
Performance target to be earned at performance threshold (in percentage)	50.00%
Performance Based Restricted Stock Units ("PRSU") \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance threshold (in percentage)	125.00%	134.00%
Performance target to be earned at performance threshold (in percentage)	200.00%
Fair value of shares granted (up to)	$ 18.5
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to unvested stock options		$ 1.4
Unamortized compensation costs related to unvested stock options, expected period of recognition		8 months 12 days

Net Loss Per Common Share - Computation of Basic and Diluted Net Loss per Share Attributable to Common Stock holders (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Numerator:
Net loss	$ (18,293)	$ (10,725)	$ (8,250)	$ (9,727)	$ (13,304)	$ (11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Denominator:
Weighted-average shares used to compute net loss per common share, basic and diluted	25,247,831			24,059,010					24,818,482	23,764,153
Net loss per common share, basic and diluted	$ (0.72)	$ (0.43)	$ (0.34)	$ (0.40)	$ (0.56)		$ (0.77)	$ (1.03)	$ (1.50)	$ (1.44)	$ (2.11)	$ (1.31)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Net Loss Per Common Share - Schedule of Anti-dilutive Securities Excluded from Diluted Net Loss per Common Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	2,509,149	2,815,968
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	1,625,627	2,205,126
PRSUs and RSUs issued and unvested
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	881,516	605,985
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	2,006	4,857

Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 34,634	$ 15,984	$ 28,101	$ 20,023
Accounts receivable, net	25,003	26,693	26,771	19,790	$ 19,975	$ 18,001	$ 17,140	$ 13,134
Prepaid expenses and other current assets	3,653	3,528	3,670	4,100
Total current assets	184,880	92,219	91,553	104,295	106,241	108,592	111,517	119,762
Property and equipment, net	17,803	13,444	10,278	9,158		7,594		6,296
Operating lease right-of-use assets	91,935	94,243	8,962
Other assets	5,574	4,497		3,208
Total assets	310,080	205,265	115,229	117,523	118,499	119,888	122,296	133,379
Current liabilities:
Accrued liabilities	32,227	23,362	20,536	26,688	19,447	16,595	12,805	16,112
Deferred revenue	889	1,081	1,262	1,223	1,159
Operating lease liabilities, current portion	8,036	7,160	4,841
Total current liabilities	45,467	35,370	28,728	30,334	22,517	19,895	17,085	21,386
Operating lease liabilities, noncurrent portion	87,099	88,216	3,931
Total liabilities	167,495	158,513	67,581	65,386	55,285	52,692	49,845	54,038
Additional paid-in capital	385,614	271,469	261,672	257,955
Accumulated other comprehensive income	39	60	27	(16)	(19)
Accumulated deficit	(243,093)	(224,800)	(214,075)	(205,825)	(189,555)	(179,828)	(166,524)	(156,801)
Total stockholders’ equity	142,585	46,752	47,648	52,137	63,214	67,196	72,451	79,341
Total liabilities and stockholders’ equity	$ 310,080	205,265	115,229	117,523	118,499	119,888	122,296	133,379
As Reported
Assets
Cash and cash equivalents		16,154	28,235
Accounts receivable, net		29,137	28,252	21,977	20,465	19,065	17,165	12,953
Prepaid expenses and other current assets		3,669	3,810
Total current assets		94,974	93,308	106,482	106,731	109,656	111,542	119,581
Property and equipment, net		12,618	10,208			7,560		6,221
Operating lease right-of-use assets		94,326	9,232
Other assets		4,515
Total assets		207,295	117,184	119,710	118,989	120,918	122,321	133,123
Current liabilities:
Accrued liabilities		23,304	20,099	26,570	19,178	16,355	12,658	15,644
Deferred revenue		1,199	1,309	1,243	1,174
Operating lease liabilities, current portion		7,384	5,052
Total current liabilities		35,654	28,549	30,236	22,263	19,655	16,938	20,918
Operating lease liabilities, noncurrent portion		88,106	3,990
Total liabilities		158,687	67,461	65,288	55,031	52,452	49,698	53,570
Additional paid-in capital		271,551	261,231
Accumulated other comprehensive income		35	2	(41)	(29)
Accumulated deficit		(223,001)	(211,534)	(203,515)	(188,801)	(178,558)	(166,352)	(156,589)
Total stockholders’ equity		48,608	49,723	54,422	63,958	68,466	72,623	79,553
Total liabilities and stockholders’ equity		207,295	117,184	119,710	118,989	120,918	122,321	133,123
Adjustment
Assets
Cash and cash equivalents		(170)	(134)
Accounts receivable, net		(2,444)	(1,481)	(2,187)	(490)	(1,064)	(25)	181
Prepaid expenses and other current assets		(141)	(140)
Total current assets		(2,755)	(1,755)	(2,187)	(490)	(1,064)	(25)	181
Property and equipment, net		826	70			34		75
Operating lease right-of-use assets		(83)	(270)
Other assets		(18)
Total assets		(2,030)	(1,955)	(2,187)	(490)	(1,030)	(25)	256
Current liabilities:
Accrued liabilities		58	437	118	269	240	147	468
Deferred revenue		(118)	(47)	(20)	(15)
Operating lease liabilities, current portion		(224)	(211)
Total current liabilities		(284)	179	98	254	240	147	468
Operating lease liabilities, noncurrent portion		110	(59)
Total liabilities		(174)	120	98	254	240	147	468
Additional paid-in capital		(82)	441
Accumulated other comprehensive income		25	25	25	10
Accumulated deficit		(1,799)	(2,541)	(2,310)	(754)	(1,270)	(172)	(212)
Total stockholders’ equity		(1,856)	(2,075)	(2,285)	(744)	(1,270)	(172)	(212)
Total liabilities and stockholders’ equity		$ (2,030)	$ (1,955)	$ (2,187)	$ (490)	$ (1,030)	$ (25)	$ 256

Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Statements of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue	$ 54,673	$ 52,441	$ 48,334	$ 38,441	$ 35,292	$ 31,762	$ 100,775	$ 67,054	$ 155,448	$ 105,495	$ 147,277	$ 99,129
Cost of revenue	13,785	13,012	11,773	9,953	9,486	8,550	24,785	18,036	38,570	27,989	38,795	28,203
Gross profit	40,888	39,429	36,561	28,488	25,806	23,212	75,990	49,018	116,878	77,506	108,482	70,926
Research and development	13,499	7,833	6,699	5,086	4,647	4,043	14,532	8,690	28,031	13,776	20,860	13,265
Selling, general and administrative	45,649	42,161	38,066	32,623	33,940	29,767	80,227	63,707	125,876	96,330	133,313	85,252
Total operating expenses	59,148	49,994	44,765	37,709	38,587	33,810	94,759	72,397	153,907	110,106	154,173	98,517
Loss from operations	(18,260)	(10,565)	(8,204)	(9,221)	(12,781)	(10,598)	(18,769)	(23,379)	(37,029)	(32,600)	(45,691)	(27,591)
Other income, net	396	295	375	355	338	379	670	717	1,066	1,072	1,501
Loss before income taxes	(18,273)	(10,710)	(8,238)	(9,727)			(18,948)		(37,221)	(34,108)	(50,334)
Net loss	$ (18,293)	$ (10,725)	$ (8,250)	$ (9,727)	$ (13,304)	(11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Net loss per common share, basic and diluted	$ (0.72)	$ (0.43)	$ (0.34)	$ (0.40)	$ (0.56)		$ (0.77)	$ (1.03)	$ (1.50)	$ (1.44)	$ (2.11)	$ (1.31)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		$ 53,331	$ 47,214	$ 38,104	$ 35,469	30,565	$ 100,545	$ 66,034		$ 104,138	$ 147,293	$ 98,509
Cost of revenue		12,825	11,730	9,949	9,490	8,611	24,555	18,101		28,050	38,579	27,708
Gross profit		40,506	35,484	28,155	25,979	21,954	75,990	47,933		76,088	108,714	70,801
Research and development		8,639	6,756	5,164	4,564	4,019	15,395	8,583		13,747	20,750	13,335
Selling, general and administrative		43,189	36,705	32,739	33,094	28,577	79,894	61,671		94,410	131,582	84,737
Total operating expenses		51,828	43,461	37,903	37,658	32,596	95,289	70,254		108,157	152,332	98,072
Loss from operations		(11,322)	(7,977)	(9,748)	(11,679)	(10,642)	(19,299)	(22,321)		(32,069)	(43,618)	(27,271)
Other income, net		310	379	365	334	383	689	717		1,082	1,526
Loss before income taxes		(11,452)	(8,007)	(10,244)			(19,459)			(33,567)	(48,236)
Net loss		$ (11,467)	$ (8,019)	$ (10,244)	$ (12,206)	(11,117)	$ (19,486)	$ (23,323)		$ (33,567)	$ (48,280)	$ (29,420)
Net loss per common share, basic and diluted		$ (0.46)	$ (0.33)	$ (0.43)	$ (0.51)		$ (0.79)	$ (0.99)		$ (1.41)	$ (2.02)	$ (1.30)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Revenue		$ (890)	$ 1,120	$ 337	$ (177)	1,197	$ 230	$ 1,020		$ 1,357	$ (16)	$ 620
Cost of revenue		187	43	4	(4)	(61)	230	(65)		(61)	216	495
Gross profit		(1,077)	1,077	333	(173)	1,258	0	1,085		1,418	(232)	125
Research and development		(806)	(57)	(78)	83	24	(863)	107		29	110	(70)
Selling, general and administrative		(1,028)	1,361	(116)	846	1,190	333	2,036		1,920	1,731	515
Total operating expenses		(1,834)	1,304	(194)	929	1,214	(530)	2,143		1,949	1,841	445
Loss from operations		757	(227)	527	(1,102)	44	530	(1,058)		(531)	(2,073)	(320)
Other income, net		(15)	(4)	(10)	4	(4)	(19)	0		(10)	(25)
Loss before income taxes		742	(231)	517			511			(541)	(2,098)
Net loss		$ 742	$ (231)	$ 517	$ (1,098)	$ 40	$ 511	$ (1,058)		$ (541)	$ (2,098)	$ (320)
Net loss per common share, basic and diluted		$ 0.03	$ (0.01)	$ 0.03	$ (0.05)		$ 0.02	$ (0.04)		$ (0.03)	$ (0.09)	$ (0.01)

Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Statements of Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss	$ (18,293)	$ (10,725)	$ (8,250)	$ (9,727)	$ (13,304)	$ (11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Net change in unrealized gain on investments	(21)	33	43	19	47	(20)			55	46	49
Foreign currency translation				0						0
Comprehensive loss	$ (18,314)	(10,692)	(8,207)	(9,708)	(13,257)	(11,097)	(18,899)	(24,354)	$ (37,213)	(34,062)	(50,329)	(29,796)
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss		(11,467)	(8,019)	(10,244)	(12,206)	(11,117)	(19,486)	(23,323)		(33,567)	(48,280)	(29,420)
Net change in unrealized gain on investments				19						(83)	24
Foreign currency translation				(10)						(10)
Comprehensive loss		(11,434)	(7,976)	(10,235)	(12,159)	(11,137)	(19,410)	(23,296)		(33,660)	(48,256)	(29,476)
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net loss		742	(231)	517	(1,098)	40	511	(1,058)		(541)	(2,098)	(320)
Net change in unrealized gain on investments				0						129	25
Foreign currency translation				10						10
Comprehensive loss		$ 742	$ (231)	$ 527	$ (1,098)	$ 40	$ 511	$ (1,058)		$ (402)	$ (2,073)	$ (320)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Cash flows from operating activities
Net loss		$ (8,250)		$ (11,077)	$ (18,975)	$ (24,381)	$ (37,268)	$ (34,108)	$ (50,378)	$ (29,740)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	$ 900		$ 600		1,310		2,257	1,673
Stock-based compensation		4,856			11,663		19,064	11,534		9,752
Provision for doubtful accounts and contractual allowances		5,411		2,886	12,370	7,685	17,581	9,592	16,448	9,222
Amortization of operating lease right-of-use assets					5,144		7,452
Accounts receivable		(12,392)			(19,414)		(22,795)	(15,078)	(21,747)	(12,471)
Prepaid expenses and other current assets		(29)			236		(12)	(231)
Other assets					(1,156)		(2,366)	319
Accounts payable					1,019		(119)	(524)
Accrued liabilities		(6,061)		(3,223)	(3,257)	311	5,635	3,210	10,501	5,757
Deferred revenue		39			(143)		(334)	(79)	(15)
Operating lease liabilities					(3,838)		(4,079)
Net cash used in operating activities		17,163			(16,142)		(17,003)	(24,720)	29,093
Cash flows from investing activities
Purchases of property and equipment		(1,705)			(5,277)		(8,640)	(3,687)
Purchases of available-for-sale investments									(93,133)
Net cash provided by investing activities		26,379			10,297		(76,766)	29,848	34,142
Net increase in cash, cash equivalents, and restricted cash		8,078			(4,039)		14,611	8,674
Cash, cash equivalents and restricted cash end of period	$ 34,634	28,101	$ 17,345		15,984		34,634	17,345	20,023	8,671
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities					300	252	$ 2,259	86	135	110
As Reported
Cash flows from operating activities
Net loss		(8,019)		(11,117)	(19,486)	(23,323)		(33,567)	(48,280)	(29,420)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					1,292
Stock-based compensation		4,415			11,745					10,123
Provision for doubtful accounts and contractual allowances		4,709		2,680	10,683	6,440		8,921	15,218	9,403
Amortization of operating lease right-of-use assets					5,061
Accounts receivable		(10,984)			(17,844)			(15,088)	(22,885)	(12,950)
Prepaid expenses and other current assets		(169)			(27)
Other assets					(1,174)
Accounts payable					1,025
Accrued liabilities		(6,380)		(2,977)	(3,187)	497		3,335	10,776	5,364
Deferred revenue		66			(45)			(64)	5
Operating lease liabilities					(3,724)
Net cash used in operating activities		17,099			(16,781)				29,068
Cash flows from investing activities
Purchases of property and equipment		(1,635)			(4,468)
Purchases of available-for-sale investments									(93,158)
Net cash provided by investing activities		26,449			11,106				34,117
Net increase in cash, cash equivalents, and restricted cash		8,212			(3,869)
Cash, cash equivalents and restricted cash end of period		28,235			16,154
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities					284	218			101	35
Adjustment
Cash flows from operating activities
Net loss		(231)		40	511	(1,058)		(541)	(2,098)	(320)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization					18
Stock-based compensation		441			(82)					(371)
Provision for doubtful accounts and contractual allowances		702		206	1,687	1,245		671	1,230	(181)
Amortization of operating lease right-of-use assets					83
Accounts receivable		(1,408)			(1,570)			(10)	1,138	479
Prepaid expenses and other current assets		140			263
Other assets					18
Accounts payable					(6)
Accrued liabilities		319		$ (246)	(70)	(186)		(125)	(275)	393
Deferred revenue		(27)			(98)			$ (15)	(20)
Operating lease liabilities					(114)
Net cash used in operating activities		64			639				25
Cash flows from investing activities
Purchases of property and equipment		(70)			(809)
Purchases of available-for-sale investments									25
Net cash provided by investing activities		(70)			(809)				25
Net increase in cash, cash equivalents, and restricted cash		(134)			(170)
Cash, cash equivalents and restricted cash end of period		$ (134)			(170)
Supplemental disclosures of cash flow information
Property, plant and equipment costs included in liabilities					$ 16	$ 34			$ 34	$ 75

Revision of Prior Period Financial Statements - Schedule of Revised Consolidated Statements of Shareholder's Equity (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense	$ 7,401	$ 6,807	$ 4,856	$ 4,211	$ 4,076	$ 3,247
Beginning balance	46,752	47,648	52,137	67,196	72,451	79,341	$ 52,137	$ 79,341	$ 52,137	$ 79,341	$ 79,341
Net change in unrealized gain on investments	(21)	33	43	19	47	(20)			55	46	49
Net loss	(18,293)	(10,725)	(8,250)	(9,727)	(13,304)	(11,077)	(18,975)	(24,381)	(37,268)	(34,108)	(50,378)	$ (29,740)
Ending balance	142,585	46,752	47,648	63,214	67,196	72,451	46,752	67,196	142,585	63,214	52,137	79,341
As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	48,608	49,723	54,422	68,466	72,623	79,553	54,422	79,553	54,422	79,553	79,553
Net change in unrealized gain on investments				19						(83)	24
Net loss		(11,467)	(8,019)	(10,244)	(12,206)	(11,117)	(19,486)	(23,323)		(33,567)	(48,280)	(29,420)
Ending balance		48,608	49,723	63,958	68,466	72,623	48,608	68,466		63,958	54,422	79,553
Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	(1,856)	(2,075)	(2,285)	(1,270)	(172)	(212)	(2,285)	(212)	(2,285)	(212)	(212)
Net change in unrealized gain on investments				0						129	25
Net loss		742	(231)	517	(1,098)	40	511	(1,058)		(541)	(2,098)	(320)
Ending balance		(1,856)	(2,075)	(744)	(1,270)	(172)	(1,856)	(1,270)		(744)	(2,285)	(212)
Additional Paid-In Capital
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense	7,401		4,856	4,211	4,076	3,247	11,663
Beginning balance	271,469	261,672	257,955	247,039	239,037	236,184	257,955	236,184	257,955	236,184	236,184
Net change in unrealized gain on investments	0	0	0	0	0	0
Net loss	0	0	0	0	0	0
Ending balance	385,614	271,469	261,672	252,765	247,039	239,037	271,469	247,039	385,614	252,765	257,955	236,184
Additional Paid-In Capital \| As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense			4,415				11,745
Beginning balance	271,551	261,231
Ending balance		271,551	261,231				271,551
Additional Paid-In Capital \| Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense			441				(82)
Beginning balance	(82)	441
Ending balance		(82)	441				(82)
Accumulated Other Comprehensive Income (Loss)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense	0	0	0	0	0	0
Beginning balance	60	27	(16)	(38)	(85)	(65)	(16)	(65)	(16)	(65)	(65)
Net change in unrealized gain on investments	(21)	33	43	19	47	(20)					49
Net loss	0	0	0	0	0	0
Ending balance	39	60	27	(19)	(38)	(85)	60	(38)	39	(19)	(16)	(65)
Accumulated Other Comprehensive Income (Loss) \| As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	35	2	(41)				(41)		(41)
Net change in unrealized gain on investments											24
Ending balance		35	2				35				(41)
Accumulated Other Comprehensive Income (Loss) \| Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	25	25	25				25		25
Net change in unrealized gain on investments											25
Ending balance		25	25				25				25
Accumulated deficit:
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Stock-based compensation expense	0	0	0	0	0	0
Beginning balance	(224,800)	(214,075)	(205,825)	(179,828)	(166,524)	(156,801)	(205,825)	(156,801)	(205,825)	(156,801)	(156,801)	(127,061)
Net change in unrealized gain on investments	0	0	0	0	0	0
Net loss	(18,293)	(10,725)	(8,250)	(9,727)	(13,304)	(11,077)	(18,975)	(24,381)			(50,378)	(29,740)
Ending balance	(243,093)	(224,800)	(214,075)	(189,555)	(179,828)	(166,524)	(224,800)	(179,828)	(243,093)	(189,555)	(205,825)	(156,801)
Accumulated deficit: \| As Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	(223,001)	(211,534)	(203,515)	(178,558)	(166,352)	(156,589)	(203,515)	(156,589)	(203,515)	(156,589)	(156,589)	(127,169)
Net loss			(8,019)			(11,117)	(19,486)	(23,323)			(48,280)	(29,420)
Ending balance		(223,001)	(211,534)		(178,558)	(166,352)	(223,001)	(178,558)			(203,515)	(156,589)
Accumulated deficit: \| Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning balance	$ (1,799)	(2,541)	(2,310)	$ (1,270)	(172)	(212)	(2,310)	(212)	$ (2,310)	$ (212)	(212)	108
Net loss			(231)			40	511	(1,058)			(2,098)	(320)
Ending balance		$ (1,799)	$ (2,541)		$ (1,270)	$ (172)	$ (1,799)	$ (1,270)			$ (2,310)	$ (212)

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company recorded a tax provision related to its U.K. entity during the three and nine months ended September 30, 2019. Due to the uncertainties surrounding the realization of the U.S. deferred tax assets through future taxable income, the Company has provided a full valuation allowance and, therefore, no benefit has been recognized for the U.S. net operating loss carryforwards and other deferred tax assets.

Subsequent events (Notes)	12 Months Ended
Subsequent events (Notes)	Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Events [Text Block]	Subsequent Events Agreement with Bristol-Meyers Squibb Company ("BMS") On November 12, 2019, the Company entered into a Master Services Agreement ("MSA") with Bristol-Meyers Squibb Company ("BMS") to provide services in connection with certain clinical studies BMS is conducting. Under the terms of the first Statement of Work ("SOW") attached to the MSA, the Company is responsible for key deliverables associated with the provision of the Zio XT monitor and customized services including reporting of key data elements. BMS will pay the Company fees up to a maximum of $6.8 million for services performed of the under the terms of the first Statement of Work attached to the MSA.

Cash Equivalents and Investments - Narrative (Details)	9 Months Ended
Cash Equivalents and Investments - Narrative (Details)	Sep. 30, 2019 Investment
Cash Equivalents And Investments [Abstract]
Available-for-sale securities, weighted average maturity of days	161 days
Number of unrealized loss position for more than 12 months in investments	0

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Carrying amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding interest-bearing obligations	$ 34.9	$ 34.9
Estimated fair value \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding interest-bearing obligations	$ 35.2	$ 34.9

Subsequent events (Details) $ in Millions	Nov. 12, 2019 USD ($)
Bristol-Meyers Squibb Company [Member] \| Maximum [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Unbilled Contracts Receivable	$ 6.8

Summary of Significant Accounting Policies - Schedule of Changes in Contractual Allowance (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Changes In The Contractual Allowance
Balance, beginning of period	$ 9,205	$ 6,345
Add: provision for contractual allowances	11,108	9,095
Less: realized contractual adjustments	(7,162)	(6,235)
Balance, end of period	$ 13,151	$ 9,205

Balance Sheet Components - Components of Inventory and Printed Circuit Board Assemblies ("PCBAs") (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory [Line Items]
Total inventory and printed circuit board assemblies	$ 3,499	$ 2,062
Raw materials
Inventory [Line Items]
Total inventory and printed circuit board assemblies	1,341	676
Finished goods
Inventory [Line Items]
Total inventory and printed circuit board assemblies	$ 2,158	$ 1,386

Stockholders' Equity - Schedule Of Common Stock Shares Reserved For Future Issuance (Details) - shares	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Shares available for future issuance	9,256,035	8,253,899
Common stock warrants issued and outstanding
Class of Stock [Line Items]
Shares available for future issuance	2,006	4,857
Options issued and outstanding
Class of Stock [Line Items]
Shares available for future issuance	1,625,627	2,094,137
Unvested restricted stock units
Class of Stock [Line Items]
Shares available for future issuance	881,516	547,891
Shares available for grant under future stock plans
Class of Stock [Line Items]
Shares available for future issuance	6,746,886	5,607,014

Label	Element	Value
Accounting Standards Update 2014-09 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,354,000
Accounting Standards Update 2014-09 [Member] \| Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 1,354,000