iRhythm (IRTC) 10-Q 2 May 24 2024 Q1 Quarterly report Financial data

Cover Page

Cover Page - shares	3 Months Ended
	Mar. 31, 2024	Apr. 25, 2024
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
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
Title of 12(b) Security	Common Stock, Par Value $0.001 Per Share
Trading Symbol	IRTC
Security Exchange Name	NASDAQ
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		31,104,883
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Entity Central Index Key	0001388658
Current Fiscal Year End Date	--12-31

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 520,421	$ 36,173
Marketable securities	48,671	97,591
Accounts receivable, net	89,712	61,484
Inventory	14,873	13,973
Prepaid expenses and other current assets	13,778	21,591
Total current assets	687,455	230,812
Property and equipment, net	112,274	104,114
Operating lease right-of-use assets	48,073	49,317
Restricted cash, long-term	8,358	0
Goodwill	862	862
Other assets	52,733	48,039
Total assets	909,755	433,144
Current liabilities:
Accounts payable	8,440	5,543
Accrued liabilities	70,044	83,362
Deferred revenue	3,068	3,306
Operating lease liabilities, current portion	15,289	15,159
Total current liabilities	96,841	107,370
Long-term senior convertible notes	644,076	0
Debt, noncurrent portion	0	34,950
Other noncurrent liabilities	908	1,012
Operating lease liabilities, noncurrent portion	77,640	79,715
Total liabilities	819,465	223,047
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.001 par value – 5,000 shares authorized; none issued and outstanding at March 31, 2024 and December 31, 2023	0	0
Common stock, $0.001 par value – $100,000 shares authorized; $31,326 shares issued and $31,097 shares outstanding at March 31, 2024, respectively; and $30,954 shares issued and outstanding at December 31, 2023	31	31
Additional paid-in capital	806,621	855,784
Accumulated other comprehensive loss	(89)	(112)
Accumulated deficit	(691,273)	(645,606)
Treasury stock, at cost; $229 and $0 shares at March 31, 2024 and December 31, 2023, respectively	(25,000)	0
Total stockholders’ equity	90,290	210,097
Total liabilities and stockholders’ equity	$ 909,755	$ 433,144
Treasury stock (in shares)	229	0

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2024	Dec. 31, 2023
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)	31,326,000	30,954,000
Common stock, shares outstanding (in shares)	31,097,000	30,954,000
Treasury stock (in shares)	229,000	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Income Statement [Abstract]
Revenue, net	$ 131,929	$ 111,436
Cost of revenue	44,413	35,755
Gross profit	87,516	75,681
Operating expenses:
Research and development	16,994	14,842
Selling, general and administrative	108,660	100,343
Total operating expenses	125,654	115,185
Loss from operations	(38,138)	(39,504)
Interest expense	(2,860)	(950)
Interest and other income, net	2,952	1,432
Loss on extinguishment of debt	(7,589)	0
Loss before income taxes	(45,635)	(39,022)
Income tax provision	32	87
Net loss	$ (45,667)	$ (39,109)
Net loss per common share, basic (in USD per share)	$ (1.47)	$ (1.29)
Net loss per common share, diluted (in USD per share)	$ (1.47)	$ (1.29)
Weighted-average shares, basic (in shares)	31,033	30,297
Weighted-average shares, diluted (in shares)	31,033	30,297

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (45,667)	$ (39,109)
Other comprehensive income (loss):
Net change in unrealized (loss) gain from marketable securities	(54)	327
Cumulative translation adjustment	77	0
Comprehensive loss	$ (45,644)	$ (38,782)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Cash flows from operating activities
Net loss	$ (45,667)	$ (39,109)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	5,131	3,576
Stock-based compensation	20,991	18,251
Amortization of premium and accretion of discounts, net	(908)	(1,137)
Amortization of operating lease right-of-use assets	1,244	1,365
Amortization of debt discount	578	0
Provision for doubtful accounts and contractual allowances	16,289	21,425
Loss on extinguishment of debt	7,589	0
Other	106	176
Changes in operating assets and liabilities:
Accounts receivable	(44,518)	(21,064)
Inventory	(923)	(1,404)
Prepaid expenses and other current assets	7,813	(1,053)
Other assets	(4,694)	(3,189)
Accounts payable and accrued liabilities	(12,877)	(8,966)
Deferred revenue	(238)	435
Operating lease liabilities	(1,945)	(59)
Net cash used in operating activities	(52,029)	(30,753)
Cash flows from investing activities
Purchases of property and equipment	(9,776)	(8,423)
Purchases of marketable securities	(2,426)	(33,757)
Maturities of marketable securities	52,200	46,000
Net cash provided by investing activities	39,998	3,820
Cash flows from financing activities
Proceeds from Braidwell debt	75,000	0
Proceeds from issuance of 2029 Notes	661,250	0
Purchases of capped call transactions	(72,407)	0
Purchase of treasury stock	(25,000)	0
Proceeds from issuance of common stock in connection with employee equity incentive plans	604	905
Net cash provided by financing activities	504,641	905
Effect of exchange rate changes on cash	(4)	0
Net increase (decrease) in cash, cash equivalents, and restricted cash	492,606	(26,028)
Cash, cash equivalents, and restricted cash, beginning of period	36,173	78,832
Cash, cash equivalents, and restricted cash, end of period	528,779	52,804
Supplemental disclosures of cash flow information:
Interest paid	1,595	678
Cash taxes paid	11	8
Cash received from tenant improvement allowances	0	1,603
Non-cash investing and financing activities:
Property and equipment costs included in accounts payable and accrued liabilities	23	203
Capitalized stock-based compensation in property and equipment	1,649	1,648
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect [Abstract]
Cash and cash equivalents	520,421	52,804
Restricted cash, long-term	8,358	0
Total cash, cash equivalents and restricted cash	528,779	52,804
SVB Term Loan
Cash flows from financing activities
Repayments of debt	(37,751)	0
Braidwell Term Loan Facility
Cash flows from financing activities
Repayments of debt	(78,660)	0
Payments of issuance costs	(1,803)	0
Convertible Notes Due 2029
Cash flows from financing activities
Payments of issuance costs	$ (16,592)	$ 0

Condensed Consolidated Statem_4

Condensed Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning balance (in shares) at Dec. 31, 2022		30,193
Beginning balance at Dec. 31, 2022	$ 239,812	$ 28	$ 762,380	$ (522,200)	$ (396)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with employee equity incentive plans, net (in shares)		270
Issuance of common stock in connection with employee equity incentive plans, net	905	$ 2	903
Stock-based compensation	19,899		19,899
Net loss	(39,109)			(39,109)
Net change in unrealized (loss) gain on marketable securities	327				327
Cumulative translation adjustment	0
Ending balance (in shares) at Mar. 31, 2023		30,463
Ending balance at Mar. 31, 2023	$ 221,834	$ 30	783,182	(561,309)	(69)
Beginning balance (in shares) at Dec. 31, 2023	30,954	30,954
Beginning balance at Dec. 31, 2023	$ 210,097	$ 31	855,784	(645,606)	(112)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock in connection with employee equity incentive plans, net (in shares)	9	372
Issuance of common stock in connection with employee equity incentive plans, net	$ 604		604
Purchase of capped call transactions	(72,407)		(72,407)
Purchase of treasury stock (in shares)		(229)
Purchase of treasury stock	(25,000)					(25,000)
Stock-based compensation	22,640		22,640
Net loss	(45,667)			(45,667)
Net change in unrealized (loss) gain on marketable securities	(54)				(54)
Cumulative translation adjustment	$ 77				77
Ending balance (in shares) at Mar. 31, 2024	31,097	31,097
Ending balance at Mar. 31, 2024	$ 90,290	$ 31	$ 806,621	$ (691,273)	$ (89)	$ (25,000)

ORGANIZATION AND DESCRIPTION OF

ORGANIZATION AND DESCRIPTION OF BUSINESS	3 Months Ended
	Mar. 31, 2024
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 leading digital healthcare company that creates trusted solutions that detect, predict, and prevent disease. The Company's principal business is the design, development, and commercialization of device-based technology to provide remote cardiac monitoring services that it believes allow clinicians to diagnose certain arrhythmias quicker and with greater efficiency than other services that rely on traditional technology. Since first receiving clearance from the U.S. Food and Drug Administration (“FDA”) for the Company's technology in 2009, the Company has supported physician and patient use of its technology and provided remote cardiac monitoring services from its Medicare-enrolled independent diagnostic testing facilities (“IDTFs”) and its qualified technicians. The Company has provided the Zio remote cardiac monitoring services, including extended Holter, traditional Holter, and mobile cardiac telemetry (“MCT”) monitoring services (“Zio Services”), using the Zio Systems. The Company is headquartered in San Francisco, California, which also serves as a clinical center. The Company has additional clinical centers in Deerfield, Illinois and Houston, Texas and a manufacturing facility in Cypress, California.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying financial statements include the accounts of the Company and its wholly owned subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. As permitted under those rules, the condensed consolidated financial statements and related disclosures as of December 31, 2023 have been derived from the audited consolidated financial statements but do 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 unaudited condensed consolidated financial information. The results of operations for the three months ended March 31, 2024, are not necessarily indicative of the results to be expected for the year ending December 31, 2024, or for any other interim period or for any other future year. The accompanying 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, 2023, included in the Company’s Annual Report on Form 10-K, filed with the SEC on February 22, 2024. Risks and Uncertainties Macroeconomic Factors and Supply Chain Constraints The Company’s operations and performance may vary based on worldwide economic and political conditions, which have been adversely impacted by continued global economic uncertainty, political instability, and military hostilities in multiple geographies including ongoing geopolitical conflicts, such as the war in Ukraine and conflict in the Middle East, domestic and global inflationary trends, interest rate volatility, uncertainty with respect to the federal budget and debt ceiling and potential government shutdowns related thereto, potential instability in the global banking system, global supply shortages, and a tightening labor market. A severe or prolonged economic downturn or period of global political instability could drive hospitals and other healthcare professionals to tighten budgets and curtail spending, which could in turn negatively impact rates at which physicians prescribe the Company’s Zio Services. In addition, higher unemployment rates or reductions in employer-provided benefits plans could result in fewer commercially insured patients, resulting in a reduction in the Company’s margins and impairing the ability of uninsured patients to make timely payments. A weak or declining economy could also strain the Company’s suppliers, possibly resulting in supply delays and disruptions. There is also a risk that one or more of the Company’s current service providers, suppliers, or other partners may not survive such difficult economic times, which could directly affect the Company’s ability to attain its goals on schedule and on budget. If the current equity and credit markets deteriorate, it may make any necessary debt or equity financing more difficult, more costly, and more dilutive. The Company cannot predict the timing, strength, or duration of an economic downturn, instability, or recovery, whether worldwide, in the United States, or within its industry. The Company’s hybrid work arrangements and decision to pursue a sublease for its leased San Francisco headquarters resulted in an impairment of its right-of-use ("ROU") asset and related leasehold improvements and furniture and fixtures during the year ended December 31, 2022. In the fourth quarter of 2023, the Company recorded an additional impairment of its ROU asset and related leasehold improvements and furniture and fixtures related to its leased San Francisco headquarters, due to a continued soft real estate rental market within the city proper San Francisco, California. As the Company continues to evaluate its global real estate footprint, the Company may incur additional impairment charges related to real property lease agreements. The Company is continuously reviewing its liquidity and anticipated capital requirements. The Company believes it has adequate liquidity over the next 12 months to operate its business and to meet its cash requirements. Reimbursement The Company receives revenue for the Zio Services primarily from third-party payors, which include commercial payors and government agencies, such as the Centers for Medicare & Medicaid Services (“CMS”). Third-party payors require the Company to identify the service for which it is seeking reimbursement by using a Current Procedural Terminology (“CPT”) code set maintained by the American Medical Association. These CPT codes are subject to periodic change and update, which will impact the reimbursement rates for the Company’s Zio Services. Based on relative value units, CMS annually updates the reimbursement rates for diagnostic tests performed by IDTFs via the Medicare Physician Fee Schedule. CMS establishes national payment rates for the CPT codes the Company uses to report the long-term Holter monitoring services it performs with its Zio XT System: CPT codes 93247 (for wear-time of greater than 7 days and up to 15 days) and 93243 (for wear-time of greater than 48 hours and up to 7 days). Because remote cardiac monitoring technology, including the Zio System, is rapidly evolving, there is a continuing risk that relative value units assigned, and reimbursement rates set, by CMS may not adequately reflect the value and expense of this technology and associated monitoring services, and CMS may reduce these rates in the future, which would adversely affect the Company’s financial results. Use of Estimates The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the periods presented. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, contractual allowances, allowance for doubtful accounts, the useful lives of property and equipment, the recoverability of long-lived assets, including the estimated usage of the printed circuit board assemblies (“PCBAs”), the incremental borrowing rate for operating leases, accounting for income taxes, impairment of ROU assets, and various inputs used in estimating stock-based compensation. Actual results may differ from those estimates. Significant Accounting Policies During the three months ended March 31, 2024, there were no changes to the Company’s significant accounting policies as described in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2023, with the exception of the following: Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Under the terms of certain facility operating lease agreements, the Company is required to maintain a letter of credit as collateral during the term of the lease. As of March 31, 2024, restricted cash of $8.4 million was pledged as collateral under the letter of credit with Silicon Valley Bank. 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, U.S. 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 and their dispersion across many geographies. The Company does not require collateral. During the first quarter of 2024, the Company experienced a temporary delay in the billing of the Company's contracted and non-contracted payer customers, performed by the Company's third-party claims processing vendor. The delay was due to a cybersecurity incident experienced by Change Healthcare, a division of UnitedHealth Group, which the Company's third-party vendor engages for services relating to billing and collections. While the Company substantially cleared the billing backlog as of the end of the first quarter of 2024, the delay in billing resulted in a temporary delay in the Company's cash collections. The Company records an allowance for doubtful accounts based on the assessment of the collectability of customer accounts, considering factors such as historical experience, credit quality, the age of the accounts receivable balances, and current economic conditions that may affect a customer’s ability to pay. CMS accounted for approximately 24% of the Company's revenue for each of the three months ended March 31, 2024 and 2023. CMS accounted for 24% and 25% of accounts receivable at March 31, 2024 and December 31, 2023, respectively. One commercial customer accounted for approximately 12% of the Company's accounts receivable at March 31, 2024. Inflationary Risk The Company continuously monitors the effects of inflationary factors, such as increases in cost of goods sold and selling and operating expenses, which may adversely affect its results of operations. Specifically, the Company may experience inflationary pressure affecting freight costs, the cost of the components for the Company’s Zio Services, overhead costs relating to maintenance of the Company’s facilities, and in the wages paid to its employees due to challenging labor market conditions. Competitive and regulatory conditions may restrict the Company’s ability to fully recover these costs through price increases. As a result, it may be difficult to fully offset the impact of persistent inflation. The Company’s inability or failure to do so could have a material adverse effect on its business, financial condition and results of operations or cause the Company to need to obtain additional capital earlier than anticipated in the future. Supply Risk The Company relies on single-source vendors to supply some of its disposable housings, instruments and other materials used to manufacture the Zio patches and the adhesive that binds the Zio patch to a patient’s body. These components and materials are critical, and there could be a considerable delay in finding alternative sources of supply. Recent Accounting Pronouncements In November 2023, the FASB issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which updates reportable segment disclosure requirements primarily through enhanced disclosures about significant segment expenses. The amendments are effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating this ASU to determine its impact on the Company's consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU No. 2023-09 (“ASU 2023-09”), Income Taxes (Topic 740): Improvement to Income Tax Disclosures to enhance the transparency and decision usefulness of income tax disclosures. Two primary enhancements related to this ASU include disaggregating existing income tax disclosures relating to the effective tax rate reconciliation and income taxes paid. ASU 2023-09 is effective for annual periods beginning after December 15, 2024 on a prospective basis. Early adoption is permitted. The Company is currently evaluating the impact of this accounting standard update on the Company's consolidated financial statements and related disclosures. On March 6, 2024, the SEC adopted SEC Release Nos. 33-11275; 34-99678, The Enhancement and Standardization of Climate-Related Disclosures for Investor , to require the disclosure of certain climate-related information in registration statements and annual reports, including Scope 1 and 2 emissions and information about climate-related risks that have materially impacted, or are reasonably likely to have a material impact on, a company’s business strategy, results of operations, or financial condition. In addition, under the final rules, certain disclosures related to severe weather events and other natural conditions will be required in audited financial statements. The disclosure requirements will begin phasing in for the Company's reports and registration statements including financial information in the fiscal year ending December 31, 2025. On April 4, 2024, the SEC issued an order staying the final rules until the completion of judicial review. The Company is currently evaluating the impact of this final rule on the Company's consolidated financial statements and related disclosures.

REVENUE AND ACCOUNTS RECEIVABLE

REVENUE AND ACCOUNTS RECEIVABLE	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
REVENUE AND ACCOUNTS RECEIVABLE	REVENUE AND ACCOUNTS RECEIVABLE 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 the three months ended March 31, 2024 and 2023 were as follows (in thousands, except percentages): Three Months Ended March 31, 2024 2023 Amount % of Revenue Amount % of Revenue Contracted third-party payors $ 71,773 54% $ 61,907 56% Centers for Medicare and Medicaid 31,786 24% 26,491 24% Healthcare institutions 19,571 15% 15,781 14% Non-contracted third-party payors 8,799 7% 7,257 6% Total $ 131,929 $ 111,436 Revenue generated from the United States comprised substantially all of the Company's revenue. No other country comprised 10% or greater of the Company's revenue during the three months ended March 31, 2024 and 2023. Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowances 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 unaudited condensed consolidated balance sheets net of an estimated allowance for doubtful accounts and contractual allowances. The Company establishes an allowance for doubtful accounts for estimated uncollectible receivables based on its assessment of the collectability of customer accounts 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 for services performed. Such provisions are based on the Company's historical experience and are reported as a reduction of revenue. The Company regularly reviews the allowances by considering factors such as historical experience, credit quality, the age of the accounts receivable balances, and current economic conditions that may affect a customer’s ability to pay. The following table presents the changes in the allowance for doubtful accounts (in thousands): Three Months Ended Year Ended Three Months Ended Balance, beginning of period $ 20,289 $ 18,475 $ 18,475 Provision for doubtful accounts 6,037 17,105 5,326 Write-offs, net of recoveries and other adjustments (6,337) (15,291) (4,726) Balance, end of period $ 19,989 $ 20,289 $ 19,075 The following table presents the changes in the contractual allowance (in thousands): Three Months Ended Year Ended Three Months Ended Balance, beginning of period $ 52,689 $ 41,389 $ 41,389 Add: provision for contractual adjustments 10,252 52,523 16,099 Less: contractual adjustments (10,870) (41,223) (9,457) Balance, end of period $ 52,071 $ 52,689 $ 48,031 Contract Liabilities ASC 606, Revenue from Contracts with Customers, 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 revenue when Zio reports are delivered to the healthcare provider. During the three months ended March 31, 2024 and 2023, $3.0 million and $2.7 million relating to the contract liability balance at the beginning of 2024 and 2023 was recognized as revenue, respectively. The advance payments liability was $3.1 million and $3.3 million as of March 31, 2024 and December 31, 2023, respectively. Contract Costs Under ASC 340, Other Assets and Deferred Costs ("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.

CASH EQUIVALENTS AND MARKETABLE

CASH EQUIVALENTS AND MARKETABLE SECURITIES	3 Months Ended
	Mar. 31, 2024
Cash Equivalents And Investments [Abstract]
CASH EQUIVALENTS AND MARKETABLE SECURITIES	CASH EQUIVALENTS AND MARKETABLE SECURITIES The fair value of cash equivalents and marketable securities as of March 31, 2024 and December 31, 2023, were as follows (in thousands): March 31, 2024 Amortized Gross Unrealized Fair Value Gains Losses Money market funds $ 28,789 $ — $ — $ 28,789 U.S. government securities 48,668 6 (3) 48,671 Total cash equivalents and marketable securities $ 77,457 $ 6 $ (3) $ 77,460 Classified as: Cash equivalents $ 28,789 Marketable securities 48,671 Total cash equivalents and marketable securities $ 77,460 December 31, 2023 Amortized Gross Unrealized Fair Value Gains Losses Money market funds $ 12,594 $ — $ — $ 12,594 U.S. government securities 97,534 59 (2) 97,591 Total cash equivalents and marketable securities $ 110,128 $ 59 $ (2) $ 110,185 Classified as: Cash equivalents $ 12,594 Marketable securities 97,591 Total cash equivalents and marketable securities $ 110,185

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Assets and Liabilities Measured at Fair Value on a Recurring Basis 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 U.S. 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 Company holds a strategic equity investment that it does not measure at fair value on a recurring basis. The carrying value of this investment is $3.0 million as of March 31, 2024 and December 31, 2023. The Company includes this investment in other assets in its unaudited condensed consolidated balance sheets. Additionally, in April 2024, the Company made a $10.0 million strategic loan investment in a private company. The loan investment can convert into preferred shares of the private company based upon certain qualifying financing events. 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): March 31, 2024 Level 1 Level 2 Level 3 Total Assets Money market funds $ 28,789 $ — $ — $ 28,789 U.S. government securities — 48,671 — 48,671 Total $ 28,789 $ 48,671 $ — $ 77,460 December 31, 2023 Level 1 Level 2 Level 3 Total Assets Money market funds $ 12,594 $ — $ — $ 12,594 U.S. government securities — 97,591 — 97,591 Total $ 12,594 $ 97,591 $ — $ 110,185 The Company's debt obligation as of December 31, 2023 is classified as Level 2 input. The fair value of the Company’s outstanding interest-bearing obligation as of December 31, 2023 approximated the carrying value of $35.0 million. Fair Value of Senior Convertible Notes The fair value, based on a quoted market price (Level 1), of the Company’s senior convertible notes due 2029 (the "2029 Notes") is as follows (in thousands): March 31, 2024 December 31, 2023 Senior Convertible Notes due 2029 $ 706,215 $ —

BALANCE SHEET COMPONENTS

BALANCE SHEET COMPONENTS	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BALANCE SHEET COMPONENTS	BALANCE SHEET COMPONENTS Inventory Inventory consisted of the following (in thousands): March 31, 2024 December 31, 2023 Raw materials and work-in-progress $ 6,419 $ 6,299 Finished goods 8,454 7,674 Total $ 14,873 $ 13,973 Other Assets Other assets consisted of the following (in thousands): March 31, 2024 December 31, 2023 PCBAs $ 42,180 $ 38,987 Cloud computing arrangements 6,566 4,959 Strategic investment 3,000 3,000 Other 987 1,093 Total $ 52,733 $ 48,039 The Company reuses PCBAs in each wearable Zio Monitor patch, Zio XT patch, and Zio AT patch, as well as the wireless gateway used in conjunction with the Zio AT patch. As PCBAs are used in a wearable Zio Monitor patch, Zio XT patch, or Zio AT patch, a portion of the cost of the PCBA is recorded as a cost of revenue. The PCBAs are charged over a period beyond one year. Charges to cost of revenue were $2.8 million and $1.4 million for the three months ended March 31, 2024 and 2023, respectively. During the three months ended March 31, 2024, PCBAs increased by $3.2 million primarily related to the purchase of PCBAs to support the expanded launch of the Zio Monitor System. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): March 31, 2024 December 31, 2023 Laboratory and manufacturing equipment $ 7,169 $ 6,007 Computer equipment and software 4,035 3,905 Furniture and fixtures 4,180 4,020 Leasehold improvements 27,118 24,885 Internal-use software 64,321 61,980 Internal-use software in development 52,245 43,701 Construction in progress 8,840 10,119 Total property and equipment, gross 167,908 154,617 Less: accumulated depreciation and amortization (55,634) (50,503) Total property and equipment, net $ 112,274 $ 104,114 Depreciation and amortization expense for the three months ended March 31, 2024 and 2023 was $5.1 million and $3.6 million, respectively, of which amortization related to internal-use software, was $3.7 million and $2.7 million for the three months ended March 31, 2024 and 2023, respectively. During the three months ended March 31, 2024, internal-use software, both in service and in development, increased by $10.9 million. This increase related to enhancements in the Company’s core technology, products and services and artificial intelligence, as well as investment in future technology, such as the Zio Monitor System, the Company's next generation biosensor technology platform. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued payroll and related expenses $ 24,995 $ 47,656 Accrued vacation 9,924 8,608 Accrued expenses 19,546 14,891 Claims payable 5,032 4,578 Accrued employee share purchase plan contributions 2,958 1,037 Accrued state and foreign income and sales taxes 2,953 2,877 Accrued professional services fees 4,636 3,715 Total accrued liabilities $ 70,044 $ 83,362

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Leases The Company leases office, manufacturing, and clinical centers under non-cancelable operating leases which expire on various dates through 2033 . These leases generally contain scheduled rent increases or escalation clauses and renewal options. Operating lease ROU 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 ROU 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 ROU asset as they are based on actual usage. The Company recognizes operating lease expenses, generally on a straight-line basis over the lease period. During the three months ended March 31, 2024, there were no material changes to the leases from those described in Note 8, Commitments and Contingencies , included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023. Contractual obligations under operating lease liabilities were as follows (in thousands): Year Ended December 31: 2024 (remainder of the year) $ 10,670 2025 15,627 2026 16,090 2027 16,486 2028 16,379 Thereafter 47,098 Total lease payments 122,350 Less: imputed interest (29,421) Total lease liabilities $ 92,929 Legal Proceedings From time to time, the Company is involved in claims and legal proceedings or investigations, that arise in the ordinary course of business. Such matters could have an adverse impact on the Company's reputation, business, and financial condition and divert the attention of its management from the operation of the Company's business. These matters are subject to many uncertainties and outcomes that are not predictable. On February 1, 2021, a putative class action lawsuit was filed in the United States District Court for the Northern District of California (the "Court") alleging that the Company and its former Chief Executive Officer, Kevin M. King, violated Sections 10(b) and 20(a) of the Exchange Act and SEC Rule 10b-5 promulgated thereunder. On August 2, 2021, the lead plaintiff filed an amended complaint, and filed a further amended complaint on September 24, 2021. The amended complaint names as defendants, in addition to the Company and Mr. King, its former Chief Executive Officer, Michael J. Coyle, and former Chief Financial Officer and former Chief Operating Officer, Douglas J. Devine. The purported class in the amended complaint includes all persons who purchased or acquired the Company's common stock between August 4, 2020 and July 13, 2021, and seeks unspecified damages purportedly sustained by the class. On October 27, 2021, the Company filed a motion to dismiss, which the Court granted on March 31, 2022, entering judgment in favor of the Company and the other defendants. On April 29, 2022, the original named plaintiff appealed to the Ninth Circuit Court of Appeals. On October 11, 2023, after briefing by the parties and oral argument, the Ninth Circuit dismissed the appeal for lack of jurisdiction. The appellant filed a petition for rehearing en banc, which was denied on December 6, 2023. On February 6, 2024, a second putative class action lawsuit was filed in the Court alleging that the Company's current Chief Executive Officer, Quentin Blackford, the Company's current Chief Financial Officer, Brice Bobzien, and Mr. Devine violated Sections 10(b) and 20(a) of the Exchange Act and SEC Rule 10b-5 promulgated thereunder, and seeks unspecified damages purportedly sustained by the class. The Company believes the above securities class action lawsuits to be without merit and plans to continue to defend itself vigorously. On March 26, 2021, the Company received a grand jury subpoena from the U.S. Attorney’s Office for the Northern District of California requesting information related to communications with FDA and the Company's products and services. On September 13, 2021, the Company received a second subpoena requesting additional information. On April 4, 2023, the Company received a Subpoena Duces Tecum from the Consumer Protection Branch, Civil Division of the U.S. Department of Justice, requesting production of various documents regarding the Company’s products and services. The Company is cooperating fully on these matters. On February 20, 2024, Welch Allyn, a subsidiary of Hill-Rom Holdings, Inc. which was acquired by Baxter International, Inc., filed a lawsuit against the Company in the United States District Court for the District of Delaware, alleging that the Company's Zio patches infringe certain of its patents and that iRhythm’s infringement was willful. We filed a motion to dismiss Welch Allyn’s willful infringement claims on April 11, 2024. Welch Allyn filed an amended complaint on April 24, 2024 that continues to allege that our Zio devices infringe certain of its patents and that iRhythm’s infringement was willful. Welch Allyn seeks money damages and attorneys’ fees. The Company believes this lawsuit is without merit and plans to defend itself vigorously. Development Agreement On September 3, 2019, the Company entered into a Development Collaboration Agreement with Verily Life Sciences LLC, an Alphabet company (“VLS”) and Verily Ireland Limited (“VIL” and together with VLS, “Verily”) (such Development Collaboration Agreement, as amended by Amendment No. 1 dated April 26, 2021 and Amendment No.2 dated January 24, 2022, the “Development Agreement”). The Development Agreement 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 Development 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 (“Afib”) screening, detection, or monitoring products pursuant to the Development Agreement, which products will involve combining Verily's and the Company’s technology platforms and capabilities. Under the terms of the Development Agreement, the Company paid Verily an upfront fee of $5.0 million in 2019. In addition, the Company agreed to make additional milestone payments to Verily up to an aggregate of $12.75 million upon achievement of various development and regulatory milestones over the term of the Development Agreement. The Company has achieved milestones tied to payments totaling $11.0 million to date and expect to make additional payments over the term of the Development Agreement of $1.75 million, subject to the achievement of specified milestones. The Development Agreement provides each party with licenses to use certain intellectual property of the other party for development activities in the field of Afib 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. 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 the Company, 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

DEBT	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
DEBT	DEBT 1.50% Senior Convertible Notes due 2029 The carrying amounts of the Company’s 2029 Notes were as follows (in thousands): March 31, 2024 December 31, 2023 Principal amount $ 661,250 $ — Unamortized debt issuance costs (17,174) — Carrying amount of senior convertible notes due 2029 $ 644,076 $ — The following table summarizes the components of interest expense and the effective interest rate for the 2029 Notes for the periods shown (in thousands): Three Months Ended March 31, 2024 2023 Contractual coupon interest $ 689 $ — Amortized debt issuance costs 399 — Total interest expense recognized on senior convertible notes due 2029 $ 1,088 $ — Effective interest rate 2.0 % — % On March 7, 2024, the Company completed an offering of $661.3 million aggregate principal amount of unsecured senior convertible notes with a stated interest rate of 1.50% and a maturity date of September 1, 2029. The proceeds include the full exercise of the option granted by the Company to the initial purchasers of the 2029 Notes to purchase up to an additional $86.3 million aggregate principal amount of notes. Interest on the 2029 Notes is payable semi-annually in arrears on March 1 and September 1 of each year, beginning on September 1, 2024. The net proceeds from the offering, after deducting initial purchasers’ discounts and estimated costs directly related to the offering, were approximately $643.6 million. The initial conversion rate of the 2029 Notes is 6.7927 shares per $1,000 principal amount of notes, which is equivalent to a conversion price of approximately $147.22 per share, subject to adjustments. The 2029 Notes may be settled in cash, stock, or a combination thereof, solely at the Company's discretion. The Company used net proceeds from the offering to purchase capped calls, as well as repayment of the Company's outstanding debt which is described below. In addition, the Company also used net proceeds from the offering to repurchase shares of the Company's common stock. Refer to Note 10, Stockholders' Equity for further details relating to the Company's shares repurchase. No principal payments are due on the 2029 Notes prior to maturity. Other than restrictions relating to certain fundamental changes and consolidations, mergers or asset sales and customary anti-dilution adjustments, the indenture relating to the 2029 Notes (the “Indenture”) includes customary terms and covenants, including certain events of default after which the 2029 Notes may be due and payable immediately. The Company uses the if-converted method for assumed conversion of the 2029 Notes to compute the weighted-average shares of common stock outstanding for diluted earnings per share, when applicable. Conversion Rights at the Option of the Holders Holders of the 2029 Notes who convert their notes in connection with a make-whole fundamental change (as defined in the Indenture) or convert their 2029 Notes called (or deemed called) for redemption in connection with any optional redemption are, under certain circumstances, entitled to an increase in the conversion rate. Additionally, in the event of a fundamental change (as defined in the Indenture), holders of the 2029 Notes may require the Company to repurchase for cash all or a portion of their notes at a price equal to 100% of the principal amount of notes, plus any accrued and unpaid interest to, but excluding, the repurchase date. Holders of the 2029 Notes may convert all or a portion of their notes prior to the close of business on the business day immediately preceding June 1, 2029, in multiples of $1,000 principal amount, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2024 (and only during such calendar quarter), if the last reported sale price of the Company's common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price of the 2029 Notes on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined in the Indenture) per $1,000 principal amount of the 2029 Notes for each trading day of that measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the conversion rate of the 2029 Notes on such trading day; (3) if the Company calls any or all 2029 Notes for redemption, at any time prior to the close of business on the scheduled trading day immediately preceding the redemption date, but only with respect to the 2029 Notes called (or deemed called) for redemption; or (4) upon the occurrence of specified corporate events as specified in the Indenture. On or after June 1, 2029, until 5:00 p.m., New York City time, on the second scheduled trading day immediately preceding September 1, 2029, holders of the notes may convert the 2029 Notes, in multiples of $1,000 principal amount, at their option regardless of the foregoing circumstances. Conversion Rights at Our Option The Company may not redeem the 2029 Notes prior to September 5, 2027. On or after September 5, 2027 and prior to June 1, 2029, the Company may redeem at its option for cash all or any portion of the 2029 Notes, at the redemption price, if the last reported sale price of the Company's common stock has been at least 130% of the conversion price then in effect for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending on, and including, the trading day immediately preceding the date on which the Company provides the redemption notice. The redemption price will be equal to 100% of the principal amount of the 2029 Notes, plus accrued and unpaid interest, if any, to, but excluding, the redemption date. 2029 Capped Call Transactions On March 4, 2024, in connection with the offering of the 2029 Notes, the Company entered into privately negotiated capped call transactions (the “2029 Capped Calls”) with certain financial institutions. The 2029 Capped Calls will cover, subject to anti-dilution adjustments substantially similar to those applicable to the 2029 Notes, the number of shares of the Company's common stock that will initially underlie the 2029 Notes. The 2029 Capped Calls are expected generally to reduce potential dilution to the Company's common stock upon conversion of the 2029 Notes and/or offset any cash payments that the Company could be required to make in excess of the principal amount of converted 2029 Notes, as the case may be, with such reduction and/or offset subject to a cap. The 2029 Capped Calls have an initial cap price of $218.10 per share, subject to adjustments, which represents a premium of 100% over the closing price of the Company's common stock of $109.05 per share on the Nasdaq Global Select Market on March 4, 2024. The Company completed the purchase of the 2029 Capped Calls on March 7, 2024, for the amount of $72.4 million. The cost to purchase the 2029 Capped Calls was recorded as a reduction to additional paid-in capital in the Company's consolidated balance sheets, as the 2029 Capped Calls met the criteria for classification within stockholders’ equity. Braidwell Debt On January 3, 2024 (the “Closing Date”), the Company entered into the Credit, Security and Guaranty Agreement (the “Braidwell Credit Agreement”) with Braidwell Transactions Holdings LLC – Series 5 (“Braidwell”), which provided for a senior secured term loan in an aggregate principal amount of up to $150.0 million (the “Braidwell Term Loan Facility”). An initial tranche of $75.0 million (“Initial Loan”) was funded on the Closing Date. In addition to the Initial Loan, the Braidwell Term Loan Facility included an additional tranche of $75.0 million, which was accessible by the Company through the one year anniversary of the Closing Date, so long as the Company satisfied certain customary conditions. The Braidwell Term Loan Facility had a maturity date of January 3, 2029 (the “Maturity Date”) and provided, at the Company’s election, for the option to have a portion of interest added to principal rather than paid in cash during the term of the loan, with principal and accrued interest due at the Maturity Date. On March 7, 2024, in connection with the offering of the 2029 Notes, the Company used approximately $80.2 million of the net proceeds for the repayment in full of the $75.0 million outstanding Initial Loan, as well as interest, fees and expenses associated with terminating the agreement. Interest expense for the three months ended March 31, 2024 was $1.8 million, consisting of contractual coupon interest and amortized debt issuance costs of $1.6 million and $0.2 million, respectively. The Company incurred $5.6 million of fees and expenses relating to the repayment of the Initial Loan and the termination of the Braidwell Credit Agreement, inclusive of unamortized debt origination costs, which has been recorded within loss on extinguishment of debt in the Company’s condensed consolidated statements of income during the three months ended March 31, 2024. SVB Term Loan In October 2018, the Company entered into the Third Amended and Restated Loan and Security Agreement (“SVB Loan Agreement”) with Silicon Valley Bank (“SVB”). Under the SVB Loan Agreement, the Company had borrowed $35.0 million and had made repayments through March 2022, at which time the outstanding balance was $18.5 million. On March 28, 2022, the Company entered into a Second Amendment (“2022 Amendment”) to its SVB Loan Agreement which provided for a term loans facility in the aggregate principal amount of up to $75.0 million (the “2022 Term Loans”), of which $35.0 million was borrowed at closing and a portion of the proceeds was used to pay in full the outstanding balance of $18.5 million under the SVB Loan Agreement. None of the remaining $40.0 million of the 2022 Term Loans was borrowed up through December 31, 2023. The 2022 Amendment also amended the terms of the revolving credit line under the SVB Loan Agreement, which provided for an aggregate principal amount of $25.0 million. On January 3, 2024, in connection with the entry into the Braidwell Credit Agreement, the Company used approximately $37.8 million of the net proceeds for the repayment in full of the $35.0 million outstanding principal balance as well as interest, fees and expenses associated with terminating the agreement. Upon termination of the SVB Loan Agreement, SVB’s security interest in the Company’s assets and property was released. Interest expense for the three months ended March 31, 2024 and 2023 was de minimis and $0.8 million, respectively. Contractual coupon interest for the three months ended March 31, 2024 and 2023 was de minimis and $0.7 million, respectively. Amortized debt issuance costs for the three months ended March 31, 2024 and 2023 was de minimis. The Company incurred $2.0 million of fees and expenses relating to the termination of the SVB Loan Agreement, which has been recorded within loss on extinguishment of debt in the Company’s condensed consolidated statements of income during the three months ended March 31, 2024.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2024
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company recorded a tax provision related to its U.S. state taxes and its foreign subsidiaries during the three months ended March 31, 2024 and 2023. 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 net operating loss carryforwards and other deferred tax assets.

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
STOCKHOLDERS' EQUITY	STOCKHOLDERS' EQUITY Common Stock The Company’s amended and restated certificate of incorporation dated October 25, 2016, as amended, authorizes the Company to issue 100,000,000 shares of common stock with a par value of $0.001 per share and 5,000,000 shares of preferred stock with a par value of $0.001 per share. The holders of common stock are entitled to receive dividends whenever funds and assets are legally available and when declared by the Board, subject to the prior rights of holders of all series of convertible preferred stock outstanding. No dividends were declared through March 31, 2024. The Company had reserved shares of common stock for the equity incentive plan issuances as follows (in thousands): March 31, 2024 December 31, 2023 Options issued and outstanding 298 307 Unvested restricted stock units and performance-based restricted stock units 1 2,699 2,438 Shares available for grant under future stock plans 1 6,141 6,765 Shares available for future issuance 9,138 9,510 1 PRSUs are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative Total Shareholder Return ("TSR"), as discussed in Note 11, Equity Incentive Plan and Stock-Based Compensation. On March 7, 2024, the Company used approximately $25.0 million of the net proceeds from the 2029 Notes offering to repurchase 229,252 shares of the Company's common stock at a purchase price of $109.05 per share via privately negotiated transactions effected through one of the initial purchasers or its affiliate. Repurchased shares of the Company's common stock are held as treasury shares until they are reissued or retired.

EQUITY INCENTIVE PLAN AND STOCK

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION	EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION A summary of awards available for grant under the Company’s 2016 Equity Incentive Plan is as follows (in thousands): Shares Available for Grant Balance as of December 31, 2023 6,765 Awards granted 1 (751) Awards forfeited 1 127 Balance as of March 31, 2024 6,141 1 Awards granted and forfeited include PRSUs, which are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative TSR, as described below . Restricted Stock Units and Performance-Based Restricted Stock Units The fair value of RSUs and PRSUs are based on the Company’s closing stock price on the date of grant. The fair value of market based PRSUs were estimated at the date of grant using the Monte-Carlo option pricing model. A summary is as follows (in thousands, except weighted average grant date fair value): Restricted Stock Units Performance Based Restricted Stock Units and Market-Based Units Shares Underlying RSUs Weighted Average Grant Date Fair Value Shares Underlying PRSUs 1 Weighted Average Grant Date Fair Value Balance as of December 31, 2023 1,542 $ 117.90 896 $ 121.80 Granted 503 118.05 248 133.50 Vested (301) 124.95 (62) 77.50 Forfeited (37) 115.01 (90) 85.11 Balance as of March 31, 2024 1,707 $ 116.76 992 $ 130.60 1 Based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on the annual unit volume compound annual growth rate ("CAGR") as described below. As of March 31, 2024, there was total unamortized compensation costs of $163.5 million, net of estimated forfeitures, related to RSUs, which the Company expects to recognize over a weighted average period of 1.9 years. Aggregate intrinsic value of the RSUs was $198.1 million as of March 31, 2024. As of March 31, 2024, there was total unamortized compensation costs of $54.0 million, net of estimated forfeitures, related to PRSUs, which the Company expects to recognize over a weighted average remaining period of 2.2 years. Aggregate intrinsic value of the PRSUs was $114.9 million as of March 31, 2024. Market-based PRSUs The Company grants PRSUs to its key executives. PRSUs can be earned in accordance with the performance equity program for each respective grant. For further details on PRSUs granted in 2023 and prior years, please refer to Note 13, Equity Incentive Plans , in the financial statements accompanying the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. In February 2024, the Company granted market-based PRSUs to senior executive officers. These PRSUs to be earned will be based on the CAGR calculated between fiscal year 2026 and fiscal year 2023 annual unit volume and measuring performance thresholds mentioned above, as well as a relative comparison of the S&P Healthcare Equipment Select Industry Index to the Company's Total Shareholder Return (“TSR”). The grant date fair value of the TSR was based on the expected term of 2.8 years, interest risk free rate of 4.4%, implied volatility of 67.95% and no dividend yield. These February 2024 awards are subject to the recipient senior executive officer's continued employment through the vesting date of March 16, 2027. Options The following table summarizes stock option activity: Options Outstanding Options Outstanding (in thousands) Weighted- Weighted- Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2023 307 $ 42.34 3.29 $ 19,859 Options exercised (9) 67.54 Balance as of March 31, 2024 298 41.58 3.13 22,176 Options exercisable – March 31, 2024 298 $ 41.58 3.13 $ 22,176 There have been no options granted since December 31, 2019. As of March 31, 2024, the options were fully vested. Employee Stock Purchase Plan During the three months ended March 31, 2024 there were no material changes to the ESPP from those described in Note 13, Equity Incentive Plans , included in the Company's Annual Report on Form 10-K for the year ended December 31, 2023. As of March 31, 2024, the Company had $2.9 million of unrecognized compensation expense that will be recognized over a weighted average period of 0.5 years. Stock-Based Compensation Expense The following table summarizes the total stock-based compensation expense included in the unaudited condensed consolidated statements of operations for the three months ended March 31, 2024 and 2023 (in thousands): Three Months Ended March 31, 2024 2023 Cost of revenue $ 846 $ 564 Research and development 3,596 2,387 Selling, general and administrative 16,549 15,300 Total stock-based compensation expense $ 20,991 $ 18,251

NET LOSS PER SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE As the Company had net losses for the three months ended March 31, 2024 and 2023, all potential common shares were determined to be anti-dilutive. The following table sets forth the computation of the basic and diluted net loss per share during the three months ended March 31, 2024 and 2023 (in thousands, except per share data): Three Months Ended March 31, 2024 2023 Numerator: Net loss $ (45,667) $ (39,109) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 31,033 30,297 Net loss per common share, basic and diluted $ (1.47) $ (1.29) In accordance with ASU No. 2020-06, Debt with Conversion and Other Options (Subtopic 470-20), the Company applies the if-converted method in computing the effect of the Company's senior convertible notes on diluted net income per share. For periods in which the Company reports net income, the numerator of the diluted per share computation is adjusted for interest expense and amortization of debt issuance costs, net of tax, and the denominator is adjusted for the weighted average number of shares into which each of the Company’s senior convertible notes could be converted. The effect is only included in the calculation of diluted net income per share for those senior convertible notes which reduce net income per share. The following outstanding shares of potentially dilutive securities have been excluded from diluted net loss per common share for the three months ended March 31, 2024 and 2023 because their inclusion would be anti-dilutive (in thousands): Three Months Ended March 31, 2024 2023 Options to purchase common stock 298 311 RSUs and PRSUs 1 unvested 2,699 2,523 Senior convertible notes 4,492 — Total 7,489 2,834 1 PRSUs are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative TSR, as discussed in Note 11, Equity Incentive Plan and Stock-Based Compensation.

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (45,667)	$ (39,109)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false
Mark J Day [Member]
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On March 13, 2024, Mark J. Day, the Company's then Chief Technology Officer, entered into a prearranged written stock sale plan in accordance with Rule 10b5-1 (the “Day Rule 10b5-1 Plan”) under the Exchange Act for the sale of shares of the Company’s common stock. The Day Rule 10b5-1 Plan was entered into during an open trading window in accordance with the Company’s policies regarding transactions in the Company’s securities and is intended to satisfy the affirmative defense of Rule 10b5-1(c) under the Exchange Act. The Day Rule 10b5-1 Plan provides for the potential sale of up to 6,090 shares of the Company’s common stock, including upon the vesting and settlement of restricted stock units and performance restricted stock units for shares of the Company’s common stock, so long as the market price of the Company’s common stock is higher than certain minimum threshold prices specified in the Day Rule 10b5-1 Plan, between June 12, 2024 and March 13, 2025. The Day Rule 10b5-1 Plan includes a representation from Mr. Day to the broker administering the plan that he was not in possession of any material nonpublic information regarding the Company or the securities subject to the Day Rule 10b5-1 Plan at the time it was entered into. A similar representation was made to the Company in connection with the adoption of the Day Rule 10b5-1 Plan under the Company’s policies regarding transactions in the Company’s securities. Those representations were made as of the date of adoption of the Day Rule 10b5-1 Plan, and speak only as of such date. In making those representations, there is no assurance with respect to any material nonpublic information of which the insider was unaware, or with respect to any material nonpublic information acquired by the insider or the Company after the date of the representation.
Name	Mark J. Day
Title	Chief Technology Officer
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	March 13, 2024
Arrangement Duration	365 days
Aggregate Available	6,090

SUMMARY OF SIGNIFICANT ACCOUN_2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements include the accounts of the Company and its wholly owned subsidiaries, and have been prepared in accordance with generally accepted accounting principles in the United States of America (“GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (the “SEC”) regarding interim financial reporting. As permitted under those rules, the condensed consolidated financial statements and related disclosures as of December 31, 2023 have been derived from the audited consolidated financial statements but do 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 unaudited condensed consolidated financial information. The results of operations for the three months ended March 31, 2024, are not necessarily indicative of the results to be expected for the year ending December 31, 2024, or for any other interim period or for any other future year. The accompanying 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, 2023, included in the Company’s Annual Report on Form 10-K, filed with the SEC on February 22, 2024.
Risks and Uncertainties	Risks and Uncertainties Macroeconomic Factors and Supply Chain Constraints The Company’s operations and performance may vary based on worldwide economic and political conditions, which have been adversely impacted by continued global economic uncertainty, political instability, and military hostilities in multiple geographies including ongoing geopolitical conflicts, such as the war in Ukraine and conflict in the Middle East, domestic and global inflationary trends, interest rate volatility, uncertainty with respect to the federal budget and debt ceiling and potential government shutdowns related thereto, potential instability in the global banking system, global supply shortages, and a tightening labor market. A severe or prolonged economic downturn or period of global political instability could drive hospitals and other healthcare professionals to tighten budgets and curtail spending, which could in turn negatively impact rates at which physicians prescribe the Company’s Zio Services. In addition, higher unemployment rates or reductions in employer-provided benefits plans could result in fewer commercially insured patients, resulting in a reduction in the Company’s margins and impairing the ability of uninsured patients to make timely payments. A weak or declining economy could also strain the Company’s suppliers, possibly resulting in supply delays and disruptions. There is also a risk that one or more of the Company’s current service providers, suppliers, or other partners may not survive such difficult economic times, which could directly affect the Company’s ability to attain its goals on schedule and on budget. If the current equity and credit markets deteriorate, it may make any necessary debt or equity financing more difficult, more costly, and more dilutive. The Company cannot predict the timing, strength, or duration of an economic downturn, instability, or recovery, whether worldwide, in the United States, or within its industry. The Company’s hybrid work arrangements and decision to pursue a sublease for its leased San Francisco headquarters resulted in an impairment of its right-of-use ("ROU") asset and related leasehold improvements and furniture and fixtures during the year ended December 31, 2022. In the fourth quarter of 2023, the Company recorded an additional impairment of its ROU asset and related leasehold improvements and furniture and fixtures related to its leased San Francisco headquarters, due to a continued soft real estate rental market within the city proper San Francisco, California. As the Company continues to evaluate its global real estate footprint, the Company may incur additional impairment charges related to real property lease agreements. The Company is continuously reviewing its liquidity and anticipated capital requirements. The Company believes it has adequate liquidity over the next 12 months to operate its business and to meet its cash requirements. Reimbursement The Company receives revenue for the Zio Services primarily from third-party payors, which include commercial payors and government agencies, such as the Centers for Medicare & Medicaid Services (“CMS”). Third-party payors require the Company to identify the service for which it is seeking reimbursement by using a Current Procedural Terminology (“CPT”) code set maintained by the American Medical Association. These CPT codes are subject to periodic change and update, which will impact the reimbursement rates for the Company’s Zio Services. Based on relative value units, CMS annually updates the reimbursement rates for diagnostic tests performed by IDTFs via the Medicare Physician Fee Schedule. CMS establishes national payment rates for the CPT codes the Company uses to report the long-term Holter monitoring services it performs with its Zio XT System: CPT codes 93247 (for wear-time of greater than 7 days and up to 15 days) and 93243 (for wear-time of greater than 48 hours and up to 7 days). Because remote cardiac monitoring technology, including the Zio System, is rapidly evolving, there is a continuing risk that relative value units assigned, and reimbursement rates set, by CMS may not adequately reflect the value and expense of this technology and associated monitoring services, and CMS may reduce these rates in the future, which would adversely affect the Company’s financial results.
Use of Estimates	Use of Estimates The preparation of the unaudited condensed consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenues and expenses during the periods presented. On an ongoing basis, management evaluates its estimates, including those related to revenue recognition, contractual allowances, allowance for doubtful accounts, the useful lives of property and equipment, the recoverability of long-lived assets, including the estimated usage of the printed circuit board assemblies (“PCBAs”), the incremental borrowing rate for operating leases, accounting for income taxes, impairment of ROU assets, and various inputs used in estimating stock-based compensation. Actual results may differ from those estimates.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash Cash and cash equivalents consist of short-term, highly liquid investments with original maturities of three months or less from the date of purchase. Under the terms of certain facility operating lease agreements, the Company is required to maintain a letter of credit as collateral during the term of the lease. As of March 31, 2024, restricted cash of $8.4 million was pledged as collateral under the letter of credit with Silicon Valley Bank.
Credit 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, U.S. 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.
Inflationary Risk	Inflationary Risk The Company continuously monitors the effects of inflationary factors, such as increases in cost of goods sold and selling and operating expenses, which may adversely affect its results of operations. Specifically, the Company may experience inflationary pressure affecting freight costs, the cost of the components for the Company’s Zio Services, overhead costs relating to maintenance of the Company’s facilities, and in the wages paid to its employees due to challenging labor market conditions. Competitive and regulatory conditions may restrict the Company’s ability to fully recover these costs through price increases. As a result, it may be difficult to fully offset the impact of persistent inflation. The Company’s inability or failure to do so could have a material adverse effect on its business, financial condition and results of operations or cause the Company to need to obtain additional capital earlier than anticipated in the future.
Supply Risk	Supply Risk
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2023, the FASB issued Accounting Standards Update (“ASU”) 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures , which updates reportable segment disclosure requirements primarily through enhanced disclosures about significant segment expenses. The amendments are effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. The Company is currently evaluating this ASU to determine its impact on the Company's consolidated financial statements and related disclosures. In December 2023, the FASB issued ASU No. 2023-09 (“ASU 2023-09”), Income Taxes (Topic 740): Improvement to Income Tax Disclosures to enhance the transparency and decision usefulness of income tax disclosures. Two primary enhancements related to this ASU include disaggregating existing income tax disclosures relating to the effective tax rate reconciliation and income taxes paid. ASU 2023-09 is effective for annual periods beginning after December 15, 2024 on a prospective basis. Early adoption is permitted. The Company is currently evaluating the impact of this accounting standard update on the Company's consolidated financial statements and related disclosures. On March 6, 2024, the SEC adopted SEC Release Nos. 33-11275; 34-99678, The Enhancement and Standardization of Climate-Related Disclosures for Investor , to require the disclosure of certain climate-related information in registration statements and annual reports, including Scope 1 and 2 emissions and information about climate-related risks that have materially impacted, or are reasonably likely to have a material impact on, a company’s business strategy, results of operations, or financial condition. In addition, under the final rules, certain disclosures related to severe weather events and other natural conditions will be required in audited financial statements. The disclosure requirements will begin phasing in for the Company's reports and registration statements including financial information in the fiscal year ending December 31, 2025. On April 4, 2024, the SEC issued an order staying the final rules until the completion of judicial review. The Company is currently evaluating the impact of this final rule on the Company's consolidated financial statements and related disclosures.
Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowances	Accounts Receivable, Allowance for Doubtful Accounts and Contractual Allowances 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 unaudited condensed consolidated balance sheets net of an estimated allowance for doubtful accounts and contractual allowances. The Company establishes an allowance for doubtful accounts for estimated uncollectible receivables based on its assessment of the collectability of customer accounts 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 for services performed. Such provisions are based on the Company's historical experience and are reported as a reduction of revenue. The Company regularly reviews the allowances by considering factors such as historical experience, credit quality, the age of the accounts receivable balances, and current economic conditions that may affect a customer’s ability to pay.
Contract Liabilities	Contract Liabilities ASC 606, Revenue from Contracts with Customers, 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).
Contract Costs	Contract Costs Under ASC 340, Other Assets and Deferred Costs ("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, because the asset that would have resulted from capitalizing these costs will be amortized in one year or less.

REVENUE AND ACCOUNTS RECEIVAB_2

REVENUE AND ACCOUNTS RECEIVABLE (Tables)	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Schedule of Disaggregated Revenue by Payor Type and Major Service	Disaggregated revenue by payor type and major service line for the three months ended March 31, 2024 and 2023 were as follows (in thousands, except percentages): Three Months Ended March 31, 2024 2023 Amount % of Revenue Amount % of Revenue Contracted third-party payors $ 71,773 54% $ 61,907 56% Centers for Medicare and Medicaid 31,786 24% 26,491 24% Healthcare institutions 19,571 15% 15,781 14% Non-contracted third-party payors 8,799 7% 7,257 6% Total $ 131,929 $ 111,436
Schedule of Changes in Allowance for Doubtful Accounts	The following table presents the changes in the allowance for doubtful accounts (in thousands): Three Months Ended Year Ended Three Months Ended Balance, beginning of period $ 20,289 $ 18,475 $ 18,475 Provision for doubtful accounts 6,037 17,105 5,326 Write-offs, net of recoveries and other adjustments (6,337) (15,291) (4,726) Balance, end of period $ 19,989 $ 20,289 $ 19,075
Schedule of Changes in Contractual Allowance	The following table presents the changes in the contractual allowance (in thousands): Three Months Ended Year Ended Three Months Ended Balance, beginning of period $ 52,689 $ 41,389 $ 41,389 Add: provision for contractual adjustments 10,252 52,523 16,099 Less: contractual adjustments (10,870) (41,223) (9,457) Balance, end of period $ 52,071 $ 52,689 $ 48,031

CASH EQUIVALENTS AND MARKETAB_2

CASH EQUIVALENTS AND MARKETABLE SECURITIES (Tables)	3 Months Ended
	Mar. 31, 2024
Cash Equivalents And Investments [Abstract]
Schedule of Cash Equivalents and Marketable Securities	The fair value of cash equivalents and marketable securities as of March 31, 2024 and December 31, 2023, were as follows (in thousands): March 31, 2024 Amortized Gross Unrealized Fair Value Gains Losses Money market funds $ 28,789 $ — $ — $ 28,789 U.S. government securities 48,668 6 (3) 48,671 Total cash equivalents and marketable securities $ 77,457 $ 6 $ (3) $ 77,460 Classified as: Cash equivalents $ 28,789 Marketable securities 48,671 Total cash equivalents and marketable securities $ 77,460 December 31, 2023 Amortized Gross Unrealized Fair Value Gains Losses Money market funds $ 12,594 $ — $ — $ 12,594 U.S. government securities 97,534 59 (2) 97,591 Total cash equivalents and marketable securities $ 110,128 $ 59 $ (2) $ 110,185 Classified as: Cash equivalents $ 12,594 Marketable securities 97,591 Total cash equivalents and marketable securities $ 110,185

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Company's Financial Assets and Liabilities	The following tables present the fair value of the Company’s financial assets determined using the inputs defined above (in thousands): March 31, 2024 Level 1 Level 2 Level 3 Total Assets Money market funds $ 28,789 $ — $ — $ 28,789 U.S. government securities — 48,671 — 48,671 Total $ 28,789 $ 48,671 $ — $ 77,460 December 31, 2023 Level 1 Level 2 Level 3 Total Assets Money market funds $ 12,594 $ — $ — $ 12,594 U.S. government securities — 97,591 — 97,591 Total $ 12,594 $ 97,591 $ — $ 110,185
Schedule of Fair Value of Senior Convertible Notes	The fair value, based on a quoted market price (Level 1), of the Company’s senior convertible notes due 2029 (the "2029 Notes") is as follows (in thousands): March 31, 2024 December 31, 2023 Senior Convertible Notes due 2029 $ 706,215 $ —

BALANCE SHEET DETAILS (Tables)

BALANCE SHEET DETAILS (Tables)	3 Months Ended
	Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Inventory Components	Inventory consisted of the following (in thousands): March 31, 2024 December 31, 2023 Raw materials and work-in-progress $ 6,419 $ 6,299 Finished goods 8,454 7,674 Total $ 14,873 $ 13,973
Schedule of Other Assets	Other assets consisted of the following (in thousands): March 31, 2024 December 31, 2023 PCBAs $ 42,180 $ 38,987 Cloud computing arrangements 6,566 4,959 Strategic investment 3,000 3,000 Other 987 1,093 Total $ 52,733 $ 48,039
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): March 31, 2024 December 31, 2023 Laboratory and manufacturing equipment $ 7,169 $ 6,007 Computer equipment and software 4,035 3,905 Furniture and fixtures 4,180 4,020 Leasehold improvements 27,118 24,885 Internal-use software 64,321 61,980 Internal-use software in development 52,245 43,701 Construction in progress 8,840 10,119 Total property and equipment, gross 167,908 154,617 Less: accumulated depreciation and amortization (55,634) (50,503) Total property and equipment, net $ 112,274 $ 104,114
Schedule of Accrued Liabilities Components	Accrued liabilities consisted of the following (in thousands): March 31, 2024 December 31, 2023 Accrued payroll and related expenses $ 24,995 $ 47,656 Accrued vacation 9,924 8,608 Accrued expenses 19,546 14,891 Claims payable 5,032 4,578 Accrued employee share purchase plan contributions 2,958 1,037 Accrued state and foreign income and sales taxes 2,953 2,877 Accrued professional services fees 4,636 3,715 Total accrued liabilities $ 70,044 $ 83,362

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Schedule of Maturities of Operating Lease Liabilities	Contractual obligations under operating lease liabilities were as follows (in thousands): Year Ended December 31: 2024 (remainder of the year) $ 10,670 2025 15,627 2026 16,090 2027 16,486 2028 16,379 Thereafter 47,098 Total lease payments 122,350 Less: imputed interest (29,421) Total lease liabilities $ 92,929

DEBT (Tables)

DEBT (Tables)	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Schedule of Convertible Debt	The carrying amounts of the Company’s 2029 Notes were as follows (in thousands): March 31, 2024 December 31, 2023 Principal amount $ 661,250 $ — Unamortized debt issuance costs (17,174) — Carrying amount of senior convertible notes due 2029 $ 644,076 $ —
Schedule of Components of Interest Expense and the Effective Interest Rates	The following table summarizes the components of interest expense and the effective interest rate for the 2029 Notes for the periods shown (in thousands): Three Months Ended March 31, 2024 2023 Contractual coupon interest $ 689 $ — Amortized debt issuance costs 399 — Total interest expense recognized on senior convertible notes due 2029 $ 1,088 $ — Effective interest rate 2.0 % — %

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Schedule of Shares of Common Stock for Future Issuance	The Company had reserved shares of common stock for the equity incentive plan issuances as follows (in thousands): March 31, 2024 December 31, 2023 Options issued and outstanding 298 307 Unvested restricted stock units and performance-based restricted stock units 1 2,699 2,438 Shares available for grant under future stock plans 1 6,141 6,765 Shares available for future issuance 9,138 9,510 1 PRSUs are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative Total Shareholder Return ("TSR"), as discussed in Note 11, Equity Incentive Plan and Stock-Based Compensation.

EQUITY INCENTIVE PLAN AND STO_2

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION (Tables)	3 Months Ended
	Mar. 31, 2024
Share-Based Payment Arrangement [Abstract]
Schedule of Share-Based Awards Available for Grant Under 2016 Plan	A summary of awards available for grant under the Company’s 2016 Equity Incentive Plan is as follows (in thousands): Shares Available for Grant Balance as of December 31, 2023 6,765 Awards granted 1 (751) Awards forfeited 1 127 Balance as of March 31, 2024 6,141 1 Awards granted and forfeited include PRSUs, which are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative TSR, as described below .
Schedule of Restricted Stock Units and Performance-Based Restricted Stock Units	The fair value of market based PRSUs were estimated at the date of grant using the Monte-Carlo option pricing model. A summary is as follows (in thousands, except weighted average grant date fair value): Restricted Stock Units Performance Based Restricted Stock Units and Market-Based Units Shares Underlying RSUs Weighted Average Grant Date Fair Value Shares Underlying PRSUs 1 Weighted Average Grant Date Fair Value Balance as of December 31, 2023 1,542 $ 117.90 896 $ 121.80 Granted 503 118.05 248 133.50 Vested (301) 124.95 (62) 77.50 Forfeited (37) 115.01 (90) 85.11 Balance as of March 31, 2024 1,707 $ 116.76 992 $ 130.60 1 Based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on the annual unit volume compound annual growth rate ("CAGR") as described below.
Schedule of Stock Option Activity	The following table summarizes stock option activity: Options Outstanding Options Outstanding (in thousands) Weighted- Weighted- Aggregate Intrinsic Value (in thousands) Balance as of December 31, 2023 307 $ 42.34 3.29 $ 19,859 Options exercised (9) 67.54 Balance as of March 31, 2024 298 41.58 3.13 22,176 Options exercisable – March 31, 2024 298 $ 41.58 3.13 $ 22,176
Schedule of Stock-Based Compensation Expense	The following table summarizes the total stock-based compensation expense included in the unaudited condensed consolidated statements of operations for the three months ended March 31, 2024 and 2023 (in thousands): Three Months Ended March 31, 2024 2023 Cost of revenue $ 846 $ 564 Research and development 3,596 2,387 Selling, general and administrative 16,549 15,300 Total stock-based compensation expense $ 20,991 $ 18,251

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Share	The following table sets forth the computation of the basic and diluted net loss per share during the three months ended March 31, 2024 and 2023 (in thousands, except per share data): Three Months Ended March 31, 2024 2023 Numerator: Net loss $ (45,667) $ (39,109) Denominator: Weighted-average shares used to compute net loss per common share, basic and diluted 31,033 30,297 Net loss per common share, basic and diluted $ (1.47) $ (1.29)
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 three months ended March 31, 2024 and 2023 because their inclusion would be anti-dilutive (in thousands): Three Months Ended March 31, 2024 2023 Options to purchase common stock 298 311 RSUs and PRSUs 1 unvested 2,699 2,523 Senior convertible notes 4,492 — Total 7,489 2,834 1 PRSUs are based on the maximum number of PRSUs in the key executive grant agreements. The actual number of PRSUs awarded will be based on company performance criteria and relative TSR, as discussed in Note 11, Equity Incentive Plan and Stock-Based Compensation.

SUMMARY OF SIGNIFICANT ACCOUN_3

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 8.4
Centers for Medicare and Medicaid | Revenue | Product Concentration Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (as a percent)	24%	24%
Centers for Medicare and Medicaid | Accounts Receivable | Accounts Receivable Concentration Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (as a percent)	24%		25%
One Customer | Accounts Receivable | Accounts Receivable Concentration Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration of credit risk (as a percent)	12%

REVENUE AND ACCOUNTS RECEIVAB_3

REVENUE AND ACCOUNTS RECEIVABLE - Schedule of Disaggregated Revenue by Payor Type and Major Service (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue, net	$ 131,929	$ 111,436
Contracted third-party payors
Disaggregation of Revenue [Line Items]
Revenue, net	$ 71,773	$ 61,907
Contracted third-party payors | Revenue | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration of credit risk (as a percent)	54%	56%
Centers for Medicare and Medicaid
Disaggregation of Revenue [Line Items]
Revenue, net	$ 31,786	$ 26,491
Centers for Medicare and Medicaid | Revenue | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration of credit risk (as a percent)	24%
Healthcare institutions
Disaggregation of Revenue [Line Items]
Revenue, net	$ 19,571	$ 15,781
Healthcare institutions | Revenue | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration of credit risk (as a percent)	15%	14%
Non-contracted third-party payors
Disaggregation of Revenue [Line Items]
Revenue, net	$ 8,799	$ 7,257
Non-contracted third-party payors | Revenue | Product Concentration Risk
Disaggregation of Revenue [Line Items]
Concentration of credit risk (as a percent)	7%	6%

REVENUE AND ACCOUNTS RECEIVAB_4

REVENUE AND ACCOUNTS RECEIVABLE - Schedule of Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Change In The Allowance For Doubtful Accounts
Balance, beginning of period	$ 20,289	$ 18,475	$ 18,475
Provision for doubtful accounts	6,037	5,326	17,105
Write-offs, net of recoveries and other adjustments	(6,337)	(4,726)	(15,291)
Balance, end of period	$ 19,989	$ 19,075	$ 20,289

REVENUE AND ACCOUNTS RECEIVAB_5

REVENUE AND ACCOUNTS RECEIVABLE - Schedule of Changes in Contractual Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Changes In The Contractual Allowance
Balance, beginning of period	$ 52,689	$ 41,389	$ 41,389
Add: provision for contractual adjustments	10,252	16,099	52,523
Less: contractual adjustments	(10,870)	(9,457)	(41,223)
Balance, end of period	$ 52,071	$ 48,031	$ 52,689

REVENUE AND ACCOUNTS RECEIVAB_6

REVENUE AND ACCOUNTS RECEIVABLE - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Contract liability balance, revenue recognized	$ 3,000	$ 2,700
Deferred revenue	$ 3,068		$ 3,306

CASH EQUIVALENTS AND MARKETAB_3

CASH EQUIVALENTS AND MARKETABLE SECURITIES - Schedule of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 77,457	$ 110,128
Gains	6	59
Losses	(3)	(2)
Fair Value	77,460	110,185
Cash Equivalents And Available-for-sale Classified As Investments
Cash equivalents	28,789	12,594
Marketable securities	48,671	97,591
Total cash equivalents and marketable securities	77,460	110,185
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	28,789	12,594
Gains	0	0
Losses	0	0
Fair Value	28,789	12,594
U.S. government securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	48,668	97,534
Gains	6	59
Losses	(3)	(2)
Fair Value	$ 48,671	$ 97,591

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) - USD ($) $ in Thousands	Apr. 30, 2024	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Strategic investment		$ 3,000	$ 3,000
Level 2 | Carrying amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Outstanding interest-bearing obligations			$ 35,000
Subsequent Event
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Strategic investment	$ 10,000

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Fair Value of Company's Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 77,460	$ 110,185
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	28,789	12,594
U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	48,671	97,591
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	28,789	12,594
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	28,789	12,594
Level 1 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	48,671	97,591
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 2 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	48,671	97,591
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	0	0
Level 3 | U.S. government securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial assets	$ 0	$ 0

FAIR VALUE MEASUREMENTS - Sch_2

FAIR VALUE MEASUREMENTS - Schedule of Fair Value of Senior Convertible Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Convertible Notes Due 2029 | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Convertible debt, fair value disclosures	$ 706,215	$ 0

BALANCE SHEET COMPONENTS - Sche

BALANCE SHEET COMPONENTS - Schedule of Inventory Components (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Raw materials and work-in-progress	$ 6,419	$ 6,299
Finished goods	8,454	7,674
Total	$ 14,873	$ 13,973

BALANCE SHEET COMPONENTS - Sc_2

BALANCE SHEET COMPONENTS - Schedule of Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
PCBAs	$ 42,180	$ 38,987
Cloud computing arrangements	6,566	4,959
Strategic investment	3,000	3,000
Other	987	1,093
Total	$ 52,733	$ 48,039

BALANCE SHEET COMPONENTS - Narr

BALANCE SHEET COMPONENTS - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Inventory [Line Items]
Increase in asset purchase	$ 3.2
Printed circuit board assemblies
Inventory [Line Items]
Useful life	1 year
Amortization	$ 2.8	$ 1.4

BALANCE SHEET COMPONENTS - Sc_3

BALANCE SHEET COMPONENTS - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 167,908		$ 154,617
Less: accumulated depreciation and amortization	(55,634)		(50,503)
Total property and equipment, net	112,274		104,114
Depreciation and amortization expense	5,100	$ 3,600
Increase in internal use software	10,900
Laboratory and manufacturing equipment
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	7,169		6,007
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,035		3,905
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	4,180		4,020
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	27,118		24,885
Internal-use software
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	64,321		61,980
Amortization	3,700	$ 2,700
Internal-use software in development
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	52,245		43,701
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment, gross	$ 8,840		$ 10,119

BALANCE SHEET COMPONENTS - Sc_4

BALANCE SHEET COMPONENTS - Schedule of Accrued Liabilities Components (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accrued payroll and related expenses	$ 24,995	$ 47,656
Accrued vacation	9,924	8,608
Accrued expenses	19,546	14,891
Claims payable	5,032	4,578
Accrued employee share purchase plan contributions	2,958	1,037
Accrued state and foreign income and sales taxes	2,953	2,877
Accrued professional services fees	4,636	3,715
Total accrued liabilities	$ 70,044	$ 83,362

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Sep. 03, 2019
Lessee, Lease, Description [Line Items]
Collaboration agreement, additional milestone payments	$ 1,750
Verily Life Sciences LLC
Lessee, Lease, Description [Line Items]
Upfront fee related to development agreement		$ 5,000
Additional aggregate milestone payments related to development agreement		$ 12,750
Collaboration agreement milestone payments	$ 11,000

COMMITMENTS AND CONTINGENCIES_2

COMMITMENTS AND CONTINGENCIES - Schedule of Maturities of Operating Lease Liabilities (Details) $ in Thousands	Mar. 31, 2024 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024 (remainder of the year)	$ 10,670
2025	15,627
2026	16,090
2027	16,486
2028	16,379
Thereafter	47,098
Total lease payments	122,350
Less: imputed interest	(29,421)
Total lease liabilities	$ 92,929

DEBT - Schedule of Convertible

DEBT - Schedule of Convertible Debt (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Mar. 07, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Carrying amount of senior convertible notes due 2029	$ 644,076		$ 0
Convertible Notes Due 2029 | Convertible Debt
Debt Instrument [Line Items]
Principal amount	661,250	$ 661,300	0
Unamortized debt issuance costs	$ (17,174)		$ 0

DEBT - Schedule of Components o

DEBT - Schedule of Components of Interest Expense and the Effective Interest Rates (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Total interest expense recognized on senior convertible notes due 2029	$ 1,088	$ 0
Convertible Notes Due 2029 | Convertible Debt
Debt Instrument [Line Items]
Contractual coupon interest	689	0
Amortized debt issuance costs	$ 399	$ 0
Effective interest rate	2%	0%

DEBT - Narrative (Details)

DEBT - Narrative (Details)					1 Months Ended	3 Months Ended						12 Months Ended
	Mar. 07, 2024 USD ($) $ / shares	Mar. 04, 2024 $ / shares	Jan. 03, 2024 USD ($)	Mar. 28, 2022 USD ($)	Oct. 31, 2018 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2024 USD ($) tradingDay	Mar. 31, 2024 USD ($) consecutiveTradingDay	Mar. 31, 2024 USD ($) businessDay	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of 2029 Notes							$ 661,250,000				$ 0
Debt instrument, capped call transaction, net cost incurred							72,407,000				0
Interest expense, debt							1,088,000					$ 0
Gain (loss) on extinguishment of debt							(7,589,000)				0
Proceeds from issuance of debt							$ 75,000,000				0
Revolving Credit Facility
Debt Instrument [Line Items]
Maximum borrowing capacity				$ 25,000,000
Senior Convertible Notes due 2029 | Convertible Debt
Debt Instrument [Line Items]
Stated interest rate (in percentage)						1.50%	1.50%	1.50%	1.50%	1.50%
Convertible Notes Due 2029 | Braidwell Term Loan Facility
Debt Instrument [Line Items]
Proceeds from issuance of 2029 Notes	$ 80,200,000
Repayment of debt	$ 75,000,000
Interest expense, debt							$ 1,800,000
Convertible Notes Due 2029 | Senior Notes | Braidwell Term Loan Facility
Debt Instrument [Line Items]
Contractual coupon interest							1,600,000
Amortized debt issuance costs							200,000
Convertible Notes Due 2029 | Senior Notes | SVB Term Loan
Debt Instrument [Line Items]
Contractual coupon interest											700,000
Convertible Notes Due 2029 | Convertible Debt
Debt Instrument [Line Items]
Stated interest rate (in percentage)	1.50%
Proceeds from issuance of 2029 Notes	$ 643,600,000
Principal amount	661,300,000					$ 661,250,000	$ 661,250,000	$ 661,250,000	$ 661,250,000	$ 661,250,000		0
Debt instrument, option to purchase convertible debt, additional purchase amount	$ 86,300,000
Debt instrument, convertible, conversion ratio	0.0067927
Debt instrument, convertible, conversion price (in USD per share) | $ / shares	$ 147.22
Debt instrument, covenant repurchase price, percentage						100%	100%	100%	100%	100%
Debt instrument, terms of conversion feature, convertible under certain circumstances, conversion amount						$ 1,000	$ 1,000	$ 1,000	$ 1,000	$ 1,000
Debt instrument, convertible, threshold consecutive trading days								20	30
Debt instrument, terms of conversion feature, convertible regardless of circumstances, conversion amount						$ 1,000	1,000	$ 1,000	$ 1,000	1,000
Debt instrument, redemption covenant, percent of conversion price, last reported sale price of common stock						130%
Debt instrument, redemption price, percentage						100%
Share price | $ / shares	$ 109.05
Contractual coupon interest							689,000					0
Amortized debt issuance costs							399,000					0
Convertible Notes Due 2029 | Convertible Debt | 2029 Capped Call Transactions
Debt Instrument [Line Items]
Debt instrument capped calls, price cap (in USD per share) | $ / shares		$ 218.10
Debt instrument, capped calls premium percentage over closing price		100%
Share price | $ / shares		$ 109.05
Debt instrument, capped call transaction, net cost incurred	$ 72,400,000
Convertible Notes Due 2029 | Convertible Debt | Debt Instrument Conversion Term One
Debt Instrument [Line Items]
Debt instrument, convertible, threshold consecutive trading days								20	30
Debt instrument, convertible, threshold percentage of stock price trigger						130%
Convertible Notes Due 2029 | Convertible Debt | Debt Instrument Conversion Term Two
Debt Instrument [Line Items]
Debt instrument, terms of conversion feature, convertible under certain circumstances, conversion amount						$ 1,000	1,000	$ 1,000	$ 1,000	$ 1,000
Debt instrument, convertible, threshold consecutive trading days | consecutiveTradingDay									5
Debt instrument, convertible, threshold percentage of stock price trigger						98%
Debt instrument, convertible, threshold trading days | businessDay										5
Convertible Notes Due 2029 | Initial Loan | Braidwell Term Loan Facility
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt							5,600,000
Braidwell Term Loan Facility
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 150,000,000
Repayment of debt							78,660,000				0
Braidwell Term Loan Facility | Initial Loan | Secured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity			75,000,000
Braidwell Term Loan Facility | Delayed Draw Loan | Secured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 75,000,000
Debt instrument, access period for delayed draw loan			1 year
Third Amended and Restated SVB Loan Agreement | SVB Term Loan
Debt Instrument [Line Items]
Proceeds from issuance of 2029 Notes			$ 37,800,000
Repayment of debt			$ 35,000,000
Interest expense, debt											$ 800,000
Proceeds from issuance of debt					$ 35,000,000
Amount outstanding under revolving credit line													$ 18,500,000
Third Amended and Restated SVB Loan Agreement | 2022 Term Loan | SVB Term Loan
Debt Instrument [Line Items]
Maximum borrowing capacity				75,000,000
Proceeds from line of credit				35,000,000
Line of credit facility, remaining borrowing capacity												$ 40,000,000
Third Amended and Restated SVB Loan Agreement | 2018 Term Loan | SVB Term Loan
Debt Instrument [Line Items]
Repayment of long-term line of credit				$ 18,500,000
2022 Term Loan | SVB Term Loan
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt							$ 2,000,000

INCOME TAXES (Details)

INCOME TAXES (Details)	Mar. 31, 2024 USD ($)
Income Tax Disclosure [Abstract]
Benefit recognized for net operating loss carryforwards	$ 0

STOCKHOLDERS' EQUITY - Narrativ

STOCKHOLDERS' EQUITY - Narrative (Details) - USD ($)		3 Months Ended
	Mar. 07, 2024	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Common stock, shares authorized (in shares)		100,000,000	100,000,000
Common 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, par value (in USD per share)		$ 0.001	$ 0.001
Dividends declared		$ 0
Convertible Notes Due 2029 | Convertible Debt
Class of Stock [Line Items]
Payments for repurchase of convertible notes	$ 25,000,000
Stock repurchased during period, shares	229,252
Share price	$ 109.05

STOCKHOLDERS' EQUITY - Schedule

STOCKHOLDERS' EQUITY - Schedule of Shares of Common Stock for Future Issuance (Details) - shares shares in Thousands	Mar. 31, 2024	Dec. 31, 2023
Class of Stock [Line Items]
Shares available for future issuance (in shares)	9,138	9,510
Options issued and outstanding
Class of Stock [Line Items]
Shares available for future issuance (in shares)	298	307
Unvested RSUs and PRSUs
Class of Stock [Line Items]
Shares available for future issuance (in shares)	2,699	2,438
Shares available for grant under future stock plans
Class of Stock [Line Items]
Shares available for future issuance (in shares)	6,141	6,765

EQUITY INCENTIVE PLAN AND STO_3

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Schedule of Share-Based Awards Available for Grant Under 2016 Plan (Details) - 2016 Plan shares in Thousands	3 Months Ended
	Mar. 31, 2024 shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Roll Forward]
Beginning balance (in shares)	6,765
Awards granted (in shares)	(751)
Awards forfeited (in shares)	127
Ending balance (in shares)	6,141

EQUITY INCENTIVE PLAN AND STO_4

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Schedule of Restricted Stock Units and Performance-Based Restricted Stock Units (Details) shares in Thousands	3 Months Ended
	Mar. 31, 2024 $ / shares shares
Restricted Stock Units
Shares Underlying RSUs
Beginning balance (in shares) | shares	1,542
Granted (in shares) | shares	503
Vested (in shares) | shares	(301)
Forfeited (in shares) | shares	(37)
Ending balance (in shares) | shares	1,707
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 117.90
Granted (in USD per share) | $ / shares	118.05
Vested (in USD per share) | $ / shares	124.95
Forfeited (in USD per share) | $ / shares	115.01
Ending balance (in USD per share) | $ / shares	$ 116.76
Performance Based Restricted Stock Units and Market-Based Units
Shares Underlying RSUs
Beginning balance (in shares) | shares	896
Granted (in shares) | shares	248
Vested (in shares) | shares	(62)
Forfeited (in shares) | shares	(90)
Ending balance (in shares) | shares	992
Weighted Average Grant Date Fair Value
Beginning balance (in USD per share) | $ / shares	$ 121.80
Granted (in USD per share) | $ / shares	133.50
Vested (in USD per share) | $ / shares	77.50
Forfeited (in USD per share) | $ / shares	85.11
Ending balance (in USD per share) | $ / shares	$ 130.60

EQUITY INCENTIVE PLAN AND STO_5

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended	51 Months Ended
	Feb. 29, 2024	Mar. 31, 2024	Mar. 31, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period (shares)			0
Unvested restricted stock units and performance-based restricted stock units1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to restricted stock unit and performance share		$ 163.5	$ 163.5
Unamortized compensation costs related to unvested stock options, expected period of recognition (in years)		1 year 10 months 24 days
Intrinsic value of equity other than options nonvested		$ 198,100	198,100
Performance Based Restricted Stock Units ("PRSU")
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to restricted stock unit and performance share		$ 54	54
Unamortized compensation costs related to unvested stock options, expected period of recognition (in years)		2 years 2 months 12 days
Intrinsic value of equity other than options nonvested		$ 114,900	$ 114,900
Expected term (in years)	2 years 9 months 18 days
Risk-free interest rate	4.40%
Expected volatility	67.95%
Dividend yield	0%

EQUITY INCENTIVE PLAN AND STO_6

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Options Outstanding (in thousands)
Beginning balance (in shares)	307
Options exercised (in shares)	(9)
Ending balance (in shares)	298	307
Options exercisable (in shares)	298
Weighted- Average Exercise Price Per Share
Beginning balance (in USD per share)	$ 42.34
Options exercised (in USD per share)	67.54
Ending balance (in USD per share)	41.58	$ 42.34
Options exercisable (in USD per share)	$ 41.58
Weighted- Average Remaining Contractual Life (years)
Weighted-average remaining contractual life for options outstanding (in years)	3 years 1 month 17 days	3 years 3 months 14 days
Weighted-average remaining contractual life for options exercisable (in years)	3 years 1 month 17 days
Aggregate Intrinsic Value (in thousands)
Aggregate intrinsic value of options outstanding	$ 22,176	$ 19,859
Aggregate intrinsic value of options exercisable	$ 22,176

EQUITY INCENTIVE PLAN AND STO_7

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Employee Stock Purchase Plan (Details) - ESPP - Employee Stock Purchase Plan $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)
Subsidiary, Sale of Stock [Line Items]
Total unamortized compensation costs, net of estimated forfeitures related to unvested stock options	$ 2,900
Unamortized compensation costs related to unvested stock options, expected period of recognition (in years)	6 months

EQUITY INCENTIVE PLAN AND STO_8

EQUITY INCENTIVE PLAN AND STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 20,991	$ 18,251
Cost of revenue
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	846	564
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	3,596	2,387
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation expense	$ 16,549	$ 15,300

NET LOSS PER SHARE - Schedule o

NET LOSS PER SHARE - Schedule of Computation of Basic and Diluted Net Loss per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net loss	$ (45,667)	$ (39,109)
Denominator:
Weighted-average shares used to compute net loss per common share, basic (in shares)	31,033	30,297
Weighted-average shares used to compute net loss per common share, diluted (in shares)	31,033	30,297
Net loss per common share, basic (in USD per share)	$ (1.47)	$ (1.29)
Net loss per common share, diluted (in USD per share)	$ (1.47)	$ (1.29)

NET LOSS PER SHARE - Schedule_2

NET LOSS PER SHARE - Schedule of Anti-dilutive Securities Excluded from Diluted Net Loss per Common Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	7,489	2,834
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)	298	311
RSUs and PRSUs unvested
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	2,699	2,523
Senior convertible notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from diluted net loss (in shares)	4,492	0