Nevro (NVRO) 10-K 23 Feb 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 16, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Trading Symbol	NVRO
Entity Registrant Name	NEVRO CORP.
Entity Central Index Key	0001444380
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		35,049,108
Entity Public Float			$ 5,695
ICFR Auditor Attestation Flag	true
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, par value $0.001 per share
Security Exchange Name	NYSE
Entity File Number	001-36715
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	56-2568057
Entity Address, Address Line One	1800 Bridge Parkway
Entity Address, City or Town	Redwood City
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94065
City Area Code	650
Local Phone Number	251-0005
Document Annual Report	true
Document Transition Report	false
Documents Incorporated by Reference	Portions of the registrant’s Proxy Statement for the registrant’s 2022 Annual Meeting of Stockholders are incorporated by reference into Part III of this Form 10-K to the extent stated herein. The Proxy Statement will be filed within 120 days of the registrant’s fiscal year ended December 31, 2021.
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	San Jose, California

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 34,710	$ 44,597
Short-term investments	327,317	543,373
Accounts receivable, net of allowance for doubtful accounts of $1,385 and $3,000 at December 31, 2021 and 2020, respectively	70,475	77,667
Inventories	93,517	83,296
Prepaid expenses and other current assets	5,185	4,173
Total current assets	531,204	753,106
Property and equipment, net	20,664	13,531
Operating lease assets	17,577	18,142
Other assets	4,493	4,043
Restricted cash	606	606
Total assets	574,544	789,428
Current liabilities
Accounts payable	31,999	23,109
Accrued liabilities	45,517	43,305
Short-term debt		168,776
Other current liabilities	4,687	3,975
Total current liabilities	82,203	239,165
Long-term debt	151,310	141,771
Long-term operating lease liabilities	15,402	16,689
Other long-term liabilities	22,013	3,343
Total liabilities	270,928	400,968
Commitments and contingencies (Note 7)
Stockholders’ equity
Preferred stock, $0.001 par value, 10,000,000 shares authorized at December 31, 2021 and 2020, respectively; zero shares issued and outstanding at December 31, 2021 and 2020, respectively
Common stock, $0.001 par value, 290,000,000 shares authorized at December 31, 2021 and 2020, respectively; 35,709,570 shares issued and 35,026,654 shares outstanding at December 31, 2021; 34,583,064 shares issued and outstanding at December 31, 2020	35	35
Additional paid-in capital	928,138	880,660
Accumulated other comprehensive income / (loss)	(364)	598
Accumulated deficit	(624,193)	(492,833)
Total stockholders’ equity	303,616	388,460
Total liabilities and stockholders’ equity	$ 574,544	$ 789,428

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 1,385	$ 3,000
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	290,000,000	290,000,000
Common stock, shares issued	35,709,570	34,583,064
Common stock, shares outstanding	35,026,654	34,583,064

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Revenue	$ 386,905	$ 362,048	$ 390,255
Cost of revenue	120,863	112,146	121,905
Gross profit	266,042	249,902	268,350
Operating expenses
Research and development	47,665	45,600	59,017
Sales, general and administrative	309,311	267,154	305,812
Certain litigation charges	20,000
Total operating expenses	376,976	312,754	364,829
Loss from operations	(110,934)	(62,852)	(96,479)
Interest income	671	2,956	6,020
Interest expense	(19,749)	(21,806)	(10,931)
Other income (expense), net	(814)	(495)	(697)
Loss before income taxes	(130,826)	(82,197)	(102,087)
Provision for income taxes	534	868	1,599
Net loss	(131,360)	(83,065)	(103,686)
Other comprehensive loss:
Changes in foreign currency translation adjustment	(469)	991	449
Changes in unrealized gains (losses) on short-term investments, net	(493)	(80)	315
Net change in other comprehensive loss	(962)	911	764
Comprehensive loss	$ (132,322)	$ (82,154)	$ (102,922)
Net loss per share, basic and diluted	$ (3.77)	$ (2.47)	$ (3.37)
Weighted average number of common shares used to compute basic and diluted net loss per share	34,823,258	33,677,641	30,803,872

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balances at Dec. 31, 2018	$ 245,483	$ 30	$ 552,612	$ (306,082)	$ (1,077)
Beginning balances, shares at Dec. 31, 2018		30,263,536
Exercise of common stock options	$ 28,607	$ 1	28,606
Exercise of common stock options, shares	828,722	828,722
Issuance of common stock upon release of restricted stock units		325,839
Shares withheld for tax obligations	$ (3,057)		(3,057)
Shares withheld for tax obligations, shares		(38,696)
Issuance of common stock under employee stock purchase plan	6,545	$ 1	6,544
Issuance of common stock under employee stock purchase plan, shares		164,960
Stock based compensation	41,696		41,696
Net loss	(103,686)			(103,686)
Other comprehensive loss	764				764
Ending balances at Dec. 31, 2019	216,352	$ 32	626,401	(409,768)	(313)
Ending balances, shares at Dec. 31, 2019		31,544,361
Issuance of common stock upon underwritten public offering, net of issuance costs	147,144	$ 2	147,142
Issuance of common stock upon underwritten public offering, net of issuance costs, shares		1,868,750
Conversion feature of convertible senior notes due 2025, net of allocated costs	48,340		48,340
Purchase of bond hedges	(52,390)		(52,390)
Sales of warrants	34,933		34,933
Exercise of common stock options	$ 34,625	$ 1	34,624
Exercise of common stock options, shares	756,797	756,797
Issuance of common stock upon release of restricted stock units		395,971
Shares withheld for tax obligations	$ (8,564)		(8,564)
Shares withheld for tax obligations, shares		(62,782)
Issuance of common stock under employee stock purchase plan	7,513		7,513
Issuance of common stock under employee stock purchase plan, shares		79,967
Stock based compensation	42,661		42,661
Net loss	(83,065)			(83,065)
Other comprehensive loss	911				911
Ending balances at Dec. 31, 2020	388,460	$ 35	880,660	(492,833)	598
Ending balances, shares at Dec. 31, 2020		34,583,064
Exercise of common stock options	$ 4,331		4,331
Exercise of common stock options, shares	90,582	90,582
Issuance of common stock upon release of restricted stock units		346,602
Shares withheld for tax obligations	$ (8,062)		(8,062)
Shares withheld for tax obligations, shares		(58,787)
Issuance of common stock under employee stock purchase plan	6,849		6,849
Issuance of common stock under employee stock purchase plan, shares		65,197
Issuance of common stock from conversion of convertible senior notes due 2021		$ 1	(1)
Issuance of common stock from conversion of convertible senior notes due 2021, shares		682,912
Exercise of bond hedge for convertible senior notes due 2021		$ (1)	1
Exercise of bond hedge for convertible senior notes due 2021, shares		(682,916)
Stock based compensation	44,360		44,360
Net loss	(131,360)			(131,360)
Other comprehensive loss	(962)				(962)
Ending balances at Dec. 31, 2021	$ 303,616	$ 35	$ 928,138	$ (624,193)	$ (364)
Ending balances, shares at Dec. 31, 2021		35,026,654

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net loss	$ (131,360)	$ (83,065)	$ (103,686)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	4,882	4,794	4,563
Amortization of operating lease assets	3,796	3,392	3,237
Stock-based compensation expense	44,367	42,655	41,697
Amortization of premium (accretion of discount) on short-term investments	1,510	320	(2,037)
Provision for (recovery of) doubtful accounts	(1,528)	2,165	(27)
Write-down of inventory	4,257	5,366	1,456
Loss on disposal of equipment		12
Amortization of debt discount and issuance costs	13,263	14,946	7,912
Unrealized gains (losses) on foreign currency transactions	3,083	(184)	(450)
Changes in operating assets and liabilities
Accounts receivable	8,205	3,369	(2,153)
Inventories	(17,225)	2,523	(938)
Prepaid expenses and other current assets	(1,027)	5,666	(3,222)
Other assets	(451)	1,802	514
Accounts payable	9,006	7,678	(7,472)
Accrued liabilities	3,185	(7,897)	13,205
Other long-term liabilities	14,156	(2,351)	(2,824)
Net cash provided by / (used in) operating activities	(41,881)	1,191	(50,225)
Cash flows from investing activities
Purchases of short-term investments	(446,916)	(668,371)	(211,006)
Proceeds from maturity of short-term investments	660,971	297,028	254,308
Repayment from (investment in) private company		7,500	(7,500)
Purchases of property and equipment	(12,340)	(6,025)	(3,472)
Net cash provided by / (used in) investing activities	201,715	(369,868)	32,330
Cash flows from financing activities
Proceeds from issuance of common stock in public offering, net		147,144
Proceeds from issuance of convertible notes		189,750
Convertible notes debt issuance costs		(6,105)
Proceeds from issuance of warrants		34,933
Purchase of convertible note hedges		(52,390)
Repayment of convertible notes	(172,500)
Minimum tax withholding paid on behalf of employees for net share settlement	(8,062)	(8,564)	(3,057)
Proceeds from issuance of common stock to employees	11,181	42,137	35,150
Net cash provided by financing activities	(169,381)	346,905	32,093
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(340)	646	259
Net increase in cash, cash equivalents and restricted cash	(9,887)	(21,126)	14,457
Cash, cash equivalents and restricted cash
Cash, cash equivalents and restricted cash at beginning of year	45,203	66,329	51,872
Cash, cash equivalents and restricted cash at end of year	35,316	45,203	66,329
Supplemental disclosures of cash flow information
Cash paid for income taxes	1,283	1,307	1,338
Cash paid for interest	6,728	5,555	3,019
Significant non-cash transactions
Purchases of property and equipment in accounts payable	$ 526	$ 850	$ 285

Formation and Business of the C

Formation and Business of the Company	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Formation and Business of the Company	1. Formation and Business of the Company The Company was incorporated in Minnesota on March 10, 2006 to manufacture and market innovative active implantable medical devices for the treatment of neurological disorders initially focusing on the treatment of chronic pain. Subsequently, the Company was reincorporated in Delaware on October 4, 2006 and relocated to California. Since inception, the Company has incurred net losses. During the year ended December 31, 2021, the Company incurred a net loss of $131.4 million and had $41.9 million of cash used in operations. At December 31, 2021, the Company had an accumulated deficit of $624.2 million. The Company has financed operations to date primarily through private placements of equity securities, borrowings under a debt agreement, the issuance of common stock in its November 2014 initial public offering, its June 2015 underwritten public offering and its June 2016 underwritten public offering of convertible senior notes due in 2021 (2021 Notes). Additionally, in April 2020, the Company issued a total of $189.8 million aggregate principal amount of convertible senior notes due 2025 (2025 Notes). The total net proceeds from this debt offering, after deducting initial purchase discounts and debt issuance costs, were approximately $183.6 million. Concurrent with this debt offering, the Company also completed an underwritten public offering for 1,868,750 shares of its common stock, from which the Company received cash proceeds of $147.1 million, net of underwriting discounts and commissions and offering costs. The Company’s ability to continue to meet its obligations and to achieve its business objectives for the foreseeable future is dependent upon, amongst other things, generating sufficient revenues and its ability to continue to control expenses to meet its obligations as they become due. Failure to increase sales of its products, manage discretionary expenditures or raise additional financing, if required, may adversely impact the Company’s ability to achieve its intended business objectives. Public Offerings In June 2016, the Company issued $150.0 million aggregate principal amount of 1.75% convertible senior notes due 2021 in a registered underwritten public offering and an additional $22.5 million aggregate principal amount of such notes pursuant to the exercise in full of the over-allotment options of the underwriters (the 2021 Notes). The interest rates are fixed at 1.75% per annum and are payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2016. The total net proceeds from the debt offering, after deducting transaction costs, were approximately $166.2 million. In April 2020, the Company issued $165.0 million aggregate principal amount of 2.75% convertible senior notes due 2025 in a registered underwritten public offering and an additional $24.8 million aggregate principal amount of such notes pursuant to the exercise in full of the over-allotment options of the underwriters (the 2025 Notes). The interest rates are fixed at 2.75% per annum and are payable semi-annually in arrears on April 1 and October 1 of each year, commencing on October 1, 2020. The total net proceeds from the debt offering, after deducting transaction costs, were approximately $183.6 million. Concurrent with the 2025 Notes, the Company completed an underwritten public offering of its common stock and issued 1,868,750 shares of common stock, including 243,750 shares issued pursuant to the exercise in full by the underwriters of their option to purchase additional shares. The Company received cash proceeds of approximately $147.1 million, net of underwriting discounts and commissions and offering costs paid by the Company.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (U.S. GAAP). The consolidated financial statements include the Company’s accounts and those of its five operational wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated. Other Risks and Uncertainties The Company is subject to risks related to the public health crises such as the global pandemic associated with COVID-19, which has spread to most countries and all 50 states within the United States. The COVID-19 outbreak has negatively impacted, and continues to negatively impact, our operations, revenues and overall financial condition and demand for elective procedures remains unpredictable. Additionally, overall patient willingness to pursue elective procedures has decreased due to the pandemic. Although some restrictions on elective procedures have eased, the effect of the pandemic and recent surges in cases continue to affect patient willingness for interventional therapy for chronic pain and the number of elective procedures being performed. These challenges will likely continue for the duration of the pandemic, which is uncertain, and will affect our revenue while the pandemic continues. In addition, the Company is also subject to risks common to medical device companies, including, but not limited to, new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, product liability, manufacturing quality and scaling, continued reimbursement from third-party payors, There can be no assurance that the Company’s products or services will continue to be accepted in its existing marketplaces, nor can there be any assurance that any future products or services can be developed or manufactured at an acceptable cost and with appropriate performance characteristics, or that such products or services will be successfully marketed, if at all. The Company may choose to raise additional funds to further enhance its research and development efforts, for product expansion opportunities or to acquire a new business or products that are complementary to its business. There can be no assurance that such financing will be available or will be at terms acceptable by the Company. Segments The chief operating decision maker for the Company is the Chief Executive Officer. The Chief Executive Officer reviews financial information presented on a consolidated basis, accompanied only by information about revenue by geographic region, for purposes of allocating resources and evaluating financial performance. The Company has one business activity and there are no segment managers who are held accountable for operations, operating results or plans for levels or components below the consolidated unit level, other than revenue. Accordingly, the Company has determined that it has a single reportable and operating segment structure. The Company and its Chief Executive Officer evaluate performance based primarily on revenue in the geographic locations in which the Company operates. Until 2015, the Company had derived most of its revenue from sales to customers in Australia and Europe. In May 2015, the U.S. Food and Drug Administration (FDA) approved the Company’s premarket approval (PMA) application to market Senza in the United States and the Company launched sales in the United States in 2015. Revenue by geography is based on the billing address of the customer. Long-lived assets and operating income outside the United States are not material; therefore, disclosures have been limited to revenue. Foreign Currency Translation The Company’s consolidated financial statements are prepared in U.S. dollars (USD). Its foreign subsidiaries in Europe and Australia use their local currency as their functional currency and maintain their records in the local currency. Accordingly, the assets and liabilities of these subsidiaries are translated into USD using the current exchange rates in effect at the balance sheet date and equity accounts are translated into USD using historical rates. Revenues and expenses are translated using the monthly average exchange rates during the period when the transaction occurs. The resulting foreign currency translation adjustments from this process are recorded in accumulated other comprehensive income (loss) in the consolidated balance sheets. Unrealized foreign exchange gains and losses from the remeasurement of assets and liabilities denominated in currencies other than the functional currency of the reporting entity are recorded in other income (expense), net. The Company recorded net unrealized foreign currency transaction losses of $ 3.3 million during the yea r ended December 31, 20 2 1 , gains of $ million during the year en ded December 31, 20 20 and gains of $ million during the year ended December 31, 201 9 . Additionally, realized gains and losses resulting from transactions denominated in currencies other than the local currency are recorded in other in come (expense), net . The Company recorded realized foreign currency transaction gains of $ 2.6 million during the year ended December 31, 20 2 1 , losses of $ million during the year ended December 31, 20 20 and losses of $ million during the year ended December 31, 201 9 . To the extent that the Company’s international operations grow, the effect of fluctuations in currency rates will become greater, and the Company will continue to reassess its approach to managing this risk. In addition, currency fluctuations or a weakening U.S. dollar can increase the costs of the Company’s international expansion. To date, the Company has not entered into any foreign currency hedging contracts. Based on its current international structure, the Company does not plan on engaging in hedging activities in the near future. Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Significant accounting estimates and management judgments reflected in the consolidated financial statements include items such as allowances for doubtful accounts; warranty obligations; stock-based compensation; depreciation and amortization lives; inventory valuation; valuation of investments; loss contingencies; and accounting for income taxes. Estimates are based on historical experience, where applicable, and other assumptions believed to be reasonable by management. Actual results may differ from those estimates under different assumptions or conditions. Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and investments. The majority of the Company’s cash is held by one financial institution in the United States in excess of federally insured limits. The Company maintained investments in money market funds that were not federally insured during the years ended December 31, 2021 and 2020, and held cash in foreign banks of approximately $8.6 million and $17.6 million at December 31, 2021 and 2020, respectively, that was not federally insured. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s convertible note hedge transactions, entered into in connection with the 2025 Notes, subject the Company to credit risk such that the counterparties may be unable to fulfill the terms of the transactions. The associated risk is mitigated by limiting the counterparties to major financial institutions. In the international markets in which the Company participates, the Company uses both a direct sales force and distributors to sell its products, while in the United States the Company generally utilizes a direct sales force. The Company performs ongoing credit evaluations of some of its direct customers and distributors, does not require collateral, and maintains allowances for potential credit losses on customer accounts when deemed necessary. Credit Losses In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Fair Value of Financial Instruments Carrying amounts of certain of the Company’s financial instruments, including cash equivalents, short term investments, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less at the date of purchase to be cash equivalents. Investment Securities The Company classifies its investment securities as available-for-sale. The Company classifies these investment securities as short-term or long-term based on the nature of the investment, its maturity date and its availability for use in current operations. Those investments with original maturities greater than three months at the date of purchase and remaining maturities of less than 12 months are considered short-term investments. Those investments with remaining maturities greater than 12 months are also classified as short-term investments as management considers them to be available for current operations if needed. The Company’s investment securities are recorded at fair value based on the fair value hierarchy. Money market funds and treasury bonds are classified within Level 1 of the fair value hierarchy, and agency bonds, commercial paper and corporate notes are classified within Level 2 of the fair value hierarchy. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security as an adjustment to yield using the straight-line interest method. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Inventories Inventories are stated at the lower of cost or net realizable value. Cost is determined using the standard cost method which approximates the first-in, first-out basis. Net realizable value is determined as the prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. The Company regularly reviews inventory quantities compared to forecasted sales to record a provision for excess and obsolete inventory when appropriate. The Company estimates forecasted sales by considering product acceptance in the marketplace, customer demand, historical sales, product obsolescence and technological innovations. The Company’s policy is to write down inventory that has become obsolete, inventory that has a cost basis in excess of its expected lower of cost or net realizable value, and inventory in excess of expected requirements. The estimate of excess quantities is judgmental and primarily dependent on the Company’s estimates of future demand for a particular product. If the estimate of future demand is inaccurate based on actual sales, the Company may increase the write-down for excess inventory for that component and record a charge to inventory impairment in the accompanying consolidated statements of operations and comprehensive loss. The Company’s estimation of the future demand for a particular component of the Company’s products may vary and may result in changes in estimates in any particular period. Shipping and Handling Costs Shipping and handling costs are expensed as incurred and are included in cost of revenue. Revenue Recognition The Company has revenue arrangements that generally consist of a single performance obligation, although, in some instances, revenue arrangements may consist of two performance obligations. The Company recognizes revenue at the point in time when it transfers control of promised goods to its customers. Revenue is measured as the amount of consideration it expects to receive in exchange for transferring goods. Revenue is recognized when obligations under the terms of a contract with customers are satisfied, which occurs with the transfer of control of the Company’s goods to its customers. Revenue is measured as the amount of consideration the Company expects to receive in exchange for transferring the goods. For a majority of sales, where the Company’s sales representative delivers its product at the point of implantation at hospitals or medical facilities, the Company recognizes revenue upon completion of the procedure and authorization, which represents the point in time when control transfers to the customers. For the remaining sales, which are sent from the Company’s distribution centers directly to hospitals and medical facilities, as well as distributor sales, where product is ordered in advance of an implantation, the transfer of control occurs at the time of shipment of the product. These customers are obligated to pay within specified terms regardless of when or if they ever sell or use the products. The Company does not offer rights of return or price protection. Sales, value add, and other taxes the Company collects concurrent with revenue-producing activities are excluded from revenue. The expected costs associated with warranty obligations continue to be recognized as expense when the products are sold (see Note 7). The Company periodically provides incentive offers, in the form of rebates, to customers based on their aggregate levels of purchases. Product revenue is recorded net of such incentive offers. Practical Expedients and Exemptions - The Company recognizes revenue upon the transfer of control of the product and there are no material future performance obligations beyond such transfer. As a result, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. The Company does not capitalize incremental costs when the amortization period of the asset is less than a year Allowance for Doubtful Accounts The Company makes estimates of the collectability of accounts receivable and provide an allowance for accounts receivable considered uncollectible based on current expected credit losses. In doing so, the Company analyzes historical bad debt trends, customer concentrations, customer credit worthiness, the age of the receivable, current economic trends and changes in customer payment patterns when evaluating the adequacy of the allowance for doubtful accounts. For the years ended December 31, 2021, 2020 and 2019, the Company recognized bad debt expenses of $0.1 million, $2.8 million and $1.3 million, respectively. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation of property and equipment, other than leasehold improvements, is computed using the straight-line method over the assets’ estimated useful lives of three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful life of the asset or the life of the lease. Upon retirement or sale, the cost and related accumulated depreciation are removed from the consolidated balance sheet and the resulting gain or loss is reflected in operations. Maintenance and repairs are charged to operations as incurred. Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group might not be recoverable. When such an event occurs, management determines whether there has been impairment by comparing the anticipated undiscounted future net cash flows to the related asset group’s carrying value. If an asset is considered impaired, the asset is written down to fair value, which is determined based either on discounted cash flows or appraised value, depending on the nature of the asset. There were no impairment charges, or changes in estimated useful lives , recorded through December 31, 20 2 1 . Lease Accounting The Company has operating leases for office space, warehouse, research and development facilities, manufacturing facilities and equipment. Leases with terms of 12 months or less are not recorded on the balance sheet, as the related lease expenses are recognized on a straight-line basis over the lease term. The Company accounts for lease components (such as fixed payments) separately from nonlease components (such as common area expenses). Operating lease assets and operating lease liabilities are recognized based on the present value of minimum lease payments over the remaining lease term. The Company uses its incremental borrowing rate based on information available when determining the lease liabilities. Lease cost is recognized on a straight-line basis over the expected lease term. Income Taxes The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s consolidated financial statements or income tax returns. In estimating future tax consequences, expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. To date, taxes paid have been predominantly due to income taxes in foreign and state jurisdictions in which we conduct business. The Company provides for tax contingencies whenever it is deemed probable that a tax asset has been impaired or a tax liability has been incurred for events such as tax claims or changes in tax laws. Tax contingencies are based upon their technical merits, relative tax law, and the specific facts and circumstances as of each reporting period. Changes in facts and circumstances could result in material changes to the amounts recorded for such tax contingencies. The Company records uncertain tax positions on the basis of a two-step process whereby (1) a determination is made as to whether it is more likely than not that the tax positions will be sustained based on the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold the Company recognizes the largest amount of tax benefit that is greater than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company’s policy is to recognize interest and penalties related to income taxes as a component of income tax expense. Other Comprehensive Income (Loss) Other comprehensive income (loss) represents all changes in stockholders’ equity except those resulting from distributions to stockholders. The Company’s unrealized gains on short-term available-for-sale investment securities and foreign currency translation adjustments represent the components of other comprehensive income (loss) that are excluded from the reported net loss and are presented in the consolidated statements of operations and comprehensive loss. Research and Development Research and development expenses, including new product development, regulatory compliance, and clinical research, are charged to operations as incurred in the consolidated statements of operations and comprehensive loss. Such costs include personnel-related costs, including stock-based compensation, supplies, services, depreciation, allocated facilities and information services, clinical trial and related clinical manufacturing expenses, fees paid to investigative sites, and other indirect costs. Stock-Based Compensation The Company accounts for stock-based compensation arrangements with employees in accordance with Accounting Standards Codification (ASC) 718, Compensation—Stock Compensation. In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Stock Compensation (Topic 718): Improvements to Employee Shared-Based Payment Accounting The Company’s determination of the fair value of stock options, other than performance-based awards, on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by its common stock price as well as changes in assumptions regarding a number of subjective variables. The expected term that the award will remain outstanding is based on the Company’s own historical data. The expected volatility over the term of the awards is based on the Company’s own common stock volatility and those of its peer group. The risk-free interest rate is based on the U.S. Treasury yield for zero-coupon U.S. Treasury notes with maturities. The expected dividend is zero, as the Company has never paid dividends and has no current plans to do so. The fair value of stock options is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period), on a straight-line basis. Stock-based compensation expense recognized at fair value includes the impact of estimated forfeitures. The Company estimates future forfeitures at the date of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The Company estimates the fair value of the rights to purchase shares by employees under the Employee Stock Purchase Plan using the Black-Scholes option pricing formula. The Employee Stock Purchase Plan provides for consecutive six-month Equity instruments issued to non-employees are recorded at their fair value on the measurement date and are subject to periodic adjustments as the underlying equity instruments vest. The fair value of options granted to consultants is expensed when vested. The non-employee stock-based compensation expense was not material for all periods presented. The Company accounts for stock-based compensation for the restricted stock units at their fair value, based on the closing market price of the Company’s common stock on the grant date. These costs are recognized on a straight-line basis over the requisite service period, which is generally the vesting term of four years. The Company also issues stock options and restricted stock units with vesting based upon achievement of specific operational performance criteria. The fair value for these performance-based awards is recognized over the period during which the goals are to be achieved. Stock-based compensation expense recognized at fair value includes the impact of estimated probability that the goals would be achieved, which is assessed prior to the requisite service period for the specific goals. The Company additionally grants performance stock units with vesting based on its stock price performance compared to a specified target composite index over a certain period. The fair value of these grants is determined by using the Monte Carlo simulation model, which is based on a discounted cash flow approach, and requires inputs such as expected volatility of our stock price, expected volatility of the targeted composite index, correlation between the changes in our stock price and the target composite index, risk-free interest rate and expected dividends. The e xpected volatility of our stock and the target composite index is based on the historical data. Correlation is based on the historical relationship between our stock price and the target composite index . The risk-free interest rate is based upon the treasury yield consistent with the vesting term of the grant. The expected dividend yield is zero . Stock-based compensation for these performance stock units is recognized over the specified performance measurement period . Upon adoption of ASU 2016-09 as described above, excess tax benefits or deficiencies from share-based award activity are reflected in the consolidated statements of operations as a component of the provision for income taxes, whereas they were previously recognized as additional paid-in capital. Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, restricted stock units, common stock options and the conversion spread for the Company’s outstanding convertible senior notes are considered to be potentially dilutive securities. Because the Company has reported a net loss in all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. Recent Accounting Pronouncements Accounting Pronouncements Recently Adopted In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This ASU eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences related to changes in ownership of equity method investments and foreign subsidiaries. The Company adopted ASU 2019-12 on January 1, 2021. The adoption of ASU 2019-12 did not have a material effect on the consolidated financial statements. Accounting Pronouncements Not Yet Effective In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40)

Revenue

Revenue	12 Months Ended
	Dec. 31, 2021
Revenue From Contract With Customer [Abstract]
Revenue	3. Revenue The following table presents revenue by geography, based on the billing address of the customer (in thousands): Years Ended December 31, 2021 2020 2019 United States $ 326,216 $ 311,873 $ 326,012 International 60,689 50,175 64,243 Total revenue $ 386,905 $ 362,048 $ 390,255 The United States is the only country that accounts for 10% or more of the revenue during the periods presented: Years Ended December 31, 2021 2020 2019 United States 84 % 86 % 84 % There were no customers that accounted for 10% 10% In July 2021, the Company received FDA approval of its proprietary 10 kHz Therapy for the management of chronic intractable pain of the lower limbs, including unilateral or bilateral pain, associated with painful diabetic neuropathy (PDN). For the year ended December 31, 2021, worldwide revenue includes approximately $5.7 million of revenue for PDN indication since the July 2021 FDA approval

Leases

Leases	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Leases	4. Leases As of December 31, 2021, the Company has leases with remaining terms of 3 year to 10 years, some of which may include options to extend the lease term for up to 5 years. The weighted average lease terms and discounts rates are as follows: December 31, 2021 2020 Operating Lease Term and Discount Rate Weighted-average remaining lease term 4.20 years 4.32 years Weighted-average discount rate 7.0% 7.0% As of December 31, 2021, t he maturity of lease liabilities are as follows (in thousands): Operating Leases 2022 $ 5,720 2023 6,019 2024 6,201 2025 2,849 2026 405 Thereafter 1,979 Total lease payments 23,173 Less: Interest (3,183 ) Present value of lease liabilities $ 19,990 Supplemental lease cost information are as follows (in thousands): Years Ended December 31, 2021 2020 Operating lease cost $ 5,243 $ 4,936 Supplemental balance sheet information are as follows (in thousands): December 31, 2021 2020 Operating Leases: Operating lease assets $ 17,577 $ 18,142 Other current liabilities $ 4,588 $ 3,876 Long term operating lease liabilities 15,402 16,689 Total operating lease liabilities $ 19,990 $ 20,565 Supplemental cash flow information are as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flow from operating leases $ 5,253 $ 4,923 See Note 7 for further details of the Company’s lease commitments.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurements	5. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or an exit price paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The fair value hierarchy defines a three-level valuation hierarchy for disclosure of fair value measurements as follows: • Level 1 — Observable inputs, such as quoted prices in active markets for identical assets or liabilities. • Level 2 — Observable inputs other than Level 1 prices, such as quoted prices for similar assets or liabilities, quoted prices in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. • Level 3 — Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. Cash Equivalents and Short Term Investments The Company’s cash equivalents include investments in money market funds that which are unrestricted as to withdrawal or use and are classified as Level 1 of the fair value hierarchy. To value its money market funds, the Company values the funds at $1 stable net asset value, which is the quoted price in active markets for identical assets that the Company has the ability to access. At December 31, 2021 and 2020, the Company’s cash equivalents were held in institutions in the United States. The Company’s cash equivalents and short-term investments also includes agency bonds, commercial paper, corporate notes and treasury bonds, which have been classified within Level 1 or Level 2 of the fair value hierarchy because of the sufficient observable inputs for revaluation. The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of any broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs. The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis, by level, within the fair value hierarchy (in thousands): Balance as of December 31, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds (i) $ 9,562 $ — $ — $ 9,562 Agency bonds (ii) — 42,538 — 42,538 Commercial paper (ii) — 61,884 — 61,884 Corporate notes (iii) — 30,351 — 30,351 Treasury bonds (ii) 197,552 — — 197,552 Total assets $ 207,114 $ 134,773 $ — $ 341,887 Balance as of December 31, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds (i) $ 16,273 $ — $ — $ 16,273 Agency bonds (ii) — 210,302 — 210,302 Commercial paper (ii) — 277,602 — 277,602 Corporate notes (ii) — 25,395 — 25,395 Treasury bonds (ii) 30,074 — — 30,074 Total assets $ 46,347 $ 513,299 $ — $ 559,646 (i) Included in cash and cash equivalents on the consolidated balance sheets. (ii) Included in short-term investments on the consolidated balance sheets. (iii) Included in either cash and cash equivalents or short-term investments on the consolidated balance sheets. Convertible Senior Notes On June 1, 2021, the Company settled the 2021 Notes at maturity, and as of December 31, 2021, the 2021 Notes were no longer outstanding. As of December 31, 2020, the fair value of the 1.75% convertible senior notes due 2021 was $312.8 million. As of December 31, 2021 and 2020, the fair value of the 2.75% convertible senior notes due 2025 was $212.0 million and $348.1 million, respectively. The fair value was determined on the basis of market prices observable for similar instruments and is considered Level 2 in the fair value hierarchy.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	6. Balance Sheet Components Investments The fair value of the Company’s cash equivalents and short-term investments approximates their respective carrying amounts due to their short-term maturity. The following is a summary of the gross unrealized gains and unrealized losses on the Company’s investment securities (in thousands): December 31, 2021 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value Investment Securities Agency bonds $ 42,546 $ — $ (8 ) $ 42,538 Commercial paper 61,886 2 (4 ) 61,884 Corporate notes 30,371 — (20 ) 30,351 Treasury bonds 197,889 2 (339 ) 197,552 Total securities $ 332,692 $ 4 $ (371 ) $ 332,325 December 31, 2020 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value Investment Securities Agency bonds $ 210,225 $ 79 $ (2 ) $ 210,302 Commercial paper 277,593 23 (14 ) 277,602 Corporate notes 25,364 40 (9 ) 25,395 Treasury bonds 30,064 10 — 30,074 Total securities $ 543,246 $ 152 $ (25 ) $ 543,373 Realized gains or losses from the sale of investments and other-than-temporary impairments, if any, on available-for-sale securities are reported in other income (expense), net as incurred. The cost of securities sold was determined based on the specific identification method. The amount of realized gains and realized losses on investments for the periods presented have not been material. The amortized costs and estimated fair values of the Company’s available-for-sale securities by contractual maturities as of December 31, 2021 were as follows (in thousands): Amortized Cost Fair Value Amounts maturing within one year $ 305,844 $ 305,535 Amounts after one year through five years 26,848 26,790 Total investment securities $ 332,692 $ 332,325 Inventories (in thousands) December 31, 2021 2020 Raw materials $ 50,160 $ 34,405 Finished goods 43,357 48,891 Total inventories $ 93,517 $ 83,296 The Company periodically evaluates the carrying value of inventory on hand for potential excess amount over demand using the same lower of cost or net realizable value approach as that has been used to value the inventory. The Company also periodically evaluates inventory quantities in consideration of actual loss experience. As a result of these evaluations, for the year ended December 31, 2021, the Company recognized total write-downs of $ 4.3 million for its inventories. For the years ended December 31, 2020 and 2019, the Company recognized total write-downs of $ 5.4 million and $ 1.6 million, respectively, for its inventories. Property and Equipment, Net (in thousands) December 31, 2021 2020 Laboratory equipment $ 8,722 $ 7,072 Computer equipment and software 16,349 12,671 Furniture and fixtures 4,215 3,918 Leasehold improvements 10,316 4,289 Construction in process 3,717 3,354 Total 43,319 31,304 Less: Accumulated depreciation and amortization (22,655 ) (17,773 ) Property and equipment, net $ 20,664 $ 13,531 Depreciation and amortization expense for the years ended December 31, 2021, 2020 and 2019 was $4.9 million, $4.8 million and $4.6 million, respectively. Restricted Cash Restricted cash as of December 31, 2021 and 2020 includes certificates of deposit of $0.6 million representing collateral for the Company’s Redwood City, CA building lease pursuant to an agreement dated March 5, 2015. Accrued Liabilities (in thousands) December 31, 2021 2020 Accrued payroll and related expenses $ 30,957 $ 30,971 Accrued professional fees 6,547 2,101 Accrued taxes 1,074 1,191 Accrued clinical and research expenses 305 668 Accrued interest 1,305 1,548 Accrued warranty 664 699 Accrued other 4,665 6,127 Total accrued liabilities $ 45,517 $ 43,305

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Leases In March 2015, the Company entered into a lease agreement for approximately 50,740 square feet of office space located in Redwood City, California for a period beginning in June 2015 The lease for the Expansion Premises commenced on June 1, 2018. In February 2017, the Company entered into a separate non-cancellable facility lease for warehouse space beginning March 1, 2017 through February 28, 2022, under which the Company is obligated to pay approximately $0.4 million in lease payments over the term of the lease. In October 2021, the Company entered into an amendment to extend the lease term to May 31, 2025. In August 2020, the Company entered into a lease for approximately 35,411 square feet of space for a manufacturing facility in Costa Rica for a period of April 2021 See Note 4 for further discussion on Leases. Warranty Obligations The Company warrants that its products will operate substantially in conformity with product specifications and provides a limited one- to five-year warranty. Activities related to warranty obligations were as follows (in thousands): December 31, 2021 2020 Beginning Balance $ 699 $ 1,178 Provision for warranty 2,846 2,150 Utilization (2,881 ) (2,629 ) Ending Balance $ 664 $ 699 Supply Agreements The Company has entered into supply agreements with certain of the Company’s suppliers that required certain minimum annual purchase agreements. As of December 31, 2021, the Company had $0.9 million of annual purchase commitments. As of December 31, 2020, the Company had no annual purchase commitments. For the year ended December 31, 2019, the Company recorded a charge of $3.6 million related to the cancellation of firm purchase commitments for inventory related items. The Company also entered into a service agreement in January 2020 for which it is committed to pay $ 2.5 million License Agreements In March 2006, the Company entered into an amended and restated license agreement with the Mayo Foundation for Medical Education and Research (Mayo) and Venturi Group LLC (VGL), which provides the Company access to the certain know how and licensed patents owned by Mayo and VGL for treatment of central, autonomic and peripheral nervous system disorders, including pain, using devices to modulate nerve signaling. The licenses granted are exclusive and the Company has the right to sub-license. The agreement will terminate upon the last to expire patent application, unless terminated earlier. The agreement can be terminated any time after three years from March 2006 by Mayo or VGL. Per terms of the license, the Company is required to pay royalties based on the greater of earned royalty or minimum royalty. The earned royalty will be based on a percentage of net sales of licensed products either by the Company or the sub-licensee. The minimum royalty payment will be based on royalty periods as defined in the agreement. In March 2011, the Company entered into a Phase II License Agreement with Mayo which provides the Company access to the certain know how and licensed patents owned by Mayo. The licenses granted are exclusive and the Company has the right to sub-license. The agreement will terminate upon the last to expire patent application, unless terminated earlier. Per terms of the license, the Company is required to: • Pay a retainer fee of $40,000 per annum starting March 2011 and ending February 2013; • Pay royalties based on the greater of earned royalty or minimum royalty. The earned royalty is based on a percentage of net sales of licensed products either by the Company or the sub-licensee. The minimum annual royalty payment is $200,000. The Mayo License terminates upon the expiration of (1) the last to expire of the licensed patents or (2) our obligation to pay royalties, whichever is later. Such obligations may be subject to change if: (1) additional relevant patents issue that are subject to the Mayo License; or (2) we launch an SCS product, which is subject to the Mayo License, in another country. As of Jan. 1, 2021, the Company does not have an existing obligation to pay royalties under the Mayo License. Therefore, there were no royalties expenses during the year ended December 31, 2021. Royalties expenses during the years ended December 31, 2020 and 2019 were $3.1 million and $3.2 million, respectively. In November 2014, the Company issued Mayo 20,833 shares of common stock owed in connection with the IPO pursuant to the terms of the license, and recorded noncash research and development expense of $0.5 million for the fair value of the shares on the date of issuance. In July 2017, the Company entered into a license agreement for which it is committed to pay $0.1 million over the remaining term of this license agreement, which ends in 2022. Contingent Consideration In February 2019, the Company entered into an agreement with a privately-held company to, among other things, provide the privately-held company financing in the form of a secured convertible note. Through March 31, 2020, the Company has provided financing totaling $8.5 million in the form of two secured convertible notes. The agreement additionally provides the Company with the exclusive right, but not the obligation, to acquire the privately-held company. As of December 31, 2019, the value of the secured convertible notes, measured at amortized cost, was $7.9 million, while the value of certain rights in relation to the agreement, measured at cost and monitored for impairment on an ongoing basis, was $1.0 million. These amounts are reported in Other Assets on the Condensed Consolidated Balance Sheet. The accretion of amortized cost is recorded in Interest Income, while any changes in value from impairment assessment are recorded in Other Income (Expense) in the Consolidated Statements of Operations and Comprehensive Income. The Company concluded that the privately-held company is a variable interest entity; however, the Company is not the primary beneficiary as it does not retain power to direct the activities that most significantly impact its economic performance. In April 2020, the Company elected not to exercise its option to make a further investment in the privately-held company pursuant to the agreement. In connection with this decision, the Company no longer has the exclusive right to acquire the privately-held company. In June 2020, the privately-held company paid off the outstanding principal and accrued interest of its secured convertible notes in full. As a result of these two events, the Company recorded a net expense of $0.4 million in Other Income (Expense) in the Consolidated Statements of Operations and Comprehensive Income in the year ended December 31, 2020. Contingencies From time to time, the Company may have certain contingent liabilities that arise in the ordinary course of business activities. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. There have been no contingent liabilities requiring accrual at December 31, 2021 and 2020. Indemnification The Company enters into standard indemnification arrangements in the ordinary course of business. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, including, among other circumstances, in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third-party with respect to the Company’s technology. The term of these indemnification agreements is generally perpetual. The maximum potential amount of future payments the Company could be required to make under these agreements is not determinable because it involves claims that may be made against the Company in the future, but have not yet been made. The Company has 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, other than liabilities arising from willful misconduct of the individual. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited; however, the Company has director and officer insurance coverage that reduces the Company’s exposure and enables the Company to recover a portion of any future amounts paid. The Company believes the estimated fair value of these indemnification agreements in excess of applicable insurance coverage is minimal. The Company has not incurred costs to defend lawsuits or settle claims related to these indemnification agreements. No liability associated with such indemnifications has been recorded to date. Legal Matters Boston Scientific Litigations California Litigation Related to High Frequency On November 28, 2016, the Company filed a lawsuit for patent infringement against Boston Scientific Corporation and Boston Scientific Neuromodulation Corporation (collectively, Boston Scientific). The lawsuit, filed in the U.S. District Court for the Northern District of California (the California Court), asserted that Boston Scientific was infringing, or would soon begin infringing, seven of the Company’s patents covering inventions relating to the Senza system and 10 kHz Therapy. Shortly after the Company filed this lawsuit in 2016, Boston Scientific cancelled its original launch plan and modified its SCS system to avoid infringing the asserted patents. On July 24, 2018, the California Court issued an order on claim construction and summary judgment. In the order, the California Court ruled that the Company’s asserted method claims were patent eligible and not invalid as indefinite. Collectively, the asserted method claims cover methods for delivering SCS therapy at frequencies between 1.5 kHz and 100 kHz. The California Court, however, found that Boston Scientific was not currently infringing the six upheld method claims because Boston Scientific cancelled its original launch plans and ultimately never practiced the asserted method claims in the United States. Specifically, the California Court found that Boston Scientific's sale of the Spectra WaveWriter systems for commercial use in the United States did not infringe the upheld method claims because Boston Scientific modified the Spectra WaveWriter systems to prevent them from being programmed to generate signals above 1.2 kHz. The California Court also found that the Company’s asserted system claims were invalid as indefinite. As discussed below, the California Court’s finding of invalidity was overturned by the U.S. Court of Appeals for the Federal Circuit (the Federal Circuit). On July 31, 2018, the parties entered into an agreement to dismiss the Company’s declaratory judgment claims, without prejudice, so that the Company and Boston Scientific could each appeal portions of the California Court’s July 24th ruling to the Federal Circuit. On April 9, 2020, the Federal Circuit returned its ruling, which vacated and remanded the California Court’s judgment of invalidity. As a result of the Federal Circuit’s ruling, the system claims invalidated by the California Court were reinstated, and thus all of the Company’s asserted claims remain valid and enforceable. On December 14, 2020, the parties agreed to the final dismissal of all remaining claims before the California Court based on Boston Scientific’s assertion to the court that it did not have any current plans to commercially launch a high frequency SCS system in the United States. The California Court entered the agreed upon dismissal on December 16, 2020. Delaware Litigations Unrelated to High Frequency On December 9, 2016, Boston Scientific filed a patent infringement lawsuit alleging the Company’s manufacture, use and sale of the Senza system infringes ten of Boston Scientific’s patents covering spinal cord stimulation technology related to stimulation leads, rechargeable batteries and telemetry (the Delaware I Delaware II In relation to the Delaware I inter partes Delaware II inter partes inter partes Through various orders from the court, portions of Boston Scientific’s Delaware I Delaware II In relation to the Delaware I Delaware I In relation to the Delaware II inter partes On February 23, 2021, the Company filed a patent infringement lawsuit against Boston Scientific alleging that its January 2021 launch of the WaveWriter Alpha™ SCS System infringes five of the Company’s patents covering spinal cord stimulation technology related to delivering paresthesia-free therapy at frequencies below 1,200 Hz. The lawsuit, filed in the U.S. District Court for the District of Delaware ( the Delaware III As of December 31, 2021, the Company recorded a liability of $20.0 million in relation to the aforementioned Delaware I case Stimwave Litigation On February 14, 2019, the Company filed a lawsuit for patent infringement against Stimwave Technologies, Inc. (Stimwave) in the Delaware Court asserting that Stimwave was infringing the Company’s patents covering inventions related to its 10 kHz Therapy and the Senza system, as well as a claim for false advertising under the Lanham Action Section 43(a), 15 U.S.C. § 1125(a). In relation to this lawsuit, on July 24, 2019, the Delaware Court granted the Company’s motion for preliminary injunction, and issued an order barring Stimwave, and all affiliated persons and entities, from infringing patent claims covering frequencies between 3 kHz and 10 kHz. On February 27, 2020, the Company and Stimwave entered into a Settlement Agreement, in which Stimwave agreed to cease commercialization of all high frequency spinal cord stimulation systems worldwide. Stimwave also agreed to entry of a permanent injunction in the Delaware Court, under which Stimwave’s products will not deliver spinal cord stimulation therapy that includes pulse frequencies between 1,500 Hz and 100,000 Hz. The permanent injunction w as filed with the Delaware C ourt and entered on March 2, 2020 . A fter the Delaware C ourt enter ed the permanent injunction, the case (including Stimwave’s appeal of the preliminary injunction order) were dismissed. As part of the permanent injunction filing, Stimwave acknowledge d the validity of the patents Nevro asserted in the litigation. Per the Company’s request, the permanent injunction order does not enjoin Stimwave from providing follow-up care and programming for any patients who were already programmed with high frequency therapy in the United States prior to March 6, 2020, and in the rest of the world prior to April 30, 2020 . Nalu Litigation On February 28, 2020, the Company filed a lawsuit in the Delaware Court for patent infringement against Nalu Medical, Inc. (Nalu) asserting that Nalu is infringing the Company’s patents covering inventions related to its 10 kHz Therapy and the Senza system. The Company is and may from time to time continue to be involved in various legal proceedings to defend its intellectual property, including several pending European patent oppositions at the European Patent Office (EPO) initiated by the Company’s competitors Medtronic and Boston Scientific, an entitlement action filed by Boston Scientific in Germany, and an invalidity proceeding in China. In addition, the Company is and may from time to time also be involved in various legal proceedings of a character normally incident to the ordinary course of business, such as employment matters, product liability matters, and professional liability matters, which the Company does not deem to be material to its business and condensed consolidated financial statements at this stage.

Long-term Debt

Long-term Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Long-term Debt	8. Long-term Debt 2021 Notes and Convertible Note Hedge and Warrant Transactions In June 2016, the Company issued $150.0 million aggregate principal amount of 1.75% convertible senior notes due in June 2021 in a registered underwritten public offering and an additional $22.5 million aggregate principal amount of such notes pursuant to the exercise in full of the over-allotment options of the underwriters (the 2021 Notes). The interest rates are fixed at 1.75% per annum and are payable semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2016. The total net proceeds from the debt offering, after deducting initial purchase discounts and debt issuance costs, were approximately $166.2 million. Each $1,000 principal amount of the 2021 Notes will initially be convertible into 10.3770 shares of the Company’s common stock, which is equivalent to an initial conversion price of approximately $96.37 per share, subject to adjustment upon the occurrence of specified events. The 2021 Notes will be convertible at the option of the holders at any time prior to the close of business on the business day immediately preceding December 1, 2020, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on September 30, 2016 (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 on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period (the measurement period) in which the trading price (as defined in the indenture to the 2021 Notes) per $1,000 principal amount of notes for each trading day of the 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 on each such trading day; or (3) upon the occurrence of specified corporate events. On or after December 1, 2020 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their 2021 Notes at any time, regardless of the foregoing circumstances. Upon conversion, the Company will pay or deliver, as the case may be, cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock, at the Company’s election. If the Company undergoes a fundamental change prior to the maturity date, holders of the notes may require the Company to repurchase for cash all or any portion of their notes at a repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In addition, if specific corporate events occur prior to the applicable maturity date, the Company will increase the conversion rate for a holder who elects to convert their notes in connection with such a corporate event in certain circumstances. In connection with the offering of the 2021 Notes, the Company entered into convertible note hedge transactions with certain bank counterparties in which the Company has the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 1.8 million shares of the Company’s common stock at a price of approximately $96.37 per share. The total cost of the convertible note hedge transactions was $45.1 million. In addition, the Company sold warrants to certain bank counterparties whereby the holders of the warrants have the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 1.8 million shares of the Company’s common stock at a price of $127.28 per share. The Company received $33.1 million in cash proceeds from the sale of these warrants. Taken together, the purchase of the convertible note hedges and the sale of warrants are intended to offset any actual dilution from the conversion of these notes and to effectively increase the overall conversion price from $96.37 to $127.28 per share. As these transactions meet certain accounting criteria, the convertible note hedges and warrants are recorded in stockholders’ equity and are not accounted for as derivatives. The net cost of $12.0 million incurred in connection with the convertible note hedge and warrant transactions was recorded as a reduction to additional paid-in capital on the consolidated balance sheet. In accounting for the issuance of the convertible senior notes, the Company separated the 2021 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was $32.9 million and was determined by deducting the fair value of the liability component from the par value of the 2021 Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The excess of the principal amount of the liability component over its carrying amount (debt discount) is amortized to interest expense over the term of the 2021 Notes expense at an effective interest rate of 6.29% over the contractual terms of the notes. In accounting for the debt issuance costs of $6.2 million related to the 2021 Notes, the Company allocated the total amount incurred to the liability and equity components of the 2021 Notes based on their relative values. Issuance costs attributable to the liability component were $5.0 million and will be amortized to interest expense using the effective interest method over the contractual terms of the 2021 Notes. Issuance costs attributable to the equity component were netted with the equity component in stockholders’ equity. On June 1, 2021, the 2021 Notes matured and the Company settled the 2021 Notes. The Company paid $172.5 million to settle the outstanding principal and issued 682,912 shares of common stock to holders who elected to convert the 2021 Notes. In addition, the Company exercised its option under the bond hedge and received 682,916 shares of common stock from the bank counterparties. None of the holders of the warrants associated with the 2021 Notes exercised the option to purchase shares. As of December 31, 2021, the 2021 Notes were no longer outstanding. The net carrying amount of the liability component of the 2021 Notes was as follows (in thousands): December 31, 2020 Principal $ 172,500 Unamortized discount (3,182 ) Unamortized issuance cost (542 ) Net carrying amount $ 168,776 The net carrying amount of the equity component of the 2021 Notes was as follows (in thousands): December 31, 2020 Debt discount related to value of conversion option $ 32,945 Debt issuance cost (1,179 ) Net carrying amount $ 31,766 2025 Notes and Convertible Note Hedge and Warrant Transactions In April 2020, the Company issued $165.0 million aggregate principal amount of 2.75% convertible senior notes due 2025 in a registered underwritten public offering and an additional $24.8 million aggregate principal amount of such notes pursuant to underwriters’ exercise in full of their option to purchase additional 2025 Notes. The interest rates are fixed at 2.75% per annum and are payable semi-annually in arrears on April 1 and October 1 of each year, commencing on October 1, 2020. The total net proceeds from the debt offering, after deducting initial purchase discounts and debt issuance costs, were approximately $183.6 million. Each $1,000 principal amount of the 2025 Notes will initially be convertible into 9.5238 shares of the Company’s common stock, which is equivalent to an initial conversion price of approximately $105.00 per share, subject to adjustment upon the occurrence of specified events. The 2025 Notes will be convertible at the option of the holders at any time prior to the close of business on the business day immediately preceding October 1, 2024, only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2020 (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 on each applicable trading day; (2) during the five business day period after any ten consecutive trading day period (the measurement period) in which the trading price (as defined in the indenture to the 2025 Notes) per $1,000 principal amount of notes for each trading day of the 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 on each such trading day; or (3) upon the occurrence of specified corporate events. On or after October 1, 2024 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their 2025 Notes at any time, regardless of the foregoing circumstances. If the Company undergoes a fundamental change prior to the maturity date, holders of the notes may require the Company to repurchase for cash all or any portion of their notes at a repurchase price equal to 100% of the principal amount of the notes to be repurchased, plus accrued and unpaid interest to, but excluding, the fundamental change repurchase date. In connection with the offering of the 2025 Notes, the Company entered into convertible note hedge transactions with certain bank counterparties in which the Company has the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 1.8 million shares of the Company’s common stock at a price of approximately $105.00 per share. The total cost of the convertible note hedge transactions was $52.4 million. In addition, the Company sold warrants to certain bank counterparties whereby the holders of the warrants have the option to purchase initially (subject to adjustment for certain specified events) a total of approximately 1.8 million shares of the Company’s common stock at a price of $147.00 per share. The Company received $34.9 million in cash proceeds from the sale of these warrants. Taken together, the purchase of the convertible note hedges and the sale of warrants are intended to offset any actual dilution from the conversion of these notes and to effectively increase the overall conversion price from $105.00 to $147.00 per share. As these transactions meet certain accounting criteria, the convertible note hedges and warrants are recorded in stockholders’ equity and will not be subsequently remeasured as long as they continue to meet the conditions for equity classification. The net cost of $ 17.5 million incurred in connection with the convertible note hedge and warrant transactions was recorded as a reduction to additional paid-in capital on the consolidated balance sheet. In accounting for the issuance of the convertible senior notes, the Company separated the 2025 Notes into liability and equity components. The carrying amount of the liability component was calculated by measuring the fair value of a similar debt instrument that does not have an associated convertible feature. The carrying amount of the equity component representing the conversion option was $49.9 million and was determined by deducting the fair value of the liability component from the par value of the 2025 Notes. The equity component is not remeasured as long as it continues to meet the conditions for equity classification. The excess of the principal amount of the liability component over its carrying amount (debt discount) is amortized to interest expense over the term of the 2025 Notes expense at an effective interest rate of 10.2% over the contractual terms of the notes. In accounting for the debt issuance costs of $6.1 million related to the 2025 Notes, the Company allocated the total amount incurred to the liability and equity components of the 2025 Notes based on the same proportion as the accounting for the proceeds from the issuance of the 2025 Notes. Issuance costs attributable to the liability component were $4.5 million and will be amortized to interest expense using the effective interest method over the contractual terms of the 2025 Notes. The net carrying amount of the liability component of the 2025 Notes was as follows (in thousands): December 31, 2021 2020 Principal $ 189,750 $ 189,750 Unamortized discount (35,079 ) (43,919 ) Unamortized issuance cost (3,361 ) (4,060 ) Net carrying amount $ 151,310 $ 141,771 The net carrying amount of the equity component of the 2025 Notes was as follows (in thousands): December 31, 2021 2020 Debt discount related to value of conversion option $ 49,947 $ 49,947 Debt issuance cost (1,607 ) (1,607 ) Net carrying amount $ 48,340 $ 48,340 The following table sets forth the interest expense recognized related to the 2021 Notes and 2025 Notes (in thousands): Years Ended December 31, 2021 2020 2019 Contractual interest expense $ 6,484 $ 6,860 $ 3,019 Amortization of debt discount 12,023 13,308 6,843 Amortization of debt issuance costs 1,240 1,634 1,063 Total interest expense $ 19,747 $ 21,802 $ 10,925

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Convertible Preferred Stock	9. Convertible Preferred Stock Prior to its initial public offering, the Company had outstanding 15,208,048 shares of convertible preferred stock. Each share of preferred stock was convertible to one share of common stock. Upon the closing of the Company’s initial public offering on November 11, 2014, all shares of outstanding redeemable convertible preferred stock were automatically converted to 15,208,048 shares of the Company’s common stock.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stock-Based Compensation	10. Stock-Based Compensation Common stock reserved for future issuance as of December 31, 2021 was as follows: Shares Outstanding stock options and awards 1,713,145 Reserved for grants of future stock options and awards 6,078,869 Reserved for employee stock purchase plan 1,567,514 Total common stock reserved for future issuance 9,359,528 Stock Plans The Company’s Board of Directors (Board) and stockholders previously approved the 2007 Stock Option Plan (the 2007 Plan). In October 2014, the Board adopted the 2014 Equity Incentive Award Plan (the 2014 Plan and, together with the 2007 Plan, the Stock Plans). As of the effective date of the 2014 Plan, the Company suspended the 2007 Plan and no additional awards may be granted under the 2007 Plan. Any shares of common stock covered by awards granted under the 2007 Plan that terminate after the effective date of the 2014 Plan by expiration, forfeiture, cancellation or other means without the issuance of such shares, will be added to the 2014 Plan reserve. Under the 2014 Plan, 1,854,166 shares of common stock were initially reserved for issuance, plus the number of shares remaining available for future awards under the 2007 Plan, as of the pricing of the IPO. The number of shares initially reserved for issuance under the 2014 Plan is subject to increase by (i) the number of shares represented by awards outstanding under the 2007 Plan that are forfeited or lapse unexercised and which following the pricing date are not issued under the 2007 Plan, and (ii) an annual increase on January 1 of each year. Under the 2014 Plan, the Company may grant awards such as incentive stock options, nonstatutory stock options, restricted stock units, performance stock units and stock appreciation rights. Incentive stock options (ISO) may be granted only to Company employees (including directors who are also employees). Nonqualified stock options (NSO) may be granted to Company employees, directors and consultants. Stock Options Options under the 2014 Plan may be granted for periods of up to ten years and at prices no less than 100% of the estimated fair market value of the shares on the date of grant as determined by the Board, provided, however, that the exercise price of an ISO or an NSO granted to a 10% stockholder shall not be less than 110% of the estimated fair market value of the shares on the date of grant. Upon the exercise of options, the Company issues new common stock from its authorized shares. The vesting provisions of individual options vary but are generally over four years, with the exception of performance based stock options. Pursuant to the 2014 Plan, the Company granted performance based stock options to the Company’s former CEO in March 2016. This performance based stock option award was subject to the CEO’s continued service to the Company through each applicable vesting date. Upon the former CEO’s resignation from the Company in March 2019, the unvested shares subject to this award as of the separation date have been cancelled. A summary of shares available for grant under the Stock Plans is as follows: Shares Available for Grant Balance at December 31, 2018 2,980,762 Additional shares reserved 1,210,541 Allowance for PSU for overperformance (277,778 ) Shares forfeited for tax 38,696 Options, RSUs and PSUs granted (1,077,178 ) Options, RSUs and PSUs cancelled 527,963 Balance at December 31, 2019 3,403,006 Additional shares reserved 1,261,774 Allowance for PSU for overperformance (43,966 ) Shares forfeited for tax 62,782 Options, RSUs and PSUs granted (341,901 ) Options, RSUs and PSUs cancelled 258,486 Balance at December 31, 2020 4,600,181 Additional shares reserved 1,383,322 Allowance for PSU for overperformance (24,830 ) Shares forfeited for tax 58,787 Options, RSUs and PSUs granted (425,266 ) Options, RSUs and PSUs cancelled 140,101 Balance at December 31, 2021 5,732,295 A summary of stock option activity under the Stock Plans is as follows: Options Outstanding Weighted Average Number of Weighted Average Remaining Aggregate Options Exercise Price Contractual Term Intrinsic Value (in years) (in thousands) Outstanding at December 31, 2018 2,529,740 $ 46.72 6.7 $ 21,866 Options granted 244,075 $ 56.71 Options exercised (828,722 ) $ 34.52 $ 42,695 Options cancelled (298,908 ) $ 66.22 Outstanding at December 31, 2019 1,646,185 $ 50.80 6.3 $ 109,870 Options exercised (756,797 ) $ 45.75 $ 62,367 Options cancelled (76,238 ) $ 59.38 Outstanding at December 31, 2020 813,150 $ 54.69 5.9 $ 96,286 Options exercised (90,582 ) $ 47.82 $ 6,948 Options cancelled (21,914 ) $ 43.52 Outstanding at December 31, 2021 700,654 $ 55.93 4.8 $ 18,287 Options exercisable as of December 31, 2021 599,295 $ 56.06 4.4 $ 15,656 Options vested, exercisable or expected to vest as of December 31, 2021 696,003 $ 55.92 4.8 $ 18,173 The aggregate intrinsic value of options exercised is the difference between the estimated fair market value of the Company’s common stock at the date of exercise and the exercise price for in-the-money options. The aggregate intrinsic value of outstanding options is the difference between the closing price as of the date outstanding and the exercise price of the underlying stock options. The weighted-average grant-date fair value of options granted during the year ended December 31, 2019 was $27.91 per share. No options were granted during the years ended December 31, 2021 and 2020. The total fair value of options vested during the years ended December 31, 2021, 2020 and 2019 was approximately $3.1 million, $6.6 million and $8.3 million, respectively, based on the grant date fair value. The options outstanding and vested under the Stock Plans by exercise price, at December 31, 2021, were as follows: Options Outstanding Options Vested Weighted Average Remaining Number Contractual Term Weighted Average Number Weighted Average Exercise Price Outstanding (in years) Exercise Price Exercisable Exercise Price $3.60 — $36.55 116,179 3.15 $ 19.18 111,929 $ 18.52 $38.79 — $45.04 114,032 5.52 $ 47.12 94,094 $ 42.08 $45.07 — $63.23 156,883 4.48 $ 57.56 129,344 $ 59.12 $63.39 — $64.95 141,004 6.94 $ 64.28 91,835 $ 64.21 $65.51 — $87.62 152,556 3.95 $ 79.37 152,093 $ 79.36 $97.52 20,000 4.62 $ 97.52 20,000 $ 97.52 $3.60 — $97.52 700,654 4.81 $ 55.93 599,295 $ 56.06 Restricted Stock Units In 2015, the Company began granting restricted stock units (RSUs) under the 2014 Plan. Holders of RSUs do not have stockholder rights. Upon the release of RSUs, the Company issues new common stock from its authorized shares. RSUs generally vest four years from the date of grant. A summary of RSU activity under the Stock Plans was as follows: Number of Weighted Average Aggregate Restricted Grant Date Intrinsic Value Stock Units Fair Value (in thousands) Outstanding at December 31, 2018 1,002,161 $ 72.55 $ 38,974 Restricted stock granted 721,992 $ 58.37 Restricted stock released (321,858 ) $ 70.89 $ 4,064 Restricted stock cancelled (225,074 ) $ 70.51 Outstanding at December 31, 2019 1,177,221 $ 64.70 $ 138,371 Restricted stock granted 252,703 $ 123.31 Restricted stock released (395,971 ) $ 66.42 $ 23,789 Restricted stock cancelled (180,976 ) $ 71.26 Outstanding at December 31, 2020 852,977 $ 79.87 $ 147,650 Restricted stock granted 368,230 $ 146.64 Restricted stock released (346,602 ) $ 76.26 $ 22,902 Restricted stock cancelled (110,799 ) $ 98.76 Outstanding at December 31, 2021 763,806 $ 110.96 $ 61,922 Restricted stock expected to vest as of December 31, 2021 696,348 $ 109.78 $ 56,453 The aggregate intrinsic value of RSUs released is calculated using the fair market value of the Company’s common stock at the date of release. The aggregate intrinsic value of outstanding RSUs is calculated based on the closing price of the Company’s common stock as of the date outstanding. Performance Stock Units Pursuant to the 2014 Plan, the Company granted performance based RSUs to the former CEO in March 2016. The performance based RSUs are subject to the former CEO’s continued service to the Company through each applicable vesting date. If a performance metric is not met within the time limits specified in the RSU agreement, the shares subject to vesting under the vesting tranche for that performance metric will be cancelled. Upon the former CEO’s resignation from the Company in March 2019, the unvested shares subject to this award as of the separation date have been cancelled. In March 2019, the Company granted performance stock units (PSUs) to the current CEO, subject to his continued service to the Company and based on the total shareholder return (the TSR) of the Company’s common stock price compared to the S&P Healthcare Equipment Select Industry Index (the Index) over a three-year 0 to 3.5 times In March 2020, the Company granted PSUs to certain members of the management team. The number of shares to be issued upon vesting was based on the total shareholder return of the Company’s common stock compared to the Index, as well as certain performance criteria related to a specific financial target over a two-year performance period. For the three months ended March 31, 2020, the Company determined that the achievement status for these PSUs was not possible, and therefore did not record stock-based compensation expenses related to these grants. During the three months ended June 30, 2020, the Company modified the performance criteria for these PSUs to reflect the changed market conditions as a result of the COVID-19 pandemic, such that the remaining performance criteria is based on total shareholder return compared to the Index. The Company also granted PSUs that incorporated the same modified performance criteria to the Company’s Chief Executive Officer PSUs. Additional similar PSUs were issued to new members of management in the year ended December 31, 2020. In 2021, the Company granted PSUs to certain member of the management team, subject to continued service to the Company and based on the TSR of the Company’s common stock price compared to the Index over a three-year A summary of PSU activity under the Stock Plans was as follows: Number of Weighted Average Aggregate Restricted Grant Date Intrinsic Value Stock Units Fair Value (in thousands) Outstanding at December 31, 2018 7,962 $ 54.50 $ 310 PSU granted 111,111 $ 67.29 PSU released (3,981 ) $ 54.50 $ — PSU cancelled (3,981 ) $ 54.50 Outstanding at December 31, 2019 111,111 $ 67.29 $ 13,060 PSU granted 89,198 $ 128.71 PSU cancelled (1,272 ) $ 125.27 Outstanding at December 31, 2020 199,037 $ 94.20 $ 34,453 PSU granted 57,036 $ 183.20 PSU cancelled (7,388 ) $ 136.77 Outstanding at December 31, 2021 248,685 $ 113.35 $ 20,161 PSU expected to vest as of December 31, 2021 247,815 $ 113.22 $ 20,090 The aggregate intrinsic value of outstanding PSUs is calculated based on the closing price of the Company’s common stock as of the date outstanding. 2014 Employee Stock Purchase Plan In October 2014, the Board adopted the 2014 Employee Stock Purchase Plan (the ESPP). A total of 196,666 shares of common stock were initially available for future issuance under the 2014 Employee Stock Purchase Plan, subject to an annual increase on January 1 of each year. The ESPP provides eligible employees with an opportunity to purchase shares of the Company’s common stock through payroll deductions of up to 15% of their eligible compensation, subject to plan limitations. Under the ESPP, the purchase price of the Company stock is equal to 85% of the lower of its fair market value at the start and end of a six-month A summary of ESPP activity was as follows: December 31, 2021 2020 2019 Additional shares reserved 235,590 315,443 302,635 Shares issued 65,197 79,967 164,960 Shares available for future issuance 1,567,514 1,397,121 1,161,645 Employee contributions for shares issued (in thousands) $ 6,849 $ 7,513 $ 6,544 Employee Stock-Based Compensation The Company estimated the fair value of stock options granted to employees and shares purchased by employees under the ESPP using the Black-Scholes option valuation model. The fair value is amortized on a straight-line basis over the requisite service period of the awards, with the exception of performance based stock options whose fair value is recorded as expenses based on the probability that the performance metrics will be achieved. The following assumptions were used in estimating the fair value: Years Ended December 31, 2021 2020 2019 Stock Options: Expected term (in years) N/A N/A 5.7 Expected volatility N/A N/A 51% — 52% Risk-free interest rate N/A N/A 1.4% — 2.6% Dividend Yield N/A N/A 0% ESPP: Expected term (in years) 0.5 0.5 0.5 Expected volatility 36% — 49% 39% — 68% 48% — 61% Risk-free interest rate 0.1% 0.1% — 0.2% 1.6% — 2.4% Dividend Yield 0% 0% 0% The Company accounts for RSUs at their fair value, based on the closing market price of the Company’s common stock on the grant date. The fair value is amortized on a straight-line basis over the requisite service period of the awards, which is generally the vesting term of four years. In 2016, the Company granted performance based RSUs to its former CEO that only vest upon the achievement of specific operational performance criteria. The stock-based compensation for these performance based RSUs are recognized as expenses when it is determined that achieving the performance metrics are probable. Upon the former CEO’s resignation from the Company in March 2019, the unvested shares subject to this award as of the separation date have been cancelled. In connection with the former CEO’s resignation in March 2019, the Company amended the terms of his then vested nonqualified stock options such that they remain exercisable through the second anniversary of his separation date. This modification resulted in a charge of $1.6 million in stock-based compensation. In 2019, the Company granted PSUs to its current CEO that only vest based on the total shareholder return (TSR) of the Company common stock price relative to that of the Index. In 2020 and 2021, the Company granted PSUs to the CEO and other members of its management team that vest based on the total shareholder return of the Company common stock price relative to that of the Index. The company estimates the grant-date fair value of these PSUs based on the Monte Carlo simulation model and records the related stock-based compensation over the period for which the TSR is measured against the Index, which is generally two to three years. The use of the Monte Carlo simulation model requires the input the following assumptions: Years Ended December 31, 2021 2020 2019 Index volatility 51% — 53% 44% — 51% 36% Company volatility 49% — 54% 57% — 59% 45% Risk-free interest rate 0.1% — 0.3% 0.1% — 0.2% 2.4% Correlation with index 0.32 — 0.35 0.38 — 0.41 0.28 Dividend Yield 0% 0% 0% A summary of stock-based compensation expense by line items in the consolidated statements of operations is as follows (in thousands): Years Ended December 31, 2021 2020 2019 Cost of revenue $ 1,637 $ 2,433 $ 3,061 Research and development 6,455 6,141 6,323 Sales, general and administrative 36,273 34,081 32,313 Total stock-based compensation expense $ 44,365 $ 42,655 $ 41,697 A summary of pre-tax stock-based compensation expense by category was as follows (in thousands): Years Ended December 31, 2021 2020 2019 Stock options $ 2,997 $ 6,289 $ 10,312 Restricted stock units 29,234 27,977 26,854 Performance stock units 10,017 5,694 1,991 Employee stock purchase plan 2,117 2,695 2,540 Total stock-based compensation expense $ 44,365 $ 42,655 $ 41,697 As of December 31, 2021, total stock-based compensation expense not yet recognized, net of estimated forfeitures, are as follows: Unrecognized Weighted-Average Compensation Amortization Period (in thousands) (in years) Stock options $ 2,597 1.2 Restricted stock units 61,107 2.1 Performance stock units 10,389 0.7 Employee stock purchase plan 1,219 0.4

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The components of the Company’s income / (loss) before income taxes were as follows: Years Ended December 31, 2021 2020 2019 (in thousands) Domestic $ (129,135 ) $ (83,893 ) $ (106,010 ) Foreign (1,691 ) 1,696 3,923 Total loss before income taxes $ (130,826 ) $ (82,197 ) $ (102,087 ) The components of the expense / (benefit) for income taxes are as follows (in thousands): Years Ended December 31, 2021 2020 2019 Current: Federal $ — $ — $ (103 ) State 244 188 187 Foreign 585 656 1,644 Total current income tax expense / (benefit) 829 844 1,728 Deferred: Federal — — — State — — — Foreign (295 ) 24 (129 ) Total deferred income tax expense / (benefit) (295 ) 24 (129 ) Total income tax expense / (benefit) $ 534 $ 868 $ 1,599 Income tax expense differs from the amount computed by applying the statutory federal income tax rate as follows: Years Ended December 31, 2021 2020 2019 Tax at statutory federal rate 21.0 % 21.0 % 21.0 % State tax, net of federal benefit (0.2 )% (0.2 )% (0.1 )% Foreign rate differential (0.5 )% (0.4 )% (0.7 )% Tax credits 3.0 % 1.4 % 3.0 % Stock-based compensation (0.2 )% 9.8 % 3.8 % Change in valuation allowance (23.3 )% (33.6 )% (26.4 )% Other (0.2 )% 0.9 % (2.2 )% Total (0.4 )% (1.1 )% (1.6 )% The tax effects of temporary differences and carryforwards that give rise to significant portions of deferred tax assets and liabilities are as follows: December 31, 2021 2020 (in thousands) Net operating loss carryforwards $ 154,614 $ 127,347 Tax credits 25,087 18,919 Depreciation 650 662 Stock-based compensation 6,969 7,390 Accruals and reserves 13,404 9,531 Right of use asset 4,225 5,055 Other 1,130 869 Gross deferred tax assets 206,079 169,773 Valuation allowance (201,088 ) (164,278 ) Deferred tax assets 4,991 5,495 Lease liabilities (3,660 ) (4,459 ) Deferred tax liabilities (3,660 ) (4,459 ) Net deferred tax assets $ 1,331 $ 1,036 Realization of deferred tax assets is dependent upon future earnings, if any, the timing and amount of which are uncertain. Accordingly, substantially all of the net deferred tax assets have been offset by a valuation allowance. The valuation allowance increased by $36.8 million and $32.5 million for the years ended December 31, 2021 and 2020, respectively. As of December 31, 2021, the Company had federal net operating loss carryforwards (NOLs) of approximately $588.4 million, of which $329.4 million was generated in fiscal year 2018 and thereafter, which can be carried forward indefinitely under the 2017 Tax Act, as well as state NOLs of approximately $336.5 million, of which $54.3 million may be carried forward indefinitely. If not utilized, the remaining federal NOLs will begin to expire in 2026, and the remaining state NOLs will begin to expire in 2022. As of December 31, 2021, the Company had research and development credit carryforwards of approximately $20.5 million and $13.9 million for federal and California state income tax purposes, respectively. The federal credit carryforward begins expiring in 2026, and the state credits carry forward indefinitely. Under Section 382 of the Internal Revenue Code of 1986, as amended, the Company’s ability to utilize NOLs or other tax attributes such as research tax credits, in any taxable year may be limited if the Company experiences, or has experienced, a Section 382 “ownership change.” A Section 382 “ownership change” generally occurs if one or more stockholders or groups of stockholders, who own at least 5% of the Company’s stock, increase their ownership by a greater than 50 percentage point change (by value) over a rolling three-year period. Similar rules may apply under state tax laws. As a result of the Company’s June 2015 underwritten public offering, the Company experienced a Section 382 “ownership change.” The Company currently estimates that this “ownership change” will not inhibit its ability to utilize its NOLs. However, the Company may, in the future, experience one or more additional Section 382 “ownership changes” as a result of subsequent changes in its stock ownership, some of which changes are outside the Company’s control. If so, the Company may not be able to utilize a material portion of its NOLs and tax credits, even if the Company achieves profitability. The Company had unrecognized tax benefits (UTBs) of approximately $10.4 million as of December 31, 2021. The following table summarizes the activity related to UTBs (in thousands): Balance at December 31, 2018 $ 5,200 Increases related to current year tax provisions 1,611 Increases related to prior year tax provisions 572 Decreases related to prior year tax provisions — Balance at December 31, 2019 7,383 Increases related to current year tax provisions 891 Increases related to prior year tax provisions — Decreases related to prior year tax provisions (54 ) Balance at December 31, 2020 8,220 Increases related to current year tax provisions 1,412 Increases related to prior year tax provisions 860 Decreases related to prior year tax provisions (62 ) Balance at December 31, 2021 $ 10,430 If these UTBs were recognized, approximately $10.4 million would affect the effective tax rate before consideration of the valuation allowance. The Company files U.S. federal and state income tax and foreign income tax returns with varying statutes of limitations. The Company’s U.S. federal and the majority of state tax years from inception in 2006 onward will remain open to examination due to the carryover of the unused NOLs and tax credits. The Company does not have any material active tax audits or other proceedings pending, and believes it has provided adequate reserves for all tax deficiencies or reductions in tax benefits that could result from federal, state and foreign tax audits. The Company does not expect any material changes to the estimated amount of liability associated with its uncertain tax positions within the next twelve months. In accordance with ASC 740, Income Taxes

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Loss Per Share	12. Net Loss Per Share The following table summarizes the computation of basic and diluted net loss per share (in thousands, except share and per share data): Years Ended December 31, 2021 2020 2019 Net loss $ (131,360 ) $ (83,065 ) $ (103,686 ) Weighted average shares used to compute basic and diluted net loss per share 34,823,258 33,677,641 30,803,872 Net loss per share, basic and diluted $ (3.77 ) $ (2.47 ) $ (3.37 ) Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period, determined using the treasury-stock method, if inclusion of these is dilutive. The conversion spread for the Company’s outstanding convertible senior notes will have a dilutive impact on diluted net income per share of common stock when the average market price of the Company’s common stock for a given period exceeds the conversion price of $105.00 for the 2025 Notes. In connection with the issuance of the 2021 Notes and 2025 Notes, the Company entered into convertible bond hedges. The convertible bond hedges are not included for purposes of calculating the number of diluted shares outstanding for the periods presented, as their effect would be anti-dilutive. The convertible bond hedges are generally expected, but not guaranteed, to reduce the potential dilution and/or offset the cash payments the Company is required to make upon conversion of the 2021 Notes and 2025 Notes. When the 2021 Notes matured on June 1, 2021, the Company exercised its option under the bond hedge. As of December 31, 2021, the bond hedges related to the 2021 Notes are no longer outstanding. Because the Company has reported a net loss for all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods. The following potentially dilutive securities outstanding at the end of the periods presented have been excluded from the computation of diluted shares outstanding: December 31, 2021 2020 2019 Unreleased restricted and performance stock units 1,012,491 1,052,014 1,288,332 Options to purchase common stock 700,654 813,150 1,646,185 Convertible senior notes 1,807,141 3,597,174 1,790,033 Warrants related to the issuance of convertible senior notes 1,807,141 3,597,174 1,790,033 Total 5,327,427 9,059,512 6,514,583 .

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2021
Postemployment Benefits [Abstract]
Employee Benefit Plan	13. Employee Benefit Plan. In 2007, the Company adopted a 401(K) plan for its employees whereby eligible employees may contribute up to the maximum amount permitted by the Internal Revenue Code of 1986, as amended. In June 2016, the Company adopted a policy to match a portion of employee contributions for all qualified employees participating in the 401(k) plan. For the years ended December 31, 2021, 2020 and 2019, the Company recorded expenses of $2.9 million, $2.6 million and $3.1 million for matching contributions, respectively.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation These consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (U.S. GAAP). The consolidated financial statements include the Company’s accounts and those of its five operational wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated.
Other Risks And Uncertainties	Other Risks and Uncertainties The Company is subject to risks related to the public health crises such as the global pandemic associated with COVID-19, which has spread to most countries and all 50 states within the United States. The COVID-19 outbreak has negatively impacted, and continues to negatively impact, our operations, revenues and overall financial condition and demand for elective procedures remains unpredictable. Additionally, overall patient willingness to pursue elective procedures has decreased due to the pandemic. Although some restrictions on elective procedures have eased, the effect of the pandemic and recent surges in cases continue to affect patient willingness for interventional therapy for chronic pain and the number of elective procedures being performed. These challenges will likely continue for the duration of the pandemic, which is uncertain, and will affect our revenue while the pandemic continues. In addition, the Company is also subject to risks common to medical device companies, including, but not limited to, new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, product liability, manufacturing quality and scaling, continued reimbursement from third-party payors, There can be no assurance that the Company’s products or services will continue to be accepted in its existing marketplaces, nor can there be any assurance that any future products or services can be developed or manufactured at an acceptable cost and with appropriate performance characteristics, or that such products or services will be successfully marketed, if at all. The Company may choose to raise additional funds to further enhance its research and development efforts, for product expansion opportunities or to acquire a new business or products that are complementary to its business. There can be no assurance that such financing will be available or will be at terms acceptable by the Company.
Segments	Segments The chief operating decision maker for the Company is the Chief Executive Officer. The Chief Executive Officer reviews financial information presented on a consolidated basis, accompanied only by information about revenue by geographic region, for purposes of allocating resources and evaluating financial performance. The Company has one business activity and there are no segment managers who are held accountable for operations, operating results or plans for levels or components below the consolidated unit level, other than revenue. Accordingly, the Company has determined that it has a single reportable and operating segment structure. The Company and its Chief Executive Officer evaluate performance based primarily on revenue in the geographic locations in which the Company operates. Until 2015, the Company had derived most of its revenue from sales to customers in Australia and Europe. In May 2015, the U.S. Food and Drug Administration (FDA) approved the Company’s premarket approval (PMA) application to market Senza in the United States and the Company launched sales in the United States in 2015. Revenue by geography is based on the billing address of the customer. Long-lived assets and operating income outside the United States are not material; therefore, disclosures have been limited to revenue.
Foreign Currency Translation	Foreign Currency Translation The Company’s consolidated financial statements are prepared in U.S. dollars (USD). Its foreign subsidiaries in Europe and Australia use their local currency as their functional currency and maintain their records in the local currency. Accordingly, the assets and liabilities of these subsidiaries are translated into USD using the current exchange rates in effect at the balance sheet date and equity accounts are translated into USD using historical rates. Revenues and expenses are translated using the monthly average exchange rates during the period when the transaction occurs. The resulting foreign currency translation adjustments from this process are recorded in accumulated other comprehensive income (loss) in the consolidated balance sheets. Unrealized foreign exchange gains and losses from the remeasurement of assets and liabilities denominated in currencies other than the functional currency of the reporting entity are recorded in other income (expense), net. The Company recorded net unrealized foreign currency transaction losses of $ 3.3 million during the yea r ended December 31, 20 2 1 , gains of $ million during the year en ded December 31, 20 20 and gains of $ million during the year ended December 31, 201 9 . Additionally, realized gains and losses resulting from transactions denominated in currencies other than the local currency are recorded in other in come (expense), net . The Company recorded realized foreign currency transaction gains of $ 2.6 million during the year ended December 31, 20 2 1 , losses of $ million during the year ended December 31, 20 20 and losses of $ million during the year ended December 31, 201 9 . To the extent that the Company’s international operations grow, the effect of fluctuations in currency rates will become greater, and the Company will continue to reassess its approach to managing this risk. In addition, currency fluctuations or a weakening U.S. dollar can increase the costs of the Company’s international expansion. To date, the Company has not entered into any foreign currency hedging contracts. Based on its current international structure, the Company does not plan on engaging in hedging activities in the near future.
Use of Estimates	Use of Estimates The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Significant accounting estimates and management judgments reflected in the consolidated financial statements include items such as allowances for doubtful accounts; warranty obligations; stock-based compensation; depreciation and amortization lives; inventory valuation; valuation of investments; loss contingencies; and accounting for income taxes. Estimates are based on historical experience, where applicable, and other assumptions believed to be reasonable by management. Actual results may differ from those estimates under different assumptions or conditions.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash, cash equivalents and investments. The majority of the Company’s cash is held by one financial institution in the United States in excess of federally insured limits. The Company maintained investments in money market funds that were not federally insured during the years ended December 31, 2021 and 2020, and held cash in foreign banks of approximately $8.6 million and $17.6 million at December 31, 2021 and 2020, respectively, that was not federally insured. The Company has not experienced any losses on its deposits of cash and cash equivalents. The Company’s convertible note hedge transactions, entered into in connection with the 2025 Notes, subject the Company to credit risk such that the counterparties may be unable to fulfill the terms of the transactions. The associated risk is mitigated by limiting the counterparties to major financial institutions. In the international markets in which the Company participates, the Company uses both a direct sales force and distributors to sell its products, while in the United States the Company generally utilizes a direct sales force. The Company performs ongoing credit evaluations of some of its direct customers and distributors, does not require collateral, and maintains allowances for potential credit losses on customer accounts when deemed necessary.
Credit Losses	Credit Losses In June 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments
Fair Value of Financial Instruments	Fair Value of Financial Instruments Carrying amounts of certain of the Company’s financial instruments, including cash equivalents, short term investments, accounts receivable, accounts payable and accrued liabilities approximate fair value due to their relatively short maturities.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less at the date of purchase to be cash equivalents.
Investment Securities	Investment Securities The Company classifies its investment securities as available-for-sale. The Company classifies these investment securities as short-term or long-term based on the nature of the investment, its maturity date and its availability for use in current operations. Those investments with original maturities greater than three months at the date of purchase and remaining maturities of less than 12 months are considered short-term investments. Those investments with remaining maturities greater than 12 months are also classified as short-term investments as management considers them to be available for current operations if needed. The Company’s investment securities are recorded at fair value based on the fair value hierarchy. Money market funds and treasury bonds are classified within Level 1 of the fair value hierarchy, and agency bonds, commercial paper and corporate notes are classified within Level 2 of the fair value hierarchy. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security as an adjustment to yield using the straight-line interest method. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold.
Inventories	Inventories Inventories are stated at the lower of cost or net realizable value. Cost is determined using the standard cost method which approximates the first-in, first-out basis. Net realizable value is determined as the prices in the ordinary course of business, less reasonably predictable costs of completion, disposal and transportation. The Company regularly reviews inventory quantities compared to forecasted sales to record a provision for excess and obsolete inventory when appropriate. The Company estimates forecasted sales by considering product acceptance in the marketplace, customer demand, historical sales, product obsolescence and technological innovations. The Company’s policy is to write down inventory that has become obsolete, inventory that has a cost basis in excess of its expected lower of cost or net realizable value, and inventory in excess of expected requirements. The estimate of excess quantities is judgmental and primarily dependent on the Company’s estimates of future demand for a particular product. If the estimate of future demand is inaccurate based on actual sales, the Company may increase the write-down for excess inventory for that component and record a charge to inventory impairment in the accompanying consolidated statements of operations and comprehensive loss. The Company’s estimation of the future demand for a particular component of the Company’s products may vary and may result in changes in estimates in any particular period.
Shipping and Handling Costs	Shipping and Handling Costs Shipping and handling costs are expensed as incurred and are included in cost of revenue.
Revenue Recognition	Revenue Recognition The Company has revenue arrangements that generally consist of a single performance obligation, although, in some instances, revenue arrangements may consist of two performance obligations. The Company recognizes revenue at the point in time when it transfers control of promised goods to its customers. Revenue is measured as the amount of consideration it expects to receive in exchange for transferring goods. Revenue is recognized when obligations under the terms of a contract with customers are satisfied, which occurs with the transfer of control of the Company’s goods to its customers. Revenue is measured as the amount of consideration the Company expects to receive in exchange for transferring the goods. For a majority of sales, where the Company’s sales representative delivers its product at the point of implantation at hospitals or medical facilities, the Company recognizes revenue upon completion of the procedure and authorization, which represents the point in time when control transfers to the customers. For the remaining sales, which are sent from the Company’s distribution centers directly to hospitals and medical facilities, as well as distributor sales, where product is ordered in advance of an implantation, the transfer of control occurs at the time of shipment of the product. These customers are obligated to pay within specified terms regardless of when or if they ever sell or use the products. The Company does not offer rights of return or price protection. Sales, value add, and other taxes the Company collects concurrent with revenue-producing activities are excluded from revenue. The expected costs associated with warranty obligations continue to be recognized as expense when the products are sold (see Note 7). The Company periodically provides incentive offers, in the form of rebates, to customers based on their aggregate levels of purchases. Product revenue is recorded net of such incentive offers. Practical Expedients and Exemptions - The Company recognizes revenue upon the transfer of control of the product and there are no material future performance obligations beyond such transfer. As a result, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. The Company does not capitalize incremental costs when the amortization period of the asset is less than a year
Allowance for Doubtful Accounts	Allowance for Doubtful Accounts The Company makes estimates of the collectability of accounts receivable and provide an allowance for accounts receivable considered uncollectible based on current expected credit losses. In doing so, the Company analyzes historical bad debt trends, customer concentrations, customer credit worthiness, the age of the receivable, current economic trends and changes in customer payment patterns when evaluating the adequacy of the allowance for doubtful accounts. For the years ended December 31, 2021, 2020 and 2019, the Company recognized bad debt expenses of $0.1 million, $2.8 million and $1.3 million, respectively.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation of property and equipment, other than leasehold improvements, is computed using the straight-line method over the assets’ estimated useful lives of three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful life of the asset or the life of the lease. Upon retirement or sale, the cost and related accumulated depreciation are removed from the consolidated balance sheet and the resulting gain or loss is reflected in operations. Maintenance and repairs are charged to operations as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group might not be recoverable. When such an event occurs, management determines whether there has been impairment by comparing the anticipated undiscounted future net cash flows to the related asset group’s carrying value. If an asset is considered impaired, the asset is written down to fair value, which is determined based either on discounted cash flows or appraised value, depending on the nature of the asset. There were no impairment charges, or changes in estimated useful lives , recorded through December 31, 20 2 1 .
Lease Accounting	Lease Accounting The Company has operating leases for office space, warehouse, research and development facilities, manufacturing facilities and equipment. Leases with terms of 12 months or less are not recorded on the balance sheet, as the related lease expenses are recognized on a straight-line basis over the lease term. The Company accounts for lease components (such as fixed payments) separately from nonlease components (such as common area expenses). Operating lease assets and operating lease liabilities are recognized based on the present value of minimum lease payments over the remaining lease term. The Company uses its incremental borrowing rate based on information available when determining the lease liabilities. Lease cost is recognized on a straight-line basis over the expected lease term.
Income Taxes	Income Taxes The Company records income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the Company’s consolidated financial statements or income tax returns. In estimating future tax consequences, expected future events other than enactments or changes in the tax law or rates are considered. Valuation allowances are provided when necessary to reduce deferred tax assets to the amount expected to be realized. The Company operates in various tax jurisdictions and is subject to audit by various tax authorities. To date, taxes paid have been predominantly due to income taxes in foreign and state jurisdictions in which we conduct business. The Company provides for tax contingencies whenever it is deemed probable that a tax asset has been impaired or a tax liability has been incurred for events such as tax claims or changes in tax laws. Tax contingencies are based upon their technical merits, relative tax law, and the specific facts and circumstances as of each reporting period. Changes in facts and circumstances could result in material changes to the amounts recorded for such tax contingencies. The Company records uncertain tax positions on the basis of a two-step process whereby (1) a determination is made as to whether it is more likely than not that the tax positions will be sustained based on the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold the Company recognizes the largest amount of tax benefit that is greater than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company’s policy is to recognize interest and penalties related to income taxes as a component of income tax expense.
Other Comprehensive Income (Loss)	Other Comprehensive Income (Loss) Other comprehensive income (loss) represents all changes in stockholders’ equity except those resulting from distributions to stockholders. The Company’s unrealized gains on short-term available-for-sale investment securities and foreign currency translation adjustments represent the components of other comprehensive income (loss) that are excluded from the reported net loss and are presented in the consolidated statements of operations and comprehensive loss.
Research and Development	Research and Development Research and development expenses, including new product development, regulatory compliance, and clinical research, are charged to operations as incurred in the consolidated statements of operations and comprehensive loss. Such costs include personnel-related costs, including stock-based compensation, supplies, services, depreciation, allocated facilities and information services, clinical trial and related clinical manufacturing expenses, fees paid to investigative sites, and other indirect costs.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation arrangements with employees in accordance with Accounting Standards Codification (ASC) 718, Compensation—Stock Compensation. In March 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-09, Stock Compensation (Topic 718): Improvements to Employee Shared-Based Payment Accounting The Company’s determination of the fair value of stock options, other than performance-based awards, on the date of grant utilizes the Black-Scholes option-pricing model, and is impacted by its common stock price as well as changes in assumptions regarding a number of subjective variables. The expected term that the award will remain outstanding is based on the Company’s own historical data. The expected volatility over the term of the awards is based on the Company’s own common stock volatility and those of its peer group. The risk-free interest rate is based on the U.S. Treasury yield for zero-coupon U.S. Treasury notes with maturities. The expected dividend is zero, as the Company has never paid dividends and has no current plans to do so. The fair value of stock options is recognized over the period during which an optionee is required to provide services in exchange for the option award, known as the requisite service period (usually the vesting period), on a straight-line basis. Stock-based compensation expense recognized at fair value includes the impact of estimated forfeitures. The Company estimates future forfeitures at the date of grant and revises the estimates, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The Company estimates the fair value of the rights to purchase shares by employees under the Employee Stock Purchase Plan using the Black-Scholes option pricing formula. The Employee Stock Purchase Plan provides for consecutive six-month Equity instruments issued to non-employees are recorded at their fair value on the measurement date and are subject to periodic adjustments as the underlying equity instruments vest. The fair value of options granted to consultants is expensed when vested. The non-employee stock-based compensation expense was not material for all periods presented. The Company accounts for stock-based compensation for the restricted stock units at their fair value, based on the closing market price of the Company’s common stock on the grant date. These costs are recognized on a straight-line basis over the requisite service period, which is generally the vesting term of four years. The Company also issues stock options and restricted stock units with vesting based upon achievement of specific operational performance criteria. The fair value for these performance-based awards is recognized over the period during which the goals are to be achieved. Stock-based compensation expense recognized at fair value includes the impact of estimated probability that the goals would be achieved, which is assessed prior to the requisite service period for the specific goals. The Company additionally grants performance stock units with vesting based on its stock price performance compared to a specified target composite index over a certain period. The fair value of these grants is determined by using the Monte Carlo simulation model, which is based on a discounted cash flow approach, and requires inputs such as expected volatility of our stock price, expected volatility of the targeted composite index, correlation between the changes in our stock price and the target composite index, risk-free interest rate and expected dividends. The e xpected volatility of our stock and the target composite index is based on the historical data. Correlation is based on the historical relationship between our stock price and the target composite index . The risk-free interest rate is based upon the treasury yield consistent with the vesting term of the grant. The expected dividend yield is zero . Stock-based compensation for these performance stock units is recognized over the specified performance measurement period . Upon adoption of ASU 2016-09 as described above, excess tax benefits or deficiencies from share-based award activity are reflected in the consolidated statements of operations as a component of the provision for income taxes, whereas they were previously recognized as additional paid-in capital.
Net Loss per Share of Common Stock	Net Loss per Share of Common Stock Basic net loss per common share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common shares and potentially dilutive securities outstanding for the period. For purposes of the diluted net loss per share calculation, restricted stock units, common stock options and the conversion spread for the Company’s outstanding convertible senior notes are considered to be potentially dilutive securities. Because the Company has reported a net loss in all periods presented, diluted net loss per common share is the same as basic net loss per common share for those periods.
Recent Accounting Pronouncements	Recent Accounting Pronouncements Accounting Pronouncements Recently Adopted In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. This ASU eliminates certain exceptions related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period and the recognition of deferred tax liabilities for outside basis differences related to changes in ownership of equity method investments and foreign subsidiaries. The Company adopted ASU 2019-12 on January 1, 2021. The adoption of ASU 2019-12 did not have a material effect on the consolidated financial statements. Accounting Pronouncements Not Yet Effective In August 2020, the FASB issued ASU No. 2020-06, Debt - Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging - Contracts in Entity’s Own Equity (Subtopic 815-40)

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2021
Revenue From Contract With Customer [Abstract]
Summary of Revenue by Geography on Billing Address of Customer	The following table presents revenue by geography, based on the billing address of the customer (in thousands): Years Ended December 31, 2021 2020 2019 United States $ 326,216 $ 311,873 $ 326,012 International 60,689 50,175 64,243 Total revenue $ 386,905 $ 362,048 $ 390,255
Schedule of Revenue by Major Customers by Geographic Area	The United States is the only country that accounts for 10% or more of the revenue during the periods presented: Years Ended December 31, 2021 2020 2019 United States 84 % 86 % 84 %

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2021
Leases [Abstract]
Schedule of Weighted Average Lease Terms and Discounts Rates	The weighted average lease terms and discounts rates are as follows: December 31, 2021 2020 Operating Lease Term and Discount Rate Weighted-average remaining lease term 4.20 years 4.32 years Weighted-average discount rate 7.0% 7.0%
Schedule of Maturity of Lease Liabilities	As of December 31, 2021, t he maturity of lease liabilities are as follows (in thousands): Operating Leases 2022 $ 5,720 2023 6,019 2024 6,201 2025 2,849 2026 405 Thereafter 1,979 Total lease payments 23,173 Less: Interest (3,183 ) Present value of lease liabilities $ 19,990
Supplemental Lease Cost Information	Supplemental lease cost information are as follows (in thousands): Years Ended December 31, 2021 2020 Operating lease cost $ 5,243 $ 4,936
Schedule Of Operating Lease Assets and Liabilities	Supplemental balance sheet information are as follows (in thousands): December 31, 2021 2020 Operating Leases: Operating lease assets $ 17,577 $ 18,142 Other current liabilities $ 4,588 $ 3,876 Long term operating lease liabilities 15,402 16,689 Total operating lease liabilities $ 19,990 $ 20,565
Schedule of Supplemental Cash Flow Information Related to Lease	Supplemental cash flow information are as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flow from operating leases $ 5,253 $ 4,923

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2021
Fair Value Disclosures [Abstract]
Financial Instruments Measured at Fair Value on Recurring Basis	The following table sets forth the Company’s financial instruments that were measured at fair value on a recurring basis, by level, within the fair value hierarchy (in thousands): Balance as of December 31, 2021 Level 1 Level 2 Level 3 Total Assets: Money market funds (i) $ 9,562 $ — $ — $ 9,562 Agency bonds (ii) — 42,538 — 42,538 Commercial paper (ii) — 61,884 — 61,884 Corporate notes (iii) — 30,351 — 30,351 Treasury bonds (ii) 197,552 — — 197,552 Total assets $ 207,114 $ 134,773 $ — $ 341,887 Balance as of December 31, 2020 Level 1 Level 2 Level 3 Total Assets: Money market funds (i) $ 16,273 $ — $ — $ 16,273 Agency bonds (ii) — 210,302 — 210,302 Commercial paper (ii) — 277,602 — 277,602 Corporate notes (ii) — 25,395 — 25,395 Treasury bonds (ii) 30,074 — — 30,074 Total assets $ 46,347 $ 513,299 $ — $ 559,646 (i) Included in cash and cash equivalents on the consolidated balance sheets. (ii) Included in short-term investments on the consolidated balance sheets. (iii) Included in either cash and cash equivalents or short-term investments on the consolidated balance sheets.

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Summary of Gross Unrealized Gains and Unrealized Losses of Investment Securities Excluding Investments in Money Market Funds	The following is a summary of the gross unrealized gains and unrealized losses on the Company’s investment securities (in thousands): December 31, 2021 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value Investment Securities Agency bonds $ 42,546 $ — $ (8 ) $ 42,538 Commercial paper 61,886 2 (4 ) 61,884 Corporate notes 30,371 — (20 ) 30,351 Treasury bonds 197,889 2 (339 ) 197,552 Total securities $ 332,692 $ 4 $ (371 ) $ 332,325 December 31, 2020 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Aggregate Fair Value Investment Securities Agency bonds $ 210,225 $ 79 $ (2 ) $ 210,302 Commercial paper 277,593 23 (14 ) 277,602 Corporate notes 25,364 40 (9 ) 25,395 Treasury bonds 30,064 10 — 30,074 Total securities $ 543,246 $ 152 $ (25 ) $ 543,373
Summary of Contractual Maturities of Investment Securities	The amortized costs and estimated fair values of the Company’s available-for-sale securities by contractual maturities as of December 31, 2021 were as follows (in thousands): Amortized Cost Fair Value Amounts maturing within one year $ 305,844 $ 305,535 Amounts after one year through five years 26,848 26,790 Total investment securities $ 332,692 $ 332,325
Components of Inventories	Inventories (in thousands) December 31, 2021 2020 Raw materials $ 50,160 $ 34,405 Finished goods 43,357 48,891 Total inventories $ 93,517 $ 83,296
Schedule of Property and Equipment, Net and Depreciation and Amortization Expense	Property and Equipment, Net (in thousands) December 31, 2021 2020 Laboratory equipment $ 8,722 $ 7,072 Computer equipment and software 16,349 12,671 Furniture and fixtures 4,215 3,918 Leasehold improvements 10,316 4,289 Construction in process 3,717 3,354 Total 43,319 31,304 Less: Accumulated depreciation and amortization (22,655 ) (17,773 ) Property and equipment, net $ 20,664 $ 13,531
Summary of Accrued Liabilities	Accrued Liabilities (in thousands) December 31, 2021 2020 Accrued payroll and related expenses $ 30,957 $ 30,971 Accrued professional fees 6,547 2,101 Accrued taxes 1,074 1,191 Accrued clinical and research expenses 305 668 Accrued interest 1,305 1,548 Accrued warranty 664 699 Accrued other 4,665 6,127 Total accrued liabilities $ 45,517 $ 43,305

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Schedule of Activities Related to Warranty Obligations	Activities related to warranty obligations were as follows (in thousands): December 31, 2021 2020 Beginning Balance $ 699 $ 1,178 Provision for warranty 2,846 2,150 Utilization (2,881 ) (2,629 ) Ending Balance $ 664 $ 699

Long-term Debt (Tables)

Long-term Debt (Tables)	12 Months Ended
	Dec. 31, 2021
Debt Instrument [Line Items]
Interest Expense Recognized Related to Convertible Notes	The following table sets forth the interest expense recognized related to the 2021 Notes and 2025 Notes (in thousands): Years Ended December 31, 2021 2020 2019 Contractual interest expense $ 6,484 $ 6,860 $ 3,019 Amortization of debt discount 12,023 13,308 6,843 Amortization of debt issuance costs 1,240 1,634 1,063 Total interest expense $ 19,747 $ 21,802 $ 10,925
2021 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Net Carrying Amount of Convertible Debt	The net carrying amount of the liability component of the 2021 Notes was as follows (in thousands): December 31, 2020 Principal $ 172,500 Unamortized discount (3,182 ) Unamortized issuance cost (542 ) Net carrying amount $ 168,776
2021 Notes and Convertible Notes [Member] | Debt, Equity Component [Member]
Debt Instrument [Line Items]
Net Carrying Amount of Convertible Debt	The net carrying amount of the equity component of the 2021 Notes was as follows (in thousands): December 31, 2020 Debt discount related to value of conversion option $ 32,945 Debt issuance cost (1,179 ) Net carrying amount $ 31,766
2025 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Net Carrying Amount of Convertible Debt	The net carrying amount of the liability component of the 2025 Notes was as follows (in thousands): December 31, 2021 2020 Principal $ 189,750 $ 189,750 Unamortized discount (35,079 ) (43,919 ) Unamortized issuance cost (3,361 ) (4,060 ) Net carrying amount $ 151,310 $ 141,771
2025 Notes and Convertible Notes [Member] | Debt, Equity Component [Member]
Debt Instrument [Line Items]
Net Carrying Amount of Convertible Debt	The net carrying amount of the equity component of the 2025 Notes was as follows (in thousands): December 31, 2021 2020 Debt discount related to value of conversion option $ 49,947 $ 49,947 Debt issuance cost (1,607 ) (1,607 ) Net carrying amount $ 48,340 $ 48,340

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2021
Summary of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance as of December 31, 2021 was as follows: Shares Outstanding stock options and awards 1,713,145 Reserved for grants of future stock options and awards 6,078,869 Reserved for employee stock purchase plan 1,567,514 Total common stock reserved for future issuance 9,359,528
Summary of Shares Available for Grant	A summary of shares available for grant under the Stock Plans is as follows: Shares Available for Grant Balance at December 31, 2018 2,980,762 Additional shares reserved 1,210,541 Allowance for PSU for overperformance (277,778 ) Shares forfeited for tax 38,696 Options, RSUs and PSUs granted (1,077,178 ) Options, RSUs and PSUs cancelled 527,963 Balance at December 31, 2019 3,403,006 Additional shares reserved 1,261,774 Allowance for PSU for overperformance (43,966 ) Shares forfeited for tax 62,782 Options, RSUs and PSUs granted (341,901 ) Options, RSUs and PSUs cancelled 258,486 Balance at December 31, 2020 4,600,181 Additional shares reserved 1,383,322 Allowance for PSU for overperformance (24,830 ) Shares forfeited for tax 58,787 Options, RSUs and PSUs granted (425,266 ) Options, RSUs and PSUs cancelled 140,101 Balance at December 31, 2021 5,732,295
Summary of Activity under Stock Plans	A summary of stock option activity under the Stock Plans is as follows: Options Outstanding Weighted Average Number of Weighted Average Remaining Aggregate Options Exercise Price Contractual Term Intrinsic Value (in years) (in thousands) Outstanding at December 31, 2018 2,529,740 $ 46.72 6.7 $ 21,866 Options granted 244,075 $ 56.71 Options exercised (828,722 ) $ 34.52 $ 42,695 Options cancelled (298,908 ) $ 66.22 Outstanding at December 31, 2019 1,646,185 $ 50.80 6.3 $ 109,870 Options exercised (756,797 ) $ 45.75 $ 62,367 Options cancelled (76,238 ) $ 59.38 Outstanding at December 31, 2020 813,150 $ 54.69 5.9 $ 96,286 Options exercised (90,582 ) $ 47.82 $ 6,948 Options cancelled (21,914 ) $ 43.52 Outstanding at December 31, 2021 700,654 $ 55.93 4.8 $ 18,287 Options exercisable as of December 31, 2021 599,295 $ 56.06 4.4 $ 15,656 Options vested, exercisable or expected to vest as of December 31, 2021 696,003 $ 55.92 4.8 $ 18,173
Summary of Options Outstanding and Vested under Stock Plans by Exercise Price	The options outstanding and vested under the Stock Plans by exercise price, at December 31, 2021, were as follows: Options Outstanding Options Vested Weighted Average Remaining Number Contractual Term Weighted Average Number Weighted Average Exercise Price Outstanding (in years) Exercise Price Exercisable Exercise Price $3.60 — $36.55 116,179 3.15 $ 19.18 111,929 $ 18.52 $38.79 — $45.04 114,032 5.52 $ 47.12 94,094 $ 42.08 $45.07 — $63.23 156,883 4.48 $ 57.56 129,344 $ 59.12 $63.39 — $64.95 141,004 6.94 $ 64.28 91,835 $ 64.21 $65.51 — $87.62 152,556 3.95 $ 79.37 152,093 $ 79.36 $97.52 20,000 4.62 $ 97.52 20,000 $ 97.52 $3.60 — $97.52 700,654 4.81 $ 55.93 599,295 $ 56.06
Summary of Restricted Stock Units under the Stock Plan	A summary of RSU activity under the Stock Plans was as follows: Number of Weighted Average Aggregate Restricted Grant Date Intrinsic Value Stock Units Fair Value (in thousands) Outstanding at December 31, 2018 1,002,161 $ 72.55 $ 38,974 Restricted stock granted 721,992 $ 58.37 Restricted stock released (321,858 ) $ 70.89 $ 4,064 Restricted stock cancelled (225,074 ) $ 70.51 Outstanding at December 31, 2019 1,177,221 $ 64.70 $ 138,371 Restricted stock granted 252,703 $ 123.31 Restricted stock released (395,971 ) $ 66.42 $ 23,789 Restricted stock cancelled (180,976 ) $ 71.26 Outstanding at December 31, 2020 852,977 $ 79.87 $ 147,650 Restricted stock granted 368,230 $ 146.64 Restricted stock released (346,602 ) $ 76.26 $ 22,902 Restricted stock cancelled (110,799 ) $ 98.76 Outstanding at December 31, 2021 763,806 $ 110.96 $ 61,922 Restricted stock expected to vest as of December 31, 2021 696,348 $ 109.78 $ 56,453
Schedule of Employee Stock Purchase Plan Activity	A summary of ESPP activity was as follows: December 31, 2021 2020 2019 Additional shares reserved 235,590 315,443 302,635 Shares issued 65,197 79,967 164,960 Shares available for future issuance 1,567,514 1,397,121 1,161,645 Employee contributions for shares issued (in thousands) $ 6,849 $ 7,513 $ 6,544
Schedule of Fair Value of Employee Stock Options Using Black-Scholes Option Valuation and Monte Carlo Simulation Model	The following assumptions were used in estimating the fair value: Years Ended December 31, 2021 2020 2019 Stock Options: Expected term (in years) N/A N/A 5.7 Expected volatility N/A N/A 51% — 52% Risk-free interest rate N/A N/A 1.4% — 2.6% Dividend Yield N/A N/A 0% ESPP: Expected term (in years) 0.5 0.5 0.5 Expected volatility 36% — 49% 39% — 68% 48% — 61% Risk-free interest rate 0.1% 0.1% — 0.2% 1.6% — 2.4% Dividend Yield 0% 0% 0%
Summary of Stock-Based Compensation Expense by Line Items in Consolidated Statements of Operations	A summary of stock-based compensation expense by line items in the consolidated statements of operations is as follows (in thousands): Years Ended December 31, 2021 2020 2019 Cost of revenue $ 1,637 $ 2,433 $ 3,061 Research and development 6,455 6,141 6,323 Sales, general and administrative 36,273 34,081 32,313 Total stock-based compensation expense $ 44,365 $ 42,655 $ 41,697
Summary of Stock-Based Compensation Expense	A summary of pre-tax stock-based compensation expense by category was as follows (in thousands): Years Ended December 31, 2021 2020 2019 Stock options $ 2,997 $ 6,289 $ 10,312 Restricted stock units 29,234 27,977 26,854 Performance stock units 10,017 5,694 1,991 Employee stock purchase plan 2,117 2,695 2,540 Total stock-based compensation expense $ 44,365 $ 42,655 $ 41,697
Summary of Stock-Based Compensation Expense Not Yet Recognized	As of December 31, 2021, total stock-based compensation expense not yet recognized, net of estimated forfeitures, are as follows: Unrecognized Weighted-Average Compensation Amortization Period (in thousands) (in years) Stock options $ 2,597 1.2 Restricted stock units 61,107 2.1 Performance stock units 10,389 0.7 Employee stock purchase plan 1,219 0.4
Performance Stock Units [Member]
Summary of Performance Stock Units under the Stock Plan	A summary of PSU activity under the Stock Plans was as follows: Number of Weighted Average Aggregate Restricted Grant Date Intrinsic Value Stock Units Fair Value (in thousands) Outstanding at December 31, 2018 7,962 $ 54.50 $ 310 PSU granted 111,111 $ 67.29 PSU released (3,981 ) $ 54.50 $ — PSU cancelled (3,981 ) $ 54.50 Outstanding at December 31, 2019 111,111 $ 67.29 $ 13,060 PSU granted 89,198 $ 128.71 PSU cancelled (1,272 ) $ 125.27 Outstanding at December 31, 2020 199,037 $ 94.20 $ 34,453 PSU granted 57,036 $ 183.20 PSU cancelled (7,388 ) $ 136.77 Outstanding at December 31, 2021 248,685 $ 113.35 $ 20,161 PSU expected to vest as of December 31, 2021 247,815 $ 113.22 $ 20,090
Schedule of Fair Value of Employee Stock Options Using Black-Scholes Option Valuation and Monte Carlo Simulation Model	The company estimates the grant-date fair value of these PSUs based on the Monte Carlo simulation model and records the related stock-based compensation over the period for which the TSR is measured against the Index, which is generally two to three years. The use of the Monte Carlo simulation model requires the input the following assumptions: Years Ended December 31, 2021 2020 2019 Index volatility 51% — 53% 44% — 51% 36% Company volatility 49% — 54% 57% — 59% 45% Risk-free interest rate 0.1% — 0.3% 0.1% — 0.2% 2.4% Correlation with index 0.32 — 0.35 0.38 — 0.41 0.28 Dividend Yield 0% 0% 0%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Components of Loss before Income Taxes	The components of the Company’s income / (loss) before income taxes were as follows: Years Ended December 31, 2021 2020 2019 (in thousands) Domestic $ (129,135 ) $ (83,893 ) $ (106,010 ) Foreign (1,691 ) 1,696 3,923 Total loss before income taxes $ (130,826 ) $ (82,197 ) $ (102,087 )
Components of Expense/(Benefit) for Income Taxes	The components of the expense / (benefit) for income taxes are as follows (in thousands): Years Ended December 31, 2021 2020 2019 Current: Federal $ — $ — $ (103 ) State 244 188 187 Foreign 585 656 1,644 Total current income tax expense / (benefit) 829 844 1,728 Deferred: Federal — — — State — — — Foreign (295 ) 24 (129 ) Total deferred income tax expense / (benefit) (295 ) 24 (129 ) Total income tax expense / (benefit) $ 534 $ 868 $ 1,599
Income Tax Expense by Applying Statutory Federal Income Tax Rate	Income tax expense differs from the amount computed by applying the statutory federal income tax rate as follows: Years Ended December 31, 2021 2020 2019 Tax at statutory federal rate 21.0 % 21.0 % 21.0 % State tax, net of federal benefit (0.2 )% (0.2 )% (0.1 )% Foreign rate differential (0.5 )% (0.4 )% (0.7 )% Tax credits 3.0 % 1.4 % 3.0 % Stock-based compensation (0.2 )% 9.8 % 3.8 % Change in valuation allowance (23.3 )% (33.6 )% (26.4 )% Other (0.2 )% 0.9 % (2.2 )% Total (0.4 )% (1.1 )% (1.6 )%
Tax Effects of Temporary Differences and Carryforwards that Give Rise to Significant Portions of Deferred Tax Assets and Liabilities	The tax effects of temporary differences and carryforwards that give rise to significant portions of deferred tax assets and liabilities are as follows: December 31, 2021 2020 (in thousands) Net operating loss carryforwards $ 154,614 $ 127,347 Tax credits 25,087 18,919 Depreciation 650 662 Stock-based compensation 6,969 7,390 Accruals and reserves 13,404 9,531 Right of use asset 4,225 5,055 Other 1,130 869 Gross deferred tax assets 206,079 169,773 Valuation allowance (201,088 ) (164,278 ) Deferred tax assets 4,991 5,495 Lease liabilities (3,660 ) (4,459 ) Deferred tax liabilities (3,660 ) (4,459 ) Net deferred tax assets $ 1,331 $ 1,036
Summary of Unrecognized Tax Benefits	The following table summarizes the activity related to UTBs (in thousands): Balance at December 31, 2018 $ 5,200 Increases related to current year tax provisions 1,611 Increases related to prior year tax provisions 572 Decreases related to prior year tax provisions — Balance at December 31, 2019 7,383 Increases related to current year tax provisions 891 Increases related to prior year tax provisions — Decreases related to prior year tax provisions (54 ) Balance at December 31, 2020 8,220 Increases related to current year tax provisions 1,412 Increases related to prior year tax provisions 860 Decreases related to prior year tax provisions (62 ) Balance at December 31, 2021 $ 10,430

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2021
Earnings Per Share [Abstract]
Computation of Basic and Diluted Net Loss per Share	The following table summarizes the computation of basic and diluted net loss per share (in thousands, except share and per share data): Years Ended December 31, 2021 2020 2019 Net loss $ (131,360 ) $ (83,065 ) $ (103,686 ) Weighted average shares used to compute basic and diluted net loss per share 34,823,258 33,677,641 30,803,872 Net loss per share, basic and diluted $ (3.77 ) $ (2.47 ) $ (3.37 )
Computation of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Shares	The following potentially dilutive securities outstanding at the end of the periods presented have been excluded from the computation of diluted shares outstanding: December 31, 2021 2020 2019 Unreleased restricted and performance stock units 1,012,491 1,052,014 1,288,332 Options to purchase common stock 700,654 813,150 1,646,185 Convertible senior notes 1,807,141 3,597,174 1,790,033 Warrants related to the issuance of convertible senior notes 1,807,141 3,597,174 1,790,033 Total 5,327,427 9,059,512 6,514,583

Formation and Business of the_2

Formation and Business of the Company - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Apr. 30, 2020	Jun. 30, 2016	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Formation and Business of the Company [Line Items]
Net loss			$ 131,360,000	$ 83,065,000	$ 103,686,000
Cash used in operations			(41,881,000)	1,191,000	$ (50,225,000)
Accumulated deficit			$ 624,193,000	492,833,000
Common stock in underwriting public offering	1,868,750
Net proceeds from common stock	$ 147,100,000			$ 147,144,000
1.75% Convertible Senior Notes due 2021 [Member]
Formation and Business of the Company [Line Items]
Debt instrument due year		2021	2021	2021
Aggregate principal amount of convertible senior notes		$ 150,000,000
Net proceeds from the debt offering after deducting transaction costs		$ 166,200,000
2.75% Convertible Senior Notes due 2025 [Member]
Formation and Business of the Company [Line Items]
Debt instrument due year			2025	2025
Aggregate principal amount of convertible senior notes	189,800,000
Net proceeds from the debt offering after deducting transaction costs	$ 183,600,000

Formation and Business of the_3

Formation and Business of the Company - Additional Information - Public Offering (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Apr. 30, 2020	Jun. 30, 2016	Dec. 31, 2021	Dec. 31, 2020
Subsidiary Sale Of Stock [Line Items]
Common stock in underwriting public offering	1,868,750
Proceeds from issuance of common stock in public offering, net	$ 147,100,000			$ 147,144,000
Common Stock [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock in underwriting public offering	1,868,750			1,868,750
Over Allotment Option [Member]
Subsidiary Sale Of Stock [Line Items]
Common stock in underwriting public offering	243,750
1.75% Convertible Senior Notes due 2021 [Member]
Subsidiary Sale Of Stock [Line Items]
Aggregate principal amount of convertible senior notes		$ 150,000,000
Debt instrument interest rate		1.75%		1.75%
Debt instrument due year		2021	2021	2021
Additional aggregate principal amount of convertible senior notes		$ 22,500,000
Debt instrument frequency of payment			semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2016
Net proceeds from the debt offering after deducting transaction costs		$ 166,200,000
2.75% Convertible senior notes due 2025 [Member]
Subsidiary Sale Of Stock [Line Items]
Aggregate principal amount of convertible senior notes	$ 165,000,000
Debt instrument interest rate	2.75%
Debt instrument due year	2025
Additional aggregate principal amount of convertible senior notes	$ 24,800,000
Debt instrument frequency of payment	semi-annually in arrears on April 1 and October 1 of each year, commencing on October 1, 2020
Net proceeds from the debt offering after deducting transaction costs	$ 183,600,000

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Oct. 31, 2014	Dec. 31, 2021USD ($)SubsidiaryBusiness	Dec. 31, 2020USD ($)	Dec. 31, 2019USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operational wholly owned subsidiaries | Subsidiary		5
Number of business activities | Business		1
Net unrealized foreign currency transaction gains (losses)		$ (3,300,000)	$ 300,000	$ 1,000,000
Realized foreign currency transaction gains (losses)		2,600,000	(200,000)	(1,600,000)
Cash held in foreign banks		$ 8,600,000	17,600,000
Unsatisfied performance obligations description		The Company recognizes revenue upon the transfer of control of the product and there are no material future performance obligations beyond such transfer.  As a result, the Company does not disclose the value of unsatisfied performance obligations for (i) contracts with an original expected length of one year or less and (ii) contracts for which it recognizes revenue at the amount to which it has the right to invoice for services performed. The Company does not capitalize incremental costs when the amortization period of the asset is less than a year.
Bad debt expense		$ 100,000	$ 2,800,000	$ 1,300,000
Impairment charges		$ 0
Employee stock purchase plan offering period	6 months	6 months
ASU 2019-12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adoption [true false]		true
Accounting standards adopted date		Jan. 1, 2021
Change in accounting principle, accounting standards update, immaterial effect [true false]		true
RSU's [Member]
Summary Of Significant Accounting Policies [Line Items]
Vesting term		4 years
Performance Based RSUs [Member]
Summary Of Significant Accounting Policies [Line Items]
Dividend Yield		0.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		3 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of property and equipment		5 years
Lease term		12 months
2.75% Convertible Senior Notes due 2025 [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument due year		2025	2025

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail 1)	Dec. 31, 2021
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-01-01
Summary Of Significant Accounting Policies [Line Items]
Unsatisfied performance obligations period	1 year

Revenue - Summary of Revenue by

Revenue - Summary of Revenue by Geography on Billing Address of Customer (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation Of Revenue [Line Items]
Total revenue	$ 386,905	$ 362,048	$ 390,255
United States [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	326,216	311,873	326,012
International [Member]
Disaggregation Of Revenue [Line Items]
Total revenue	$ 60,689	$ 50,175	$ 64,243

Revenue - Schedule of Revenue b

Revenue - Schedule of Revenue by Major Customers by Geographic Area (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenue [Member] | Geographic Concentration Risk [Member] | United States [Member]
Concentration Risk [Line Items]
Revenue	84.00%	86.00%	84.00%

Revenue - Additional Informatio

Revenue - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)Customer	Dec. 31, 2020USD ($)Customer	Dec. 31, 2019USD ($)Customer
Disaggregation Of Revenue [Line Items]
Revenue | $	$ 386,905	$ 362,048	$ 390,255
Painful Diabetic Neuropathy [Member]
Disaggregation Of Revenue [Line Items]
Revenue | $	$ 5,700
Major Customers [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Disaggregation Of Revenue [Line Items]
Concentration risk, percentage	10.00%	10.00%	10.00%
Number of customers accounted 10% or more concentration risk | Customer	0	0	0
Major Customers [Member] | Credit Concentration Risk [Member] | Accounts Receivable [Member]
Disaggregation Of Revenue [Line Items]
Concentration risk, percentage	10.00%	10.00%
Number of customers accounted 10% or more concentration risk | Customer	0	0

Leases - Additional Information

Leases - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021
Lessee Lease Description [Line Items]
Existence of option to extend the lease	true
Option to extend the lease term, description	As of December 31, 2021, the Company has leases with remaining terms of 3 year to 10 years, some of which may include options to extend the lease term for up to 5 years.
Minimum [Member]
Lessee Lease Description [Line Items]
Operating lease, remaining term	3 years
Maximum [Member]
Lessee Lease Description [Line Items]
Operating lease, remaining term	10 years
Options to extend the lease term	5 years

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Lease Terms and Discounts Rates (Detail)	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted-average remaining lease term	4 years 2 months 12 days	4 years 3 months 25 days
Weighted-average discount rate	7.00%	7.00%

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
2022	$ 5,720
2023	6,019
2024	6,201
2025	2,849
2026	405
Thereafter	1,979
Total lease payments	23,173
Less: Interest	(3,183)
Present value of lease liabilities	$ 19,990	$ 20,565

Leases - Supplemental Lease Cos

Leases - Supplemental Lease Cost Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Operating lease cost	$ 5,243	$ 4,936

Leases - Summary of Operating L

Leases - Summary of Operating Lease Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Leases:
Operating lease assets	$ 17,577	$ 18,142
Other current liabilities	$ 4,588	$ 3,876
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherCurrentLiabilitiesMember	us-gaap:OtherCurrentLiabilitiesMember
Long term operating lease liabilities	$ 15,402	$ 16,689
Total operating lease liabilities	$ 19,990	$ 20,565

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Lease (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flow from operating leases	$ 5,253	$ 4,923

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2021	Dec. 31, 2020
1.75% Convertible Senior Notes due 2021 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate	1.75%		1.75%
Debt instrument due year	2021	2021	2021
Fair value of notes			$ 312.8
2.75% Convertible Senior Notes due 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt instrument interest rate		2.75%	2.75%
Debt instrument due year		2025	2025
Fair value of notes		$ 212	$ 348.1
Fair Value Measurements Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net asset value of market funds		$ 1

Fair Value Measurements - Finan

Fair Value Measurements - Financial Instruments Measured at Fair Value on Recurring Basis (Detail) - Fair Value Measurements Recurring [Member] - USD ($) $ in Thousands		Dec. 31, 2021		Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		$ 341,887		$ 559,646
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		207,114		46,347
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		134,773		513,299
Money Market Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[1]	9,562		16,273
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[1]	9,562		16,273
Agency Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	42,538		210,302
Agency Bonds [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	42,538		210,302
Commercial Paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	61,884		277,602
Commercial Paper [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	61,884		277,602
Corporate Notes [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		30,351	[3]	25,395	[2]
Corporate Notes [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets		30,351	[3]	25,395	[2]
Treasury Bonds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	197,552		30,074
Treasury Bonds [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	[2]	$ 197,552		$ 30,074
[1]	Included in cash and cash equivalents on the consolidated balance sheets.
[2]	Included in short-term investments on the consolidated balance sheets.
[3]	Included in either cash and cash equivalents or short-term investments on the consolidated balance sheets

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Gross Unrealized Gains and Unrealized Losses of Investment Securities Excluding Investments in Money Market Funds (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 332,692	$ 543,246
Gross Unrealized Holding Gains	4	152
Gross Unrealized Holding Losses	(371)	(25)
Aggregate Fair Value	332,325	543,373
Agency Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,546	210,225
Gross Unrealized Holding Gains		79
Gross Unrealized Holding Losses	(8)	(2)
Aggregate Fair Value	42,538	210,302
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	61,886	277,593
Gross Unrealized Holding Gains	2	23
Gross Unrealized Holding Losses	(4)	(14)
Aggregate Fair Value	61,884	277,602
Corporate Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,371	25,364
Gross Unrealized Holding Gains		40
Gross Unrealized Holding Losses	(20)	(9)
Aggregate Fair Value	30,351	25,395
Treasury Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	197,889	30,064
Gross Unrealized Holding Gains	2	10
Gross Unrealized Holding Losses	(339)
Aggregate Fair Value	$ 197,552	$ 30,074

Balance Sheet Components - Su_2

Balance Sheet Components - Summary of Contractual Maturities of Investment Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Investments Debt And Equity Securities [Abstract]
Amortized Cost, Amounts maturing within one year	$ 305,844
Amortized Cost, Amounts maturing after one year through five years	26,848
Amortized Cost	332,692	$ 543,246
Fair Value, Amounts maturing within one year	305,535
Fair Value, Amounts after one year through five years	26,790
Fair Value, Total investment securities	$ 332,325	$ 543,373

Balance Sheet Components - Comp

Balance Sheet Components - Components of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 50,160	$ 34,405
Finished goods	43,357	48,891
Total inventories	$ 93,517	$ 83,296

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Write down of inventory	$ 4,300	$ 5,400	$ 1,600
Property Plant And Equipment [Abstract]
Depreciation and amortization expense	4,882	4,794	$ 4,563
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash	606	606
Certificates of Deposit [Member]
Restricted Cash and Cash Equivalents [Abstract]
Restricted cash	$ 600	$ 600

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 43,319	$ 31,304
Less: Accumulated depreciation and amortization	(22,655)	(17,773)
Property and equipment, net	20,664	13,531
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	8,722	7,072
Computer Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	16,349	12,671
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	4,215	3,918
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	10,316	4,289
Construction in Process [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 3,717	$ 3,354

Balance Sheet Components - Su_3

Balance Sheet Components - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Payables And Accruals [Abstract]
Accrued payroll and related expenses	$ 30,957	$ 30,971
Accrued professional fees	6,547	2,101
Accrued taxes	1,074	1,191
Accrued clinical and research expenses	305	668
Accrued interest	1,305	1,548
Accrued warranty	664	699	$ 1,178
Accrued other	4,665	6,127
Total accrued liabilities	$ 45,517	$ 43,305

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)

Nov. 01, 2021USD ($)

Oct. 31, 2021

Aug. 31, 2020USD ($)ft²

Apr. 30, 2020shares

Jul. 31, 2017USD ($)

Feb. 28, 2017USD ($)

Dec. 31, 2016USD ($)ft²

Mar. 31, 2015USD ($)ft²

Nov. 30, 2014USD ($)shares

Dec. 31, 2021USD ($)

Dec. 31, 2020USD ($)

Dec. 31, 2019USD ($)ConvertibleNote

Apr. 27, 2018Patent

Dec. 09, 2016Patent

Other Commitments [Line Items]

Standard product warranty, description

limited one- to five-year warranty

Retainer fees

$ 47,665,000

$ 45,600,000

$ 59,017,000

Common stock, shares issued | shares

1,868,750

Contingent consideration payment secured by convertible notes

8,500,000

Number of secured convertible notes | ConvertibleNote

2

Secured convertible note, measured at amortized cost

$ 7,900,000

Value of certain rights measured at cost

1,000,000

Contingent consideration expenses net secured by convertible notes

400,000

Contingent liabilities

0

0

Boston Scientific Corporation [Member]

Other Commitments [Line Items]

Patent infringement lawsuit allegation against number of patents | Patent

9

10

Amount awarded by jury

$ 20,000,000

Indemnification Agreement [Member]

Other Commitments [Line Items]

Contingent liabilities

0

Patent Infringement [Member]

Other Commitments [Line Items]

Contingent liabilities

20,000,000

Service Agreement [Member]

Other Commitments [Line Items]

2021

2,500,000

2022

2,500,000

2023

2,500,000

2024

2,500,000

Licensing Agreements [Member]

Other Commitments [Line Items]

Annual royalty payment

$ 0

3,100,000

$ 3,200,000

License agreement commitment amount

$ 100,000

License agreement expiration year

2022

Licensing Agreements [Member] | Mayo And VGL [Member]

Other Commitments [Line Items]

License agreement, terms

The agreement will terminate upon the last to expire patent application, unless terminated earlier. The agreement can be terminated any time after three years from March 2006 by Mayo or VGL.

Licensing Agreements [Member] | Mayo Foundation [Member]

Other Commitments [Line Items]

Retainer fees

$ 40,000

Common stock, shares issued | shares

20,833

Noncash research and development expense

$ 500,000

Licensing Agreements [Member] | Mayo Foundation [Member] | Minimum [Member]

Other Commitments [Line Items]

Annual royalty payment

200,000

Supply Agreements [Member]

Other Commitments [Line Items]

Purchase commitment, amount due

$ 900,000

0

Purchase commitments for inventory related charge

$ 3,600,000

Costa Rica [Member]

Other Commitments [Line Items]

Lease agreement, commencement period

2020-08

Area of office space | ft²

35,411

Lease agreement, effective date

Apr. 30, 2021

Lease agreement, expiration period

2031-06

Lease agreement, lease expense

$ 3,900,000

Redwood Office Agreement [Member]

Other Commitments [Line Items]

Lease agreement, commencement period

2015-03

Area of office space | ft²

50,740

Lease agreement, effective date

Jun. 30, 2015

Lease agreement, expiration period

2022-05

Lease expense, payment due

$ 2,000,000

Annual lease expense payable in final year of lease term

$ 2,400,000

Redwood Office Agreement Additional Expansion Premises [Member] | Amendment 1 [Member]

Other Commitments [Line Items]

Area of office space | ft²

49,980

Lease expense, payment due

$ 1,200,000

Annual lease expense payable in final year of lease term

$ 2,900,000

Commencement date description

The lease for the Expansion Premises commenced on June 1, 2018.

Lease commencement date

Jun. 1, 2018

Lease agreement, expiration date

May 31, 2025

Non-cancellable Facility Lease [Member]

Other Commitments [Line Items]

Lease agreement, effective date

Mar. 1, 2017

Lease agreement, expiration date

Feb. 28, 2022

Lease agreement, lease expense

$ 400,000

Non-cancellable Facility Lease [Member] | Amendment 1 [Member]

Other Commitments [Line Items]

Lease agreement, expiration date

May 31, 2025

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Activities Related to Warranty Obligations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Commitments And Contingencies Disclosure [Abstract]
Beginning balance	$ 699	$ 1,178
Provision for warranty	2,846	2,150
Utilization	(2,881)	(2,629)
Ending balance	$ 664	$ 699

Long-term Debt - Additional Inf

Long-term Debt - Additional Information (Detail)	Jun. 01, 2021USD ($)shares	Apr. 30, 2020USD ($)d$ / sharesshares	Jun. 30, 2016USD ($)d$ / sharesshares	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Debt Instrument [Line Items]
Proceeds from issuance of warrants					$ 34,933,000
2021 Notes and Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount of convertible senior notes			$ 150,000,000
Debt instrument interest rate			1.75%
Debt instrument due year			2021-06
Additional aggregate principal amount of convertible senior notes			$ 22,500,000
Debt instrument frequency of payment				semi-annually in arrears on June 1 and December 1 of each year, commencing on December 1, 2016
Net proceeds from the debt offering after deducting transaction costs			166,200,000
Convertible notes principal amount			$ 1,000
Convertible notes, shares issued | shares			10.3770
Convertible notes, type of equity security issued				common stock
Convertible notes, conversion price | $ / shares			$ 96.37
Debt instrument convertible, percentage of conversion price			130.00%
Percentage of repurchase price, which is equal to principal amount of convertible notes			100.00%
Number of shares purchased under convertible note hedge transactions | shares			1,800,000
Purchase price of the shares issued under convertible note hedge transactions | $ / shares			$ 96.37
Total cost of the convertible note hedge transactions			$ 45,100,000
Proceeds from issuance of warrants			33,100,000
Net cost of reduction to additional paid-in capital			12,000,000
Debt conversion, converted instrument amount			$ 32,900,000
Debt instrument, effective interest rate			6.29%
Debt issuance costs attributable to the liability and equity component, total amount		$ 6,100,000	$ 6,200,000
Debt issuance costs attributable to the liability component		4,500,000	$ 5,000,000
2021 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Convertible notes, shares issued | shares	682,912
Debt issuance costs attributable to the liability component					542,000
Principal amount	$ 172,500,000				172,500,000
Share received on option exercise | shares	682,916
Holders of warrants associated	$ 0
2021 Notes and Convertible Notes [Member] | Warrant [Member]
Debt Instrument [Line Items]
Number of shares issued for warrants under convertible note hedge transactions | shares			1,800,000
Purchase price of the shares issued under convertible note hedge transactions | $ / shares			$ 127.28
2021 Notes and Convertible Notes [Member] | 130% for Applicable Conversion Price [Member]
Debt Instrument [Line Items]
Debt instrument convertible trading days | d			20
Debt instrument convertible consecutive trading days | d			30
2021 Notes and Convertible Notes [Member] | 98% Applicable Conversion Price [Member]
Debt Instrument [Line Items]
Debt instrument convertible trading days | d			5
Debt instrument convertible consecutive trading days | d			10
2021 Notes and Convertible Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage of closing sale price of common stock			98.00%
2021 Notes and Convertible Notes [Member] | Maximum [Member] | Warrant [Member]
Debt Instrument [Line Items]
Overall conversion price | $ / shares			$ 127.28
2021 Notes and Convertible Notes [Member] | Minimum [Member] | Warrant [Member]
Debt Instrument [Line Items]
Overall conversion price | $ / shares			$ 96.37
2025 Notes and Convertible Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount of convertible senior notes		$ 165,000,000
Debt instrument interest rate		2.75%
Additional aggregate principal amount of convertible senior notes		$ 24,800,000
Debt instrument frequency of payment				semi-annually in arrears on April 1 and October 1 of each year, commencing on October 1, 2020
Net proceeds from the debt offering after deducting transaction costs		183,600,000
Convertible notes principal amount		$ 1,000
Convertible notes, shares issued | shares		9.5238
Convertible notes, type of equity security issued				common stock
Convertible notes, conversion price | $ / shares		$ 105
Debt instrument convertible, percentage of conversion price		130.00%
Percentage of repurchase price, which is equal to principal amount of convertible notes		100.00%
Number of shares purchased under convertible note hedge transactions | shares		1,800,000
Purchase price of the shares issued under convertible note hedge transactions | $ / shares		$ 105
Total cost of the convertible note hedge transactions		$ 52,400,000
Proceeds from issuance of warrants		34,900,000
Net cost of reduction to additional paid-in capital		17,500,000
Debt conversion, converted instrument amount		$ 49,900,000
Debt instrument, effective interest rate		10.20%
Debt instrument due year		2025
Converted Value in Excess of Principal				$ 0
2025 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Debt issuance costs attributable to the liability component				3,361,000	4,060,000
Principal amount				$ 189,750,000	$ 189,750,000
2025 Notes and Convertible Notes [Member] | Warrant [Member]
Debt Instrument [Line Items]
Number of shares issued for warrants under convertible note hedge transactions | shares		1,800,000
Purchase price of the shares issued under convertible note hedge transactions | $ / shares		$ 147
2025 Notes and Convertible Notes [Member] | 130% for Applicable Conversion Price [Member]
Debt Instrument [Line Items]
Debt instrument convertible trading days | d		20
Debt instrument convertible consecutive trading days | d		30
2025 Notes and Convertible Notes [Member] | 98% Applicable Conversion Price [Member]
Debt Instrument [Line Items]
Debt instrument convertible trading days | d		5
Debt instrument convertible consecutive trading days | d		10
2025 Notes and Convertible Notes [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage of closing sale price of common stock		98.00%
2025 Notes and Convertible Notes [Member] | Maximum [Member] | Warrant [Member]
Debt Instrument [Line Items]
Overall conversion price | $ / shares		$ 147
2025 Notes and Convertible Notes [Member] | Minimum [Member] | Warrant [Member]
Debt Instrument [Line Items]
Overall conversion price | $ / shares		$ 105

Long-term Debt - Net Carrying A

Long-term Debt - Net Carrying Amount of Liability Component of Convertible Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Jun. 01, 2021	Dec. 31, 2020	Apr. 30, 2020	Jun. 30, 2016
2021 Notes and Convertible Notes [Member]
Debt Instrument [Line Items]
Unamortized issuance cost				$ (4,500)	$ (5,000)
2021 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Principal		$ 172,500	$ 172,500
Unamortized discount			(3,182)
Unamortized issuance cost			(542)
Net carrying amount			168,776
2025 Notes and Convertible Notes [Member] | Debt, Liability Component [Member]
Debt Instrument [Line Items]
Principal	$ 189,750		189,750
Unamortized discount	(35,079)		(43,919)
Unamortized issuance cost	(3,361)		(4,060)
Net carrying amount	$ 151,310		$ 141,771

Long-term Debt - Net Carrying_2

Long-term Debt - Net Carrying Amount of Equity Component of Convertible Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Apr. 30, 2020
1.75% Convertible Senior Notes due 2021 [Member] | Debt, Equity Component [Member]
Debt Instrument [Line Items]
Debt discount related to value of conversion option		$ 32,945
Debt issuance cost		(1,179)
Net carrying amount		31,766
2025 Notes and Convertible Notes [Member]
Debt Instrument [Line Items]
Net carrying amount			$ 49,900
2025 Notes and Convertible Notes [Member] | Debt, Equity Component [Member]
Debt Instrument [Line Items]
Debt discount related to value of conversion option	$ 49,947	49,947
Debt issuance cost	(1,607)	(1,607)
Net carrying amount	$ 48,340	$ 48,340

Long-term Debt - Interest Expen

Long-term Debt - Interest Expense Recognized Related to Convertible Notes (Detail) - 2021 Notes and 2025 Notes [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Contractual interest expense	$ 6,484	$ 6,860	$ 3,019
Amortization of debt discount	12,023	13,308	6,843
Amortization of debt issuance costs	1,240	1,634	1,063
Total interest expense	$ 19,747	$ 21,802	$ 10,925

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - shares	Nov. 11, 2014	Dec. 31, 2021	Dec. 31, 2020	Nov. 10, 2014
Class of Stock [Line Items]
Convertible preferred stock outstanding		0	0	15,208,048
IPO [Member]
Class of Stock [Line Items]
Convertible preferred stock converted to common stock	15,208,048
Common Stock [Member]
Class of Stock [Line Items]
Common stock shares issued for each convertible preferred stock	1

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Common Stock Reserved for Future Issuance (Detail)	Dec. 31, 2021shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding stock options and awards	1,713,145
Reserved for grants of future stock options and awards	6,078,869
Reserved for employee stock purchase plan	1,567,514
Total common stock reserved for future issuance	9,359,528

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Mar. 31, 2021	Mar. 31, 2019	Oct. 31, 2014	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance				9,359,528
Weighted-average grant-date fair value of options granted						$ 27.91
Fair value of options vested				$ 3,100	$ 6,600	$ 8,300
Employee stock purchase plan offering period			6 months	6 months
Stock-based compensation expense				$ 44,365	42,655	41,697
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option purchase price, percentage of fair value			85.00%
Number of shares available for sale			196,666
Maximum employee subscription rate			15.00%
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense				$ 10,017	5,694	1,991
Performance Stock Units [Member] | CEO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted composite index period		3 years
Performance Stock Units [Member] | Member of Management Team [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted composite index period	3 years
RSU's [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term				4 years
Stock-based compensation expense		$ 1,600		$ 29,234	$ 27,977	$ 26,854
Maximum [Member] | Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognition period of stock based compensation expense		3 years
Maximum [Member] | Performance Stock Units [Member] | CEO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted number of shares granted ratio		350.00%
Maximum [Member] | Performance Stock Units [Member] | Member of Management Team [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted number of shares granted ratio	150.00%
Minimum [Member] | Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognition period of stock based compensation expense		2 years
Minimum [Member] | Performance Stock Units [Member] | CEO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted number of shares granted ratio		0.00%
Minimum [Member] | Performance Stock Units [Member] | Member of Management Team [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Targeted number of shares granted ratio	0.00%
2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional awards authorized under plan				0
2014 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance			1,854,166
Plan modification description				The number of shares initially reserved for issuance under the 2014 Plan is subject to increase by (i) the number of shares represented by awards outstanding under the 2007 Plan that are forfeited or lapse unexercised and which following the pricing date are not issued under the 2007 Plan, and (ii) an annual increase on January 1 of each year.
2014 Plan [Member] | ISO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shareholder granted option				10.00%
2014 Plan [Member] | NSO [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shareholder granted option				10.00%
2014 Plan [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term				4 years
2014 Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options expiration period				10 years
Option purchase price, percentage of fair value				110.00%
2014 Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option purchase price, percentage of fair value				100.00%

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Shares Available for Grant (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Beginning balances	4,600,181	3,403,006	2,980,762
Shares Available for Grant, Additional shares reserved	1,383,322	1,261,774	1,210,541
Shares Available for Grant, Allowance for PSU for over performance	(24,830)	(43,966)	(277,778)
Shares Available for Grant, Shares forfeited for tax	58,787	62,782	38,696
Shares Available for Grant, Ending balances	5,732,295	4,600,181	3,403,006
Employee Stock Option, RSUs and PSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Available for Grant, Options and other than options granted	(425,266)	(341,901)	(1,077,178)
Shares Available for Grant, Options and other than options forfeited or cancelled	140,101	258,486	527,963

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Activity under Stock Plans (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Exercise Price And Additional Disclosures [Abstract]
Number of Options, Outstanding Beginning balances	813,150	1,646,185	2,529,740
Number of Options, Options granted			244,075
Number of Options, Options exercised	(90,582)	(756,797)	(828,722)
Number of Options, Options cancelled	(21,914)	(76,238)	(298,908)
Number of Options, Outstanding Ending balances	700,654	813,150	1,646,185	2,529,740
Number of Options, Options exercisable	599,295
Number of Options, Options vested, exercisable or expected to vest	696,003
Weighted Average Exercise Price, Beginning balances	$ 54.69	$ 50.80	$ 46.72
Weighted Average Exercise Price, Options granted			56.71
Weighted Average Exercise Price, Options exercised	47.82	45.75	34.52
Weighted Average Exercise Price, Options cancelled	43.52	59.38	66.22
Weighted Average Exercise Price, Ending balances	55.93	$ 54.69	$ 50.80	$ 46.72
Weighted Average Exercise Price, Options exercisable	56.06
Weighted Average Exercise Price, Options vested, exercisable or expected to vest	$ 55.92
Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 9 months 18 days	5 years 10 months 24 days	6 years 3 months 18 days	6 years 8 months 12 days
Options exercisable, Weighted-Average Remaining Contractual Term	4 years 4 months 24 days
Options vested, exercisable or expected to vest, Weighted Average Remaining Contractual Term	4 years 9 months 18 days
Options Outstanding, Aggregate Intrinsic Value	$ 18,287	$ 96,286	$ 109,870	$ 21,866
Options exercised, Aggregate Intrinsic Value	6,948	$ 62,367	$ 42,695
Options exercisable, Aggregate Intrinsic Value	15,656
Options vested, exercisable or expected to vest, Aggregate Intrinsic Value	$ 18,173

Stock-Based Compensation - Su_4

Stock-Based Compensation - Summary of Options Outstanding and Vested Under Stock Plans by Exercise Price (Detail)	12 Months Ended
	Dec. 31, 2021$ / sharesshares
$3.60 - $36.55 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	$ 3.60
Options Outstanding, Exercise Price Upper Range Limit	$ 36.55
Number of Options Outstanding | shares	116,179
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	3 years 1 month 24 days
Options Outstanding, Weighted Average Exercise Price	$ 19.18
Options Vested, Number Exercisable | shares	111,929
Options Vested, Weighted Average Exercise Price	$ 18.52
$38.79 - $45.04 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	38.79
Options Outstanding, Exercise Price Upper Range Limit	$ 45.04
Number of Options Outstanding | shares	114,032
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	5 years 6 months 7 days
Options Outstanding, Weighted Average Exercise Price	$ 47.12
Options Vested, Number Exercisable | shares	94,094
Options Vested, Weighted Average Exercise Price	$ 42.08
$45.07 - $63.23 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	45.07
Options Outstanding, Exercise Price Upper Range Limit	$ 63.23
Number of Options Outstanding | shares	156,883
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	4 years 5 months 23 days
Options Outstanding, Weighted Average Exercise Price	$ 57.56
Options Vested, Number Exercisable | shares	129,344
Options Vested, Weighted Average Exercise Price	$ 59.12
$63.39 - $64.95 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	63.39
Options Outstanding, Exercise Price Upper Range Limit	$ 64.95
Number of Options Outstanding | shares	141,004
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	6 years 11 months 8 days
Options Outstanding, Weighted Average Exercise Price	$ 64.28
Options Vested, Number Exercisable | shares	91,835
Options Vested, Weighted Average Exercise Price	$ 64.21
$65.51 - $87.62 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	65.51
Options Outstanding, Exercise Price Upper Range Limit	$ 87.62
Number of Options Outstanding | shares	152,556
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	3 years 11 months 12 days
Options Outstanding, Weighted Average Exercise Price	$ 79.37
Options Vested, Number Exercisable | shares	152,093
Options Vested, Weighted Average Exercise Price	$ 79.36
$97.52 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price	$ 97.52
Number of Options Outstanding | shares	20,000
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	4 years 7 months 13 days
Options Outstanding, Weighted Average Exercise Price	$ 97.52
Options Vested, Number Exercisable | shares	20,000
Options Vested, Weighted Average Exercise Price	$ 97.52
$3.60 - $97.52 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Options Outstanding, Exercise Price Lower Range Limit	3.60
Options Outstanding, Exercise Price Upper Range Limit	$ 97.52
Number of Options Outstanding | shares	700,654
Options Outstanding, Weighted Average Remaining Contractual Life (in Years)	4 years 9 months 21 days
Options Outstanding, Weighted Average Exercise Price	$ 55.93
Options Vested, Number Exercisable | shares	599,295
Options Vested, Weighted Average Exercise Price	$ 56.06

Stock-Based Compensation - Su_5

Stock-Based Compensation - Summary of Restricted Stock Units Under Stock Plan (Detail) - Restricted Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units, Outstanding Beginning Balance	852,977	1,177,221	1,002,161
Number of Restricted Stock Units, Restricted stock granted	368,230	252,703	721,992
Number of Restricted Stock Units, Restricted stock released	(346,602)	(395,971)	(321,858)
Number of Restricted Stock Units, Restricted stock cancelled	(110,799)	(180,976)	(225,074)
Number of Restricted Stock Units, Outstanding Ending Balance	763,806	852,977	1,177,221
Number of Restricted Stock Units, Restricted stock expected to vest	696,348
Weighted Average Grant Date Fair Value Outstanding, Beginning Balance	$ 79.87	$ 64.70	$ 72.55
Weighted Average Grant Date Fair Value, Granted	146.64	123.31	58.37
Weighted Average Grant Date Fair Value, Released	76.26	66.42	70.89
Weighted Average Grant Date Fair Value, Cancelled	98.76	71.26	70.51
Weighted Average Grant Date Fair Value Outstanding, Ending Balance	110.96	$ 79.87	$ 64.70
Weighted Average Grant Date Fair Value, Restricted stock expected to vest	$ 109.78
Aggregate Intrinsic Value Outstanding	$ 61,922	$ 147,650	$ 138,371	$ 38,974
Aggregate Intrinsic Value, Released	22,902	$ 23,789	$ 4,064
Aggregate Intrinsic Value, Expected to vest	$ 56,453

Stock-Based Compensation - Su_6

Stock-Based Compensation - Summary of Performance Stock Units Under Stock Plan (Detail) - Performance Stock Units [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Restricted Stock Units, Outstanding Beginning Balance	199,037	111,111	7,962
Number of Restricted Stock Units, PSU granted	57,036	89,198	111,111
Number of Restricted Stock Units, PSU released			(3,981)
Number of Restricted Stock Units, PSU cancelled	(7,388)	(1,272)	(3,981)
Number of Restricted Stock Units, Outstanding Ending Balance	248,685	199,037	111,111
Number of Restricted Stock Units, PSU expected to vest	247,815
Weighted Average Grant Date Fair Value Outstanding, Beginning Balance	$ 94.20	$ 67.29	$ 54.50
Weighted Average Grant Date Fair Value, PSU Granted	183.20	128.71	67.29
Weighted Average Grant Date Fair Value, PSU Released			54.50
Weighted Average Grant Date Fair Value, PSU Cancelled	136.77	125.27	54.50
Weighted Average Grant Date Fair Value Outstanding, Ending Balance	113.35	$ 94.20	$ 67.29
Weighted Average Grant Date Fair Value, PSU expected to vest	$ 113.22
Aggregate Intrinsic Value PSU Outstanding	$ 20,161	$ 34,453	$ 13,060	$ 310
Aggregate Intrinsic Value, PSU Expected to vest	$ 20,090

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Employee Stock Purchase Plan Activity (Detail) - ESPP [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved	235,590	315,443	302,635
Shares issued	65,197	79,967	164,960
Shares available for future issuance	1,567,514	1,397,121	1,161,645
Employee contributions for shares issued	$ 6,849	$ 7,513	$ 6,544

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Fair Value of Employee Stock Options Using Black-Scholes Option Valuation Model (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)			5 years 8 months 12 days
Expected volatility, minimum			51.00%
Expected volatility, maximum			52.00%
Risk-free interest rate, minimum			1.40%
Risk-free interest rate, maximum			2.60%
Dividend Yield			0.00%
ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Expected volatility, minimum	36.00%	39.00%	48.00%
Expected volatility, maximum	49.00%	68.00%	61.00%
Risk-free interest rate	0.10%
Risk-free interest rate, minimum		0.10%	1.60%
Risk-free interest rate, maximum		0.20%	2.40%
Dividend Yield	0.00%	0.00%	0.00%

Stock-Based Compensation - Sc_3

Stock-Based Compensation - Schedule of Fair Value of Performance Based RUSs based on Monte Carlo Simulation Model (Detail) - Performance Stock Units [Member]	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Index volatility			36.00%
Company volatility			45.00%
Risk-free interest rate			2.40%
Correlation with index			0.28%
Dividend Yield	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Index volatility	51.00%	44.00%
Company volatility	49.00%	57.00%
Risk-free interest rate	0.10%	0.10%
Correlation with index	0.32%	0.38%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Index volatility	53.00%	51.00%
Company volatility	54.00%	59.00%
Risk-free interest rate	0.30%	0.20%
Correlation with index	0.35%	0.41%

Stock-Based Compensation - Su_7

Stock-Based Compensation - Summary of Stock-Based Compensation Expense by Line Items in Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 44,365	$ 42,655	$ 41,697
Cost of Revenue [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,637	2,433	3,061
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	6,455	6,141	6,323
Selling, General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 36,273	$ 34,081	$ 32,313

Stock-Based Compensation - Su_8

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense		$ 44,365	$ 42,655	$ 41,697
Stock Options [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense		2,997	6,289	10,312
Restricted Stock Units [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,600	29,234	27,977	26,854
Performance Stock Units [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense		10,017	5,694	1,991
Employee Stock Purchase Plan [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense		$ 2,117	$ 2,695	$ 2,540

Stock-Based Compensation - Su_9

Stock-Based Compensation - Summary of Stock-Based Compensation Expense Not Yet Recognized (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 2,597
Weighted-Average Amortization Period (in years)	1 year 2 months 12 days
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 61,107
Weighted-Average Amortization Period (in years)	2 years 1 month 6 days
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 10,389
Weighted-Average Amortization Period (in years)	8 months 12 days
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized Compensation	$ 1,219
Weighted-Average Amortization Period (in years)	4 months 24 days

Income Taxes - Components of Lo

Income Taxes - Components of Loss before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Domestic	$ (129,135)	$ (83,893)	$ (106,010)
Foreign	(1,691)	1,696	3,923
Loss before income taxes	$ (130,826)	$ (82,197)	$ (102,087)

Income Taxes - Components of Ex

Income Taxes - Components of Expense/(Benefit) for Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current:
Federal			$ (103)
State	$ 244	$ 188	187
Foreign	585	656	1,644
Total current income tax expense / (benefit)	829	844	1,728
Deferred:
Foreign	(295)	24	(129)
Total deferred income tax expense / (benefit)	(295)	24	(129)
Total income tax expense / (benefit)	$ 534	$ 868	$ 1,599

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense by Applying Statutory Federal Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Tax at statutory federal rate	21.00%	21.00%	21.00%
State tax, net of federal benefit	(0.20%)	(0.20%)	(0.10%)
Foreign rate differential	(0.50%)	(0.40%)	(0.70%)
Tax credits	3.00%	1.40%	3.00%
Stock-based compensation	(0.20%)	9.80%	3.80%
Change in valuation allowance	(23.30%)	(33.60%)	(26.40%)
Other	(0.20%)	0.90%	(2.20%)
Total	(0.40%)	(1.10%)	(1.60%)

Income Taxes - Tax Effects of T

Income Taxes - Tax Effects of Temporary Differences and Carryforwards That Give Rise to Significant Portions of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 154,614	$ 127,347
Tax credits	25,087	18,919
Depreciation	650	662
Stock-based compensation	6,969	7,390
Accruals and reserves	13,404	9,531
Right of use asset	4,225	5,055
Other	1,130	869
Gross deferred tax assets	206,079	169,773
Valuation allowance	(201,088)	(164,278)
Deferred tax assets	4,991	5,495
Lease liabilities	(3,660)	(4,459)
Deferred tax liabilities	(3,660)	(4,459)
Net deferred tax assets	$ 1,331	$ 1,036

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Taxes [Line Items]
Increase in valuation allowance	$ 36,800	$ 32,500
Net operating loss carryforward	54,300
Unrecognized tax benefits	10,430	8,220	$ 7,383	$ 5,200
Accrued interest and penalties	200	$ 100	$ 100
Research and Development Credit Carryforwards [Member] | California state [Member]
Income Taxes [Line Items]
Tax credit carry forwards	13,900
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforward	$ 588,400			$ 329,400
Net operating loss expiration date	2026
Federal [Member] | Research and Development Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credit carry forwards	$ 20,500
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carryforward	$ 336,500
Net operating loss expiration date	2022

Income Taxes - Summary of Unrec

Income Taxes - Summary of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Beginning balance	$ 8,220	$ 7,383	$ 5,200
Increases related to current year tax provisions	1,412	891	1,611
Increases related to prior year tax provisions	860		572
Decreases related to prior year tax provisions	(62)	(54)
Ending balance	$ 10,430	$ 8,220	$ 7,383

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share [Abstract]
Net loss	$ (131,360)	$ (83,065)	$ (103,686)
Weighted average number of common shares used to compute basic and diluted net loss per share	34,823,258	33,677,641	30,803,872
Net loss per share, basic and diluted	$ (3.77)	$ (2.47)	$ (3.37)

Net Loss Per Share - Additional

Net Loss Per Share - Additional Information (Detail) $ / shares in Units, $ in Thousands	Dec. 31, 2021USD ($)$ / shares
Earnings Per Share Diluted [Line Items]
Notes outstanding | $	$ 0
2025 Notes and Convertible Notes [Member]
Earnings Per Share Diluted [Line Items]
Convertible notes, conversion price | $ / shares	$ 105

Net Loss Per Share - Computat_2

Net Loss Per Share - Computation of Potentially Dilutive Securities Outstanding Excluded from Computation of Diluted Shares (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	5,327,427	9,059,512	6,514,583
Unreleased Restricted and Performance Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	1,012,491	1,052,014	1,288,332
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	700,654	813,150	1,646,185
Convertible Senior Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	1,807,141	3,597,174	1,790,033
Warrants Related to the Issuance of Convertible Senior Notes [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities excluded from computation of diluted shares outstanding	1,807,141	3,597,174	1,790,033

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Compensation And Retirement Disclosure [Abstract]
Expense for matching contributions	$ 2.9	$ 2.6	$ 3.1