Tandem Diabetes Care (TNDM) 10-Q 4 Nov 19 2019 Q3 Quarterly report Financial data

Cover Page

Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 30, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-36189
Entity Registrant Name	Tandem Diabetes Care, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-4327508
Entity Address, Address Line One	11075 Roselle Street
Entity Address, Postal Zip Code	92121
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
City Area Code	858
Local Phone Number	366-6900
Title of 12(b) Security	Common Stock, par value $0.001 per share
Trading Symbol	TNDM
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		59,092,861
Amendment Flag	false
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Central Index Key	0001438133
Current Fiscal Year End Date	--12-31

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 46,060	$ 41,826
Short-term investments	110,887	87,201
Accounts receivable, net	45,325	35,193
Inventories, net	40,732	19,896
Prepaid and other current assets	3,594	3,769
Total current assets	246,598	187,885
Property and equipment, net	28,072	17,151
Operating lease right-of-use assets	16,577
Other long-term assets	515	128
Total assets	292,647	206,294
Current liabilities:
Accounts payable	16,314	6,824
Accrued expenses	7,978	3,930
Employee-related liabilities	28,207	24,030
Deferred revenue	8,187
Deferred revenue		4,600
Common stock warrants	23,283	17,926
Operating lease liabilities	5,951
Other current liabilities	10,346	8,978
Total current liabilities	100,266	66,288
Deferred rent - long-term		3,799
Operating lease liabilities - long-term	15,258
Other long-term liabilities	10,129	4,932
Total liabilities	125,653	75,019
Commitments and contingencies (Note 9)
Stockholders’ equity:
Common stock, $0.001 par value; 200,000 shares authorized, 59,029 and 57,554 shares issued and outstanding at September 30, 2019 (unaudited) and December 31, 2018, respectively.	59	57
Additional paid-in capital	794,324	731,306
Accumulated other comprehensive income (loss)	91	(13)
Accumulated deficit	(627,480)	(600,075)
Total stockholders’ equity	166,994	131,275
Total liabilities and stockholders’ equity	292,647	206,294
Patents
Current assets:
Patents, net	$ 885	$ 1,130

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Common stock, par value (in usd per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	59,029,000	57,554,000
Common stock, shares outstanding (in shares)	59,029,000	57,554,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Sales	$ 94,657	$ 46,264	$ 253,907	$ 107,667
Cost of sales	43,974	24,468	119,967	59,381
Gross profit	50,683	21,796	133,940	48,286
Operating expenses:
Selling, general and administrative	44,649	29,506	120,173	73,048
Research and development	12,038	7,999	32,632	20,430
Total operating expenses	56,687	37,505	152,805	93,478
Operating loss	(6,004)	(15,709)	(18,865)	(45,192)
Other income (expense), net:
Interest and other income	914	443	2,457	833
Interest and other expense	(60)	(1,401)	(76)	(7,585)
Loss on extinguishment of debt	0	(5,313)	0	(5,313)
Change in fair value of stock warrants	2,321	(12,265)	(10,849)	(69,042)
Total other income (expense), net	3,175	(18,536)	(8,468)	(81,107)
Loss before income taxes	(2,829)	(34,245)	(27,333)	(126,299)
Income tax expense	72	0	72	0
Net loss	(2,901)	(34,245)	(27,405)	(126,299)
Other comprehensive loss:
Unrealized gain (loss) on short-term investments	(60)	(19)	91	(13)
Foreign currency translation gain (loss)	(11)	0	13	0
Comprehensive loss	$ (2,972)	$ (34,264)	$ (27,301)	$ (126,312)
Net loss per share, basic (in dollars per share)	$ (0.05)	$ (0.62)	$ (0.47)	$ (2.81)
Net loss per share, diluted (in dollars per share)	$ (0.09)	$ (0.62)	$ (0.47)	$ (2.81)
Weighted average shares used to compute basic net loss per share (in shares)	58,801	55,615	58,268	44,993
Weighted average shares used to compute diluted net loss per share (in shares)	59,196	55,615	58,268	44,993

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017	$ (29,149)	$ 10	$ 448,455	$ 0	$ (477,614)
Beginning balance (shares) at Dec. 31, 2017		10,119,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options	470		470
Exercise of stock options (in shares)		32,000
Exercise of common stock warrants	29,560	$ 8	29,552
Exercise of common stock warrants (shares)		8,598,000
Fair value of common stock warrants at time of exercise	53,831		53,831
Stock-based compensation	13,950		13,950
Foreign currency translation gain (loss)	0
Unrealized gain (loss) on short-term investments	(13)			(13)
Net loss	(126,299)				(126,299)
Adjustment to retained earnings from adoption of ASC 606	150				150
Issuance of common stock in public offering, net of underwriter’s discount and offering costs	172,929	$ 39	172,890
Issuance of common stock in public offering, net of underwriter’s discount and offering costs (shares)		38,535,000
Share-based compensation (shares)		80,000
Ending balance at Sep. 30, 2018	115,429	$ 57	719,148	(13)	(603,763)
Ending balance (shares) at Sep. 30, 2018		57,364,000
Beginning balance at Dec. 31, 2017	(29,149)	$ 10	448,455	0	(477,614)
Beginning balance (shares) at Dec. 31, 2017		10,119,000
Ending balance at Dec. 31, 2018	131,275	$ 57	731,306	(13)	(600,075)
Ending balance (shares) at Dec. 31, 2018		57,554,000
Beginning balance at Jun. 30, 2018	26,004	$ 53	595,463	6	(569,518)
Beginning balance (shares) at Jun. 30, 2018		53,186,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options	467		467
Exercise of stock options (in shares)		31,000
Exercise of common stock warrants	393	$ 0	393
Exercise of common stock warrants (shares)		112,000
Fair value of common stock warrants at time of exercise	3,913		3,913
Stock-based compensation	9,996		9,996
Foreign currency translation gain (loss)	0
Unrealized gain (loss) on short-term investments	(19)			(19)
Net loss	(34,245)				(34,245)
Issuance of common stock in public offering, net of underwriter’s discount and offering costs	108,920	$ 4	108,916
Issuance of common stock in public offering, net of underwriter’s discount and offering costs (shares)		4,035,000
Ending balance at Sep. 30, 2018	115,429	$ 57	719,148	(13)	(603,763)
Ending balance (shares) at Sep. 30, 2018		57,364,000
Beginning balance at Dec. 31, 2018	131,275	$ 57	731,306	(13)	(600,075)
Beginning balance (shares) at Dec. 31, 2018		57,554,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options	14,512	$ 2	14,510
Exercise of stock options (in shares)		1,214,000
Exercise of common stock warrants	326		326
Exercise of common stock warrants (shares)		93,000
Issuance of common stock for Employee Stock Purchase Plan	2,951		2,951
Issuance of common stock for Employee Stock Purchase Plan (shares)		168,000
Fair value of common stock warrants at time of exercise	5,492		5,492
Stock-based compensation	39,739		39,739
Foreign currency translation gain (loss)	13			13
Unrealized gain (loss) on short-term investments	91			91
Net loss	(27,405)				(27,405)
Ending balance at Sep. 30, 2019	166,994	$ 59	794,324	91	(627,480)
Ending balance (shares) at Sep. 30, 2019		59,029,000
Beginning balance at Jun. 30, 2019	145,345	$ 58	769,704	162	(624,579)
Beginning balance (shares) at Jun. 30, 2019		58,589,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options	7,034	$ 1	7,033
Exercise of stock options (in shares)		440,000
Fair value of common stock warrants at time of exercise	13		13
Stock-based compensation	17,574		17,574
Foreign currency translation gain (loss)	(11)			(11)
Unrealized gain (loss) on short-term investments	(60)			(60)
Net loss	(2,901)				(2,901)
Ending balance at Sep. 30, 2019	$ 166,994	$ 59	$ 794,324	$ 91	$ (627,480)
Ending balance (shares) at Sep. 30, 2019		59,029,000

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities
Net loss	$ (27,405)	$ (126,299)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization expense	4,430	4,353
Interest expense related to amortization of debt discount and debt issuance costs	0	1,721
Provision for allowance for doubtful accounts	1,468	1,017
Provision for inventories reserve	1,508	397
Change in fair value of common stock warrants	10,849	69,042
Amortization of premium (discount) on short-term investments	(302)	783
Stock-based compensation expense	39,386	13,427
Loss on extinguishment of debt	0	5,313
Other	42	155
Changes in operating assets and liabilities:
Accounts receivable, net	(11,588)	(1,913)
Inventories, net	(21,990)	2,752
Prepaid and other current assets	(17)	(823)
Other long-term assets	(387)	(39)
Accounts payable	7,131	1,083
Accrued expenses	4,045	1,098
Employee-related liabilities	4,173	2,741
Deferred revenue	3,587	1,178
Other current liabilities	2,335	1,100
Deferred rent	0	(571)
Other long-term liabilities	5,198	1,033
Net cash provided by (used in) operating activities	22,463	(22,452)
Investing activities
Purchases of short-term investments	(126,307)	(100,550)
Proceeds from maturities of short-term investments	96,495	18,500
Proceeds from sales of short-term investments	6,550	0
Purchases of property and equipment	(12,792)	(2,098)
Net cash used in investing activities	(36,054)	(84,148)
Financing activities
Principal payments on notes payable	0	(87,711)
Proceeds from public offering, net of offering costs	0	172,929
Proceeds from exercise of common stock warrants	327	29,536
Proceeds from issuance of common stock under Company stock plans	17,462	473
Net cash provided by financing activities	17,789	115,227
Effect of foreign exchange rate changes on cash	36	0
Net increase in cash and cash equivalents and restricted cash	4,234	8,627
Cash and cash equivalents and restricted cash at beginning of period	41,826	23,700
Cash and cash equivalents at end of period	46,060	32,327
Supplemental disclosures of cash flow information
Interest paid	0	5,841
Supplemental schedule of non-cash investing and financing activities
Right-of-use assets obtained in exchange for operating lease obligations	11,445	0
Property and equipment included in accounts payable	$ 2,484	$ 57

Organization and Basis of Prese

Organization and Basis of Presentation	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation The Company Tandem Diabetes Care, Inc. is a medical device company with an innovative approach to the design, development and commercialization of products for people with insulin-dependent diabetes. The Company is incorporated in the state of Delaware. Unless the context requires otherwise, the terms the “Company” or “Tandem” refer to Tandem Diabetes Care, Inc., together with its wholly-owned subsidiary in Canada. The Company manufactures, sells and supports insulin pump products that are designed to address the evolving needs and preferences of differentiated segments of the insulin-dependent diabetes market. The Company’s manufacturing, sales and support activities principally focus on the t:slim X2 Insulin Delivery System (t:slim X2), the Company’s flagship pump platform which is capable of remote feature updates and is designed to display continuous glucose monitoring (CGM) sensor information directly on the pump home screen. The Company’s insulin pump products are compatible with the Tandem Device Updater, a Mac and PC-compatible tool for the remote update of the Company's insulin pump software. The Company’s insulin pump products are generally considered durable medical equipment and have an expected lifespan of at least four years . In addition to insulin pumps, the Company sells disposable products that are used together with the pumps and are replaced every few days, including cartridges for storing and delivering insulin, and infusion sets that connect the insulin pump to a user’s body. The Company began commercial sales of its first product, t:slim, in August 2012 and subsequently commercialized t:flex in May 2015, t:slim G4 in September 2015 and t:slim X2 in October 2016. The t:slim X2 hardware platform now represents 100% of new pump shipments, but the Company continues to provide ongoing service and support to existing t:slim, t:slim G4 and t:flex customers. In August 2017, the Company received approval from the United States Food and Drug Administration (FDA) for the integration of t:slim X2 with the Dexcom G5 Mobile CGM system. In June 2018, the Company received FDA approval for t:slim X2 with Basal-IQ technology, the Company’s first-generation Automated Insulin Delivery (AID) algorithm, and the first insulin pump designated as compatible with integrated CGM (known as iCGM) devices. The Company commenced commercial sales of t:slim X2 with Basal-IQ technology integrated with the Dexcom G6 CGM in August 2018. During the third quarter of 2018, the Company commenced sales of the t:slim X2 with G5 integration through distribution partners in select European countries, in addition to Australia, New Zealand and South Africa. Direct sales efforts in Canada began in the fourth quarter of 2018 . During the second quarter of 2019, the Company began selling the t:slim X2 with Basal-IQ technology in select geographies outside of the United States. As of September 30, 2019 , the Company had $156.9 million in cash, cash equivalents and short-term investments. The Company has incurred operating losses since its inception and had an accumulated deficit of $627.5 million as of September 30, 2019 , which included a net loss of $27.4 million for the nine months ended September 30, 2019 . Management believes that the cash, cash equivalents and short-term investments on hand will be sufficient to satisfy the Company’s liquidity requirements for at least the next 12 months from the date of this filing. The Company’s ability to execute on its business strategy, meet its future liquidity requirements, and achieve and maintain profitable operations, is dependent on a number of factors, including its ability to continue to gain market acceptance of its products and achieve a level of revenues adequate to support its cost structure, achieve renewal pump sales objectives, develop and launch new products, expand the commercialization of products into new international markets, maximize manufacturing efficiencies, satisfy increasing production requirements, leverage the investments made in its sales, clinical, marketing and customer support organizations, and operate its business and manufacture and sell products without infringing on third party intellectual property rights. The Company has funded its operations primarily through private and public offerings of equity securities, and through debt financing which has since been fully repaid. The Company may in the future seek additional capital from public or private offerings of equity or debt securities, or it may elect to borrow capital under new credit arrangements or from other sources. If the Company issues equity or debt securities to raise additional funds, its existing stockholders may experience dilution, it may incur significant financing or debt service costs, and the new equity or debt securities may have rights, preferences and privileges senior to those of its existing stockholders. There can be no assurance that equity or debt financing will be available on acceptable terms, or at all. Basis of Presentation The Company has prepared the accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and pursuant to the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments which are of a normal and recurring nature, considered necessary for a fair presentation of the financial information contained herein, have been included. Interim financial results are not necessarily indicative of results anticipated for the full year or any other period(s). These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (Annual Report), from which the balance sheet information herein was derived. The condensed consolidated financial statements include the accounts of Tandem Diabetes Care, Inc. and its wholly owned subsidiary in Canada. All significant intercompany balances and transactions have been eliminated in consolidation.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies There have been no material changes to the Company's significant accounting policies during the nine months ended September 30, 2019 , as compared to those disclosed in the Annual Report other than adoption of the new lease accounting standard effective January 1, 2019 (See Note 6, “Leases”). Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes as of the date of the consolidated financial statements. Some of those judgments can be subjective and complex, and therefore, actual results could differ materially from those estimates under different assumptions or conditions. Segment Reporting Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker (CODM) in making decisions regarding resource allocation and assessing performance. The Company’s current product offering consists primarily of insulin pumps, disposable cartridges and infusion sets for the storage and delivery of insulin. The Company views its operations and manages its business as one segment as key operating decisions and resource allocations are made by the CODM using consolidated financial data. Accounts Receivable The Company grants credit to various customers in the ordinary course of business and is paid directly by customers who use the products, distributors and third-party insurance payors. The Company maintains an allowance for doubtful accounts for potential credit losses. Provisions are made based on historical experience, assessment of specific risk, review of outstanding invoices, and various assumptions and estimates that are believed to be reasonable under the circumstances. Uncollectible accounts are written off against the allowance after appropriate collection efforts have been exhausted and when it is deemed that a balance is uncollectible. Fair Value of Financial Instruments The Company believes the carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, accrued expenses, and employee-related liabilities are reasonable estimates of their fair values because of the short-term nature of these assets and liabilities. Short-term investments are carried at fair value. The Company believes the fair value of its operating lease liabilities at September 30, 2019 approximated their carrying value, based on the borrowing rates that were available for loans with similar terms as of that date. The estimated fair value of certain of the Company’s common stock warrants was determined using a Black-Scholes pricing model as of September 30, 2019 and December 31, 2018 (see Note 5, “Fair Value Measurements”). Revenue Recognition Revenue is generated primarily from sales of insulin pumps, disposable cartridges and infusion sets to individual customers and third-party distributors that resell the products to insulin-dependent diabetes customers. In January 2018, the Company adopted the Revenue from Contracts with Customers Standard which superseded existing revenue guidance under U.S. GAAP and International Financial Reporting Standards. Pursuant to the Revenue from Contracts with Customers Standard’s core principle, subsequent to January 1, 2018, the Company recognizes revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. The Company elected to implement this new standard utilizing the modified retrospective method. Under this approach, the Company applied the new standard to all new contracts initiated on or after the effective date, and for contracts which had remaining obligations as of the effective date the Company recorded an adjustment to the opening balance of accumulated deficit. The accounting for the significant majority of the Company’s revenues was not impacted by the new guidance. On January 1, 2018, the Company recorded a net reduction to accumulated deficit in the amount of $149,000 , to reflect the impact of the accounting change. Prior to the implementation of this new standard, revenue was recognized when persuasive evidence of an arrangement existed, delivery had occurred and title passed, the price was fixed or determinable, and collectability was reasonably assured. The Company considers the individual deliverables in its product offering as separate performance obligations. The transaction price is determined based on the consideration expected to be received, based either on the stated value in contractual arrangements or the estimated cash to be collected in non-contracted arrangements. The Company allocates the consideration to the individual performance obligations and recognizes the consideration based on when the performance obligation is satisfied, considering whether or not this occurs at a point in time or over time. Generally, insulin pumps, cartridges, infusion sets and accessories are deemed performance obligations that are satisfied at a point in time when the customer obtains control of the promised good, which is upon delivery, while access to the complementary products, such as the t:connect cloud-based data management application and the Tandem Device Updater, are considered performance obligations satisfied over the typical four-year warranty period of the insulin pumps. There is no standalone value for these complementary products. Therefore, the Company determines their value by applying the expected cost plus a margin approach and then allocates the residual to the insulin pumps. At September 30, 2019 and December 31, 2018 , $7.6 million and $3.8 million , respectively, were recorded as deferred revenue for these performance obligations that are satisfied over time. Additionally, the Company offers a 30 -day right of return to its customers from the date of shipment of any of its insulin pumps, provided a physician’s confirmation of the medical reason for the return is received. Estimated allowances for sales returns are based on historical returned quantities as compared to pump shipments in those same periods of return. The return rate is then applied to the sales of the current period to establish a reserve at the end of the period. The return rates used in the reserve are adjusted for known or expected changes in the marketplace when appropriate. The allowance for sales returns is recorded as a reduction of revenue and an increase in deferred revenue in the period in which the related sale is recorded. The amount recorded on the Company’s balance sheets for allowance for sales returns was $0.2 million and $0.3 million at September 30, 2019 and December 31, 2018 , respectively. Actual product returns have not differed materially from estimated amounts reserved in the accompanying condensed consolidated financial statements. Warranty Reserve The Company generally provides a four-year warranty on its insulin pumps to end user customers and may replace any pumps that do not function in accordance with the product specifications. Insulin pumps returned to the Company may be refurbished and redeployed. Additionally, the Company offers a six-month warranty on disposable cartridges and infusion sets. Estimated warranty costs are recorded at the time of shipment. Warranty costs are estimated based on the current expected product replacement cost and expected replacement rates based on historical experience. The Company evaluates the reserve quarterly and makes adjustments when appropriate. Changes to the actual replacement rates or the expected product replacement cost could have a material impact on the Company’s estimated warranty reserve. As of September 30, 2019 and December 31, 2018 , the warranty reserve was $16.1 million and $9.1 million , respectively. The following table provides a reconciliation of the change in product warranty liabilities from December 31, 2018 through September 30, 2019 (in thousands): Balance at December 31, 2018 $ 9,138 Provision for warranties issued during the period 13,790 Settlements made during the period (7,443 ) Increases in warranty estimates 607 Balance at September 30, 2019 $ 16,092 Current portion $ 5,963 Non-current portion 10,129 Total $ 16,092 Stock-Based Compensation Stock-based compensation cost is measured at the grant date based on the estimated fair value of the award, and the portion that is ultimately expected to vest is recognized as compensation expense over the requisite service period on a straight-line basis. The Company estimates the fair value of stock options issued under the Company’s Amended and Restated 2013 Stock Incentive Plan (2013 Plan), and the fair value of the employees’ purchase rights under the Company’s 2013 Employee Stock Purchase Plan (ESPP), using the Black-Scholes option-pricing model on the date of grant. The Black-Scholes option-pricing model requires the use of assumptions about a number of variables, including stock price volatility, expected term, dividend yield and risk-free interest rate. For awards that vest based on the achievement of service conditions, the Company recognizes expense using the straight-line method less estimated forfeitures based on historical experience. Net Loss Per Share Basic net loss per share is calculated by dividing the net loss by the weighted average number of shares of common stock that were outstanding for the period, without consideration of common stock equivalents. Diluted net loss per share is calculated in accordance with the treasury stock method and reflects the potential dilution that would occur if outstanding securities or other contracts to issue common stock were exercised or converted to common stock. Dilutive common stock equivalents are comprised of warrants, potential awards granted pursuant to the ESPP, and stock options outstanding under the Company’s equity incentive plans. For warrants that are recorded as a liability in the accompanying balance sheets, the calculation of diluted net loss per share requires that, to the extent the average market price of the underlying shares for the reporting period exceeds the exercise price of the warrants and the presumed exercise of the warrants is dilutive to loss per share for the period, an adjustment be made to net loss used in the calculation to remove the change in fair value of the warrants from the numerator for the period. Likewise, an adjustment to the denominator is required to reflect the related dilutive shares, if any, under the treasury stock method. For all periods presented other than the three months ended September 30, 2019, there is no difference in the number of shares used to calculate basic and diluted shares outstanding due to the Company’s net loss position. For the three months ended September 30, 2019, the net loss used in the calculation of diluted net loss per share was increased by $2.3 million to remove the decrease in fair value of common stock warrants based on the dilutive effect of assumed exercise, and the denominator was increased by 394,433 shares calculated under the treasury stock method. Potentially dilutive securities not included in the calculation of diluted net loss per share (because inclusion would be anti-dilutive) are as follows (in thousands, in common stock equivalent shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Warrants to purchase common stock 293 710 710 710 Options to purchase common stock 6,234 5,155 5,868 3,031 Awards granted under the ESPP 134 61 45 24 6,661 5,926 6,623 3,765 Recent Accounting Pronouncements 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, which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The new standard requires the use of forward-looking expected credit loss models based on historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount, which may result in earlier recognition of credit losses under the new standard. The new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income (loss) rather than reducing the carrying amount under the current, other-than-temporary-impairment model. The standard is effective for public business entities for annual periods beginning after December 15, 2019, and interim periods within those years. The Company plans to implement the new standard in the first quarter of 2020, and is in the process of reviewing its credit loss models to assess the impact of the adoption of the standard on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. The updated guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, with early adoption permitted. The Company is in the process of assessing the impact of the adoption of the updated guidance on its consolidated financial statements, as well as whether to early adopt the new standard. In August 2018, the FASB issued ASU No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which changes the accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. The updated guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The implementation costs should be presented as a prepaid asset on the balance sheets and expensed over the term of the hosting arrangement. The updated guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, with early adoption permitted. The Company is in the process of assessing the impact of the adoption of the updated guidance on its consolidated financial statements.

Short-Term Investments

Short-Term Investments	9 Months Ended
	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Short-Term Investments	Short-Term Investments The Company invests in marketable securities, principally debt instruments of the U.S. Government, and financial institutions and corporations with strong credit ratings. The following represents a summary of the estimated fair value of short-term investments as of September 30, 2019 and December 31, 2018 (in thousands): At September 30, 2019 Maturity (in years) Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Estimated Fair Value Available-for-sale securities: Commercial paper Less than 1 $ 24,997 $ 10 $ (3 ) $ 25,004 U.S. Government-sponsored enterprise Less than 2 21,830 9 (4 ) 21,835 U.S. Treasury securities Less than 1 12,710 18 — 12,728 Corporate debt securities Less than 2 51,242 83 (5 ) 51,320 Total $ 110,779 $ 120 $ (12 ) $ 110,887 At December 31, 2018 Maturity (in years) Amortized Cost Unrealized Gain Unrealized Loss Estimated Fair Value Available-for-sale securities: Commercial paper Less than 1 $ 53,559 $ — $ (22 ) $ 53,537 U.S. Treasury securities Less than 1 17,937 — (2 ) 17,935 Corporate debt securities Less than 1 15,718 12 (1 ) 15,729 Total $ 87,214 $ 12 $ (25 ) $ 87,201 The Company has classified all marketable securities, regardless of maturity, as short-term investments based upon the Company's ability and intent to use any and all of those marketable securities to satisfy the Company's current liquidity requirements. The Company periodically reviews the portfolio of available-for-sale debt securities to determine if any investment is other-than-temporarily impaired due to changes in credit risk or other potential valuation concerns. The Company believes that the short-term investments held at September 30, 2019 were not other-than-temporarily impaired. Unrealized losses on available-for-sale debt securities at that date were not significant and were due to changes in interest rates, including credit spreads, and not due to increased credit risks associated with specific securities. The Company does not intend to sell the available-for-sale debt securities that are in an unrealized loss position, and it is not more likely than not that the Company will be required to sell these debt securities before recovery of their amortized cost bases, which may be at maturity.

Inventories

Inventories	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consisted of the following as of September 30, 2019 and December 31, 2018 (in thousands): September 30, December 31, Raw materials $ 12,488 $ 6,622 Work-in-process 11,051 2,710 Finished goods 17,192 10,564 Total $ 40,732 $ 19,896

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Authoritative guidance on fair value measurements defines fair value and provides a consistent framework for both measuring fair value as well as for disclosures of each major asset and liability category measured at fair value on either a recurring or a nonrecurring basis. Fair value is intended to reflect an assumed exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the authoritative guidance provides a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities. Level 2: Inputs, other than quoted prices in active markets, that are observable either directly or indirectly for substantially the full term of the asset or liability. Level 3: Unobservable inputs in which there is little or no market data and that are significant to the fair value of the assets or liabilities, which require the reporting entity to develop its own valuation techniques that require input assumptions. The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2019 and December 31, 2018 , and indicates the fair value hierarchy of the valuation techniques utilized by the Company to determine such fair value (in thousands): Fair Value Measurements at (Level 1) (Level 2) (Level 3) Assets Cash equivalents (1) $ 37,987 $ 37,987 $ — $ — Commercial paper 25,004 — 25,004 — U.S. Government-sponsored enterprise 21,835 — 21,835 — U.S. Treasury securities 12,728 12,728 — — Corporate debt securities 51,320 — 51,320 — Total assets $ 148,874 $ 50,715 $ 98,159 $ — Liabilities Common stock warrants $ 23,283 $ — $ — $ 23,283 Total liabilities $ 23,283 $ — $ — $ 23,283 Fair Value Measurements at (Level 1) (Level 2) (Level 3) Assets Cash equivalents (1) $ 37,373 $ 37,373 $ — $ — Commercial paper 53,537 — 53,537 — U.S. Treasury securities 17,935 17,935 — — Corporate debt securities 15,729 — 15,729 — Total assets $ 124,574 $ 55,308 $ 69,266 $ — Liabilities Common stock warrants $ 17,926 $ — $ — $ 17,926 Total liabilities $ 17,926 $ — $ — $ 17,926 (1) Generally, cash equivalents include money market funds and investments with a maturity of three months or less from the date of purchase. The Company’s Level 2 financial instruments are valued using market prices on less active markets with observable valuation inputs such as interest rates and yield curves. The Company obtains the fair value of Level 2 financial instruments from quoted market prices, calculated prices or quotes from third-party pricing services. The Company validates these prices through independent valuation testing and review of portfolio valuations provided by the Company’s investment managers. There were no transfers between Level 1 and Level 2 assets during the nine months ended September 30, 2019 and 2018. The Company’s Level 3 liabilities at September 30, 2019 and December 31, 2018 include the Series A warrants issued by the Company in connection with the public offering of common stock in October 2017. The Series A warrants have a term of five years and initially provided holders the right to purchase 4,630,000 shares of the Company’s common stock at an exercise price of $3.50 per share. The Series A warrants were initially valued in the aggregate amount of $5.2 million on the date of issuance utilizing a Black-Scholes pricing model. The Company reassesses the fair value of the outstanding Series A warrants at each reporting date utilizing a Black-Scholes pricing model. Variables used in the pricing model include the market price of the Company’s common stock and estimates of stock price volatility, dividend yield, expected warrant term and risk-free interest rate. The Company develops its estimates based on publicly available historical data. The assumptions used to estimate the fair values of the outstanding Series A warrants at September 30, 2019 and December 31, 2018 are presented below: September 30, 2019 December 31, 2018 Risk-free interest rate 1.6 % 3.0 % Expected dividend yield 0.0 % 0.0 % Expected volatility 83.3 % 78.3 % Expected term (in years) 3.0 3.8 The following table presents a summary of changes in the fair value of the Company’s Level 3 financial liabilities for the nine months ended September 30, 2019 and 2018 : Nine Months Ended September 30, 2019 2018 Balance at beginning of period $ 17,926 $ 5,432 Increase in fair value included in change in fair value of common stock warrants 10,849 69,042 Decrease in fair value from warrants exercised during the period (5,492 ) (53,831 ) Balance at end of period $ 23,283 $ 20,643 During the nine months ended September 30, 2019 , the Company issued 93,470 shares of common stock upon the exercise of Series A warrants. During the nine months ended September 30, 2018 , the Company issued 8,598,076 shares of common stock upon the exercise of certain warrants issued in October 2017, and 13,450 warrants expired unexercised. As of September 30, 2019 , there were Series A warrants outstanding to purchase 417,315 shares of the Company's common stock (see Note 8, “Stockholders’ Equity”).

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard and its related amendments (collectively referred to as ASC 842) requires lessees to recognize right-of-use assets and corresponding lease liabilities for all leases with lease terms of greater than 12 months. It also changed the definition of a lease and expanded the disclosure requirements of lease arrangements. In July 2018, the FASB added a transition option for implementation of the standard that allowed companies to continue to use the legacy guidance in ASC 840, Leases , including its disclosure requirements, in the comparative periods presented in the year of adoption. The new standard must be adopted using the modified retrospective approach and was effective for the Company starting in the first quarter of fiscal 2019. The Company elected the transition option and certain practical expedients, and recognized a cumulative-effect transition adjustment for the recognition of right-of-use leased assets and corresponding operating lease liabilities of $12.4 million on the consolidated balance sheets upon adoption of the standard as of January 1, 2019. The Company did not restate prior periods. Deferred rent of $1.0 million and $3.8 million as of January 1, 2019 was reclassified from other current liabilities and deferred rent long-term, respectively, to a reduction of the right-of-use leased assets in connection with the adoption of the standard. The Company's leases consist primarily of operating leases for general office space, laboratory, manufacturing, and warehouse facilities, and equipment. Leases with an initial term of 12 months or less are not recorded on the balance sheets. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. Because the Company's leases do not provide an implicit interest rate, the Company uses its incremental borrowing rate based on the information available at the lease commencement date in determining the present value of future lease payments. The Company used the incremental borrowing rate on January 1, 2019 for operating leases that commenced prior to that date. For lease agreements entered into or reassessed after the adoption of ASC 842, the Company combines lease and non-lease components. Certain leases include an option to renew, with renewal terms that can extend the lease term for additional periods. The exercise of lease renewal options is at the Company's sole discretion. The depreciable life of assets and leasehold improvements are limited by the expected lease term, unless there is a transfer of title or purchase option that is reasonably certain to be exercised. In January 2019, the Company entered into a lease agreement for approximately 25,332 square feet of additional general administrative office space (Initial Premises) located at 10935 Vista Sorrento Parkway, San Diego, California (Vista Sorrento Parkway Lease). The lease term for the Initial Premises commenced in March 2019 and expires in September 2022. In May 2019, the Company entered into a First Amendment to the Vista Sorrento Parkway Lease (First Amendment) to expand the leased premises by adding approximately 33,681 square feet of additional general administrative office space (Expansion Space), and to extend the lease term for the Initial Premises through December 2022. The lease term for the Expansion Space commenced in May 2019 and expires in December 2022. The Company has a one-time option to extend the term of the Vista Sorrento Parkway Lease, covering both the Initial Premises and the Expansion Space, for a period of four years . The Company recognized right-of-use leased assets and corresponding operating lease liabilities of $3.1 million on the consolidated balance sheets in the first quarter of 2019 related to the Initial Premises, and $4.5 million in the second quarter of 2019 related to the First Amendment to the Vista Sorrento Parkway Lease. In March 2019, the Company entered into a lease agreement for approximately 40,490 square feet of space located at 6495 Marindustry Place, San Diego, California to house additional operations functions, including warehousing and shipping (Marindustry Place Lease). The lease term commenced in May 2019 and expires in April 2026. The Company has a one-time option to extend the term of the Marindustry Place Lease for a period of no less than three years and no more than five years . The Company recognized right-of-use leased assets and corresponding operating lease liabilities of $3.4 million on the consolidated balance sheets in the second quarter of 2019 related to the Marindustry Place Lease. Future minimum lease payments under non-cancellable operating leases as of September 30, 2019 were as follows (in thousands): Years Ending December 31, 2019 (remaining) $ 867 2020 6,831 2021 7,100 2022 5,880 2023 1,991 Thereafter 1,577 Total future minimum lease payments 24,246 Less: amount representing interest (3,037 ) Present value of future minimum lease payments 21,209 Less: current portion of operating lease liabilities (5,951 ) Operating lease liabilities - long-term $ 15,258

Term Loan Agreement

Term Loan Agreement	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Term Loan Agreement	Term Loan Agreement In August 2018, the Company fully repaid the term loan made by Capital Royalty Partners II, L.P. and its affiliated funds (CRG) pursuant to the Amended and Restated Term Loan Agreement (Term Loan Agreement). The balance of the outstanding debt during 2018 up until the time of repayment was $82.7 million . The repayment included approximately $1.1 million in accrued interest and approximately $5.0 million in associated financing fees that became due. As a result of the repayment, the Company did not have any borrowings outstanding under the Term Loan Agreement as of September 30, 2019 or December 31, 2018 . Under the Term Loan Agreement, interest was payable at the Company’s option, (i) in cash at a rate of 11.5% per annum, or (ii) at a rate of 9.5% of the 11.5% per annum in cash and 2.0% of the 11.5% per annum (PIK Loan) to be added to the principal of the loan and subject to accruing interest. The Company entered into a series of amendments to the Term Loan Agreement between 2016 and 2018 , which included the addition of a financing fee payable at the maturity of the Company’s loans, the issuance of 193,788 ten -year warrants to CRG to purchase shares of the Company’s common stock at an exercise price of $23.50 per share and certain other minimum financing covenants. The financing fee was applicable to the entire aggregate principal amount of borrowings outstanding, including total PIK Loans issued. As of September 30, 2019 , the warrants to purchase 193,788 shares of the Company's common stock at an exercise price of $23.50 per share remained outstanding.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Public Offerings In the first quarter of 2018 , the Company completed a public offering of 34,500,000 shares of common stock at a public offering price of $2.00 per share. The gross proceeds to the Company from the offering were approximately $69.0 million , before deducting underwriting discounts and commissions and other offering expenses payable by the Company. In the third quarter of 2018, the Company completed a public offering of 4,035,085 shares of common stock at a public offering price of $28.50 per share. The gross proceeds to the Company from the offering were $115.0 million , before deducting underwriting discounts and commissions and other offering expenses payable by the Company. Shares Reserved for Future Issuance The following shares of the Company’s common stock were reserved for future issuance as of September 30, 2019 (in thousands): Shares underlying outstanding warrants 710 Shares underlying outstanding stock options 7,358 Shares authorized for future equity award grants 3,165 Shares authorized for issuance pursuant to awards granted under the ESPP 1,852 13,085 As of September 30, 2019 , there were Series A warrants outstanding to purchase 417,315 shares of the Company's common stock at an exercise price of $3.50 per share, which were issued in connection with the October 2017 Financing, and which expire in October 2022. Also outstanding as of September 30, 2019, were warrants to purchase 193,788 shares of the Company's common stock at an exercise price of $23.50 per share, which were issued in March 2017, and which expire in March 2027 (see Note 7, “Term Loan Agreement”), and warrants to purchase 98,965 shares of the Company's common stock at an exercise price of $73.73 per share, which were issued between August 2011 and August 2012, and which expire between August 2021 and August 2022. The Company issued 200 and 93,470 shares of its common stock upon the exercise of warrants during the three and nine months ended September 30, 2019 , respectively. The Company issued 8,603,321 shares of its common stock upon the exercise of warrants during the year ended December 31, 2018 . In both June 2019 and 2018, the Company received approval from its stockholders to increase the number of shares of its common stock reserved for issuance under the 2013 Plan by 5,000,000 and 5,500,000 shares, respectively. The Company issued 439,646 and 1,213,428 shares of its common stock upon the exercise of stock options during the three and nine months ended September 30, 2019 , respectively. The Company issued 136,042 shares of its common stock upon the exercise of stock options during the year ended December 31, 2018 . The ESPP enables eligible employees to purchase shares of the Company's common stock using their after-tax payroll deductions, subject to certain conditions. Historically, offerings under the ESPP consisted of a two-year offering period with four six-month purchase periods which begin in May and November of each year. The Company previously suspended the ESPP in May 2017 due to a lack of available shares. In June 2018, the Company received approval from its stockholders to increase the number of shares of its common stock reserved for issuance under the ESPP by 2,000,000 shares. A new offering commenced under the ESPP on June 15, 2018, and the first purchase date was November 15, 2018. There were 168,165 shares of common stock purchased under the ESPP in the nine months ended September 30, 2019 . There were 80,581 shares of common stock purchased under the ESPP during the year ended December 31, 2018 . Stock-Based Compensation In June 2019, the Company granted options to purchase 1,644,715 shares of common stock under the 2013 Plan, which were originally awarded between February 2019 and June 2019, subject to and conditioned upon the approval by its stockholders of an increase in the number of shares of common stock reserved for issuance under the 2013 Plan. In total, the Company granted options to purchase 2,916,906 shares of common stock under the 2013 Plan during the nine months ended September 30, 2019 . These options have an exercise price equal to the closing price of the Company's common stock on the applicable award date, and generally vest as to 25% of the underlying shares on the first anniversary of the award, with the balance of the options vesting monthly over the following three years. In June 2018, the Company granted options to purchase 811,800 shares of common stock under the 2013 Plan, which were originally awarded on December 1, 2017, subject to and conditioned upon the approval by its stockholders of an increase in the number of shares of common stock authorized under the 2013 Plan. These options have an exercise price equal to the closing price of the Company's common stock on the applicable award date, and generally vest as to 50% of the underlying shares on the first anniversary of the award, with the balance of the options vesting monthly over the following year. The Company also granted options to purchase 3,661,220 shares of common stock under the 2013 Plan during the nine months ended September 30, 2018. These options have an exercise price equal to the closing price of the Company's common stock on the applicable award date, and generally vest as to 25% of the underlying shares on the first anniversary of the award, with the balance of the options vesting monthly over the following three years, except with respect to options to purchase 3,389,300 shares of common stock granted in June 2018, which vest as to 50% of the underlying shares on the first anniversary of the award, with the balance of the options vesting monthly over the following year. The assumptions used in the Black-Scholes option-pricing model are as follows: Stock Options Three Months Ended Nine Months Ended 2019 2018 2019 2018 Weighted average grant date fair value (per share) $ 38.74 $ 21.77 $ 39.08 $ 12.35 Risk-free interest rate 1.7 % 2.8 % 2.1 % 2.8 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Expected volatility 71.8 % 70.5 % 71.8 % 71.4 % Expected term (in years) 6.1 6.1 6.0 5.7 ESPP Nine Months Ended 2019 2018 Weighted average grant date fair value (per share) $ 33.49 $ 9.62 Risk-free interest rate 2.3 % 2.4 % Expected dividend yield 0.0 % 0.0 % Expected volatility 75.9 % 77.0 % Expected term (in years) 1.3 1.3 The Company records stock-based compensation expense associated with the ESPP using the Black-Scholes option-pricing model. Valuations are performed on the grant date at the beginning of the purchase period, which generally occurs in May and November of each year. The following table summarizes the allocation of stock-based compensation expense included in the consolidated statement of operations (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Cost of sales $ 1,751 $ 784 $ 4,178 $ 1,129 Selling, general & administrative 13,110 6,821 29,060 9,833 Research and development 2,369 1,932 6,148 2,465 Total $ 17,230 $ 9,537 $ 39,386 $ 13,427 The total stock-based compensation expense capitalized as part of the cost of the Company’s inventories was $0.8 million and $0.4 million as of September 30, 2019 and December 31, 2018 , respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies From time to time, the Company may be subject to legal proceedings or regulatory matters arising in the ordinary course of business, including actions with respect to intellectual property, employment, regulatory, product liability and contractual matters. In connection with these proceedings or matters, the Company regularly assesses the probability and amount (or range) of possible issues based on the developments in these proceedings or matters. A liability is recorded in the consolidated financial statements if it is determined that it is probable that a loss has been incurred, and that the amount (or range) of the loss can be reasonably estimated. Because of the uncertainties related to any pending proceedings or matters, the Company is currently unable to predict their ultimate outcome and, with respect to any legal proceeding or regulatory matter where no liability has been accrued, to make a reasonable estimate of the possible loss (or range of loss) that could result from an adverse outcome. As of September 30, 2019 and December 31, 2018 , there were no legal proceedings, regulatory matters, or other disputes or claims for which a material loss was considered probable or for which the amount (or range) of loss was reasonably estimable. However, regardless of the outcome, legal proceedings, regulatory matters, and other disputes and claims can have an adverse impact on the Company because of legal costs, diversion of management time and resources, and other factors.

Organization and Basis of Pre_2

Organization and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The Company has prepared the accompanying unaudited condensed consolidated financial statements in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and pursuant to the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. In the opinion of management, all adjustments which are of a normal and recurring nature, considered necessary for a fair presentation of the financial information contained herein, have been included. Interim financial results are not necessarily indicative of results anticipated for the full year or any other period(s). These unaudited condensed consolidated financial statements should be read in conjunction with the Company’s audited consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (Annual Report), from which the balance sheet information herein was derived. The condensed consolidated financial statements include the accounts of Tandem Diabetes Care, Inc. and its wholly owned subsidiary in Canada. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes as of the date of the consolidated financial statements. Some of those judgments can be subjective and complex, and therefore, actual results could differ materially from those estimates under different assumptions or conditions.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which discrete financial information is available for evaluation by the chief operating decision-maker (CODM) in making decisions regarding resource allocation and assessing performance. The Company’s current product offering consists primarily of insulin pumps, disposable cartridges and infusion sets for the storage and delivery of insulin. The Company views its operations and manages its business as one segment as key operating decisions and resource allocations are made by the CODM using consolidated financial data.
Accounts Receivable	Accounts Receivable The Company grants credit to various customers in the ordinary course of business and is paid directly by customers who use the products, distributors and third-party insurance payors. The Company maintains an allowance for doubtful accounts for potential credit losses. Provisions are made based on historical experience, assessment of specific risk, review of outstanding invoices, and various assumptions and estimates that are believed to be reasonable under the circumstances. Uncollectible accounts are written off against the allowance after appropriate collection efforts have been exhausted and when it is deemed that a balance is uncollectible.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company believes the carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, accrued expenses, and employee-related liabilities are reasonable estimates of their fair values because of the short-term nature of these assets and liabilities. Short-term investments are carried at fair value. The Company believes the fair value of its operating lease liabilities at September 30, 2019 approximated their carrying value, based on the borrowing rates that were available for loans with similar terms as of that date. The estimated fair value of certain of the Company’s common stock warrants was determined using a Black-Scholes pricing model as of September 30, 2019 and December 31, 2018 (see Note 5, “Fair Value Measurements”).
Revenue Recognition	Revenue Recognition Revenue is generated primarily from sales of insulin pumps, disposable cartridges and infusion sets to individual customers and third-party distributors that resell the products to insulin-dependent diabetes customers. In January 2018, the Company adopted the Revenue from Contracts with Customers Standard which superseded existing revenue guidance under U.S. GAAP and International Financial Reporting Standards. Pursuant to the Revenue from Contracts with Customers Standard’s core principle, subsequent to January 1, 2018, the Company recognizes revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those goods or services. The Company elected to implement this new standard utilizing the modified retrospective method. Under this approach, the Company applied the new standard to all new contracts initiated on or after the effective date, and for contracts which had remaining obligations as of the effective date the Company recorded an adjustment to the opening balance of accumulated deficit. The accounting for the significant majority of the Company’s revenues was not impacted by the new guidance. On January 1, 2018, the Company recorded a net reduction to accumulated deficit in the amount of $149,000 , to reflect the impact of the accounting change. Prior to the implementation of this new standard, revenue was recognized when persuasive evidence of an arrangement existed, delivery had occurred and title passed, the price was fixed or determinable, and collectability was reasonably assured. The Company considers the individual deliverables in its product offering as separate performance obligations. The transaction price is determined based on the consideration expected to be received, based either on the stated value in contractual arrangements or the estimated cash to be collected in non-contracted arrangements. The Company allocates the consideration to the individual performance obligations and recognizes the consideration based on when the performance obligation is satisfied, considering whether or not this occurs at a point in time or over time. Generally, insulin pumps, cartridges, infusion sets and accessories are deemed performance obligations that are satisfied at a point in time when the customer obtains control of the promised good, which is upon delivery, while access to the complementary products, such as the t:connect cloud-based data management application and the Tandem Device Updater, are considered performance obligations satisfied over the typical four-year warranty period of the insulin pumps. There is no standalone value for these complementary products. Therefore, the Company determines their value by applying the expected cost plus a margin approach and then allocates the residual to the insulin pumps. At September 30, 2019 and December 31, 2018 , $7.6 million and $3.8 million , respectively, were recorded as deferred revenue for these performance obligations that are satisfied over time. Additionally, the Company offers a 30 -day right of return to its customers from the date of shipment of any of its insulin pumps, provided a physician’s confirmation of the medical reason for the return is received. Estimated allowances for sales returns are based on historical returned quantities as compared to pump shipments in those same periods of return. The return rate is then applied to the sales of the current period to establish a reserve at the end of the period. The return rates used in the reserve are adjusted for known or expected changes in the marketplace when appropriate. The allowance for sales returns is recorded as a reduction of revenue and an increase in deferred revenue in the period in which the related sale
Warranty Reserve	Warranty Reserve
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation cost is measured at the grant date based on the estimated fair value of the award, and the portion that is ultimately expected to vest is recognized as compensation expense over the requisite service period on a straight-line basis. The Company estimates the fair value of stock options issued under the Company’s Amended and Restated 2013 Stock Incentive Plan (2013 Plan), and the fair value of the employees’ purchase rights under the Company’s 2013 Employee Stock Purchase Plan (ESPP), using the Black-Scholes option-pricing model on the date of grant. The Black-Scholes option-pricing model requires the use of assumptions about a number of variables, including stock price volatility, expected term, dividend yield and risk-free interest rate. For awards that vest based on the achievement of service conditions, the Company recognizes expense using the straight-line method less estimated forfeitures based on historical experience.
Net Loss Per Share	Net Loss Per Share
Recent Accounting Pronouncements	Recent Accounting Pronouncements 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, which modifies the measurement and recognition of credit losses for most financial assets and certain other instruments. The new standard requires the use of forward-looking expected credit loss models based on historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount, which may result in earlier recognition of credit losses under the new standard. The new standard also requires that credit losses related to available-for-sale debt securities be recorded as an allowance through net income (loss) rather than reducing the carrying amount under the current, other-than-temporary-impairment model. The standard is effective for public business entities for annual periods beginning after December 15, 2019, and interim periods within those years. The Company plans to implement the new standard in the first quarter of 2020, and is in the process of reviewing its credit loss models to assess the impact of the adoption of the standard on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement , which adds and modifies certain disclosure requirements for fair value measurements. Under the new guidance, entities will no longer be required to disclose the amount of and reasons for transfers between Level 1 and Level 2 of the fair value hierarchy, or valuation processes for Level 3 fair value measurements. However, public companies will be required to disclose the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and related changes in unrealized gains and losses included in other comprehensive income. The updated guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, with early adoption permitted. The Company is in the process of assessing the impact of the adoption of the updated guidance on its consolidated financial statements, as well as whether to early adopt the new standard. In August 2018, the FASB issued ASU No. 2018-15, Customer's Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract , which changes the accounting for implementation costs incurred in a cloud computing arrangement that is a service contract. The updated guidance aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software. The implementation costs should be presented as a prepaid asset on the balance sheets and expensed over the term of the hosting arrangement. The updated guidance is effective for annual periods beginning after December 15, 2019, and interim periods within those periods, with early adoption permitted. The Company is in the process of assessing the impact of the adoption of the updated guidance on its consolidated financial statements.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Reconciliation of Change in Product Warranty Liabilities	The following table provides a reconciliation of the change in product warranty liabilities from December 31, 2018 through September 30, 2019 (in thousands): Balance at December 31, 2018 $ 9,138 Provision for warranties issued during the period 13,790 Settlements made during the period (7,443 ) Increases in warranty estimates 607 Balance at September 30, 2019 $ 16,092 Current portion $ 5,963 Non-current portion 10,129 Total $ 16,092
Schedule of Anti-Dilutive Securities	Potentially dilutive securities not included in the calculation of diluted net loss per share (because inclusion would be anti-dilutive) are as follows (in thousands, in common stock equivalent shares): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Warrants to purchase common stock 293 710 710 710 Options to purchase common stock 6,234 5,155 5,868 3,031 Awards granted under the ESPP 134 61 45 24 6,661 5,926 6,623 3,765

Short-Term Investments (Tables)

Short-Term Investments (Tables)	9 Months Ended
	Sep. 30, 2019
Investments, Debt and Equity Securities [Abstract]
Summary of Estimated Fair Value of Short-Term Investments	The following represents a summary of the estimated fair value of short-term investments as of September 30, 2019 and December 31, 2018 (in thousands): At September 30, 2019 Maturity (in years) Amortized Cost Gross Unrealized Gain Gross Unrealized Loss Estimated Fair Value Available-for-sale securities: Commercial paper Less than 1 $ 24,997 $ 10 $ (3 ) $ 25,004 U.S. Government-sponsored enterprise Less than 2 21,830 9 (4 ) 21,835 U.S. Treasury securities Less than 1 12,710 18 — 12,728 Corporate debt securities Less than 2 51,242 83 (5 ) 51,320 Total $ 110,779 $ 120 $ (12 ) $ 110,887 At December 31, 2018 Maturity (in years) Amortized Cost Unrealized Gain Unrealized Loss Estimated Fair Value Available-for-sale securities: Commercial paper Less than 1 $ 53,559 $ — $ (22 ) $ 53,537 U.S. Treasury securities Less than 1 17,937 — (2 ) 17,935 Corporate debt securities Less than 1 15,718 12 (1 ) 15,729 Total $ 87,214 $ 12 $ (25 ) $ 87,201

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Summary of Inventories	Inventories consisted of the following as of September 30, 2019 and December 31, 2018 (in thousands): September 30, December 31, Raw materials $ 12,488 $ 6,622 Work-in-process 11,051 2,710 Finished goods 17,192 10,564 Total $ 40,732 $ 19,896

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of September 30, 2019 and December 31, 2018 , and indicates the fair value hierarchy of the valuation techniques utilized by the Company to determine such fair value (in thousands): Fair Value Measurements at (Level 1) (Level 2) (Level 3) Assets Cash equivalents (1) $ 37,987 $ 37,987 $ — $ — Commercial paper 25,004 — 25,004 — U.S. Government-sponsored enterprise 21,835 — 21,835 — U.S. Treasury securities 12,728 12,728 — — Corporate debt securities 51,320 — 51,320 — Total assets $ 148,874 $ 50,715 $ 98,159 $ — Liabilities Common stock warrants $ 23,283 $ — $ — $ 23,283 Total liabilities $ 23,283 $ — $ — $ 23,283 Fair Value Measurements at (Level 1) (Level 2) (Level 3) Assets Cash equivalents (1) $ 37,373 $ 37,373 $ — $ — Commercial paper 53,537 — 53,537 — U.S. Treasury securities 17,935 17,935 — — Corporate debt securities 15,729 — 15,729 — Total assets $ 124,574 $ 55,308 $ 69,266 $ — Liabilities Common stock warrants $ 17,926 $ — $ — $ 17,926 Total liabilities $ 17,926 $ — $ — $ 17,926 (1) Generally, cash equivalents include money market funds and investments with a maturity of three months or less from the date of purchase.
Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants	The assumptions used to estimate the fair values of the outstanding Series A warrants at September 30, 2019 and December 31, 2018 are presented below: September 30, 2019 December 31, 2018 Risk-free interest rate 1.6 % 3.0 % Expected dividend yield 0.0 % 0.0 % Expected volatility 83.3 % 78.3 % Expected term (in years) 3.0 3.8
Summary of Changes in Fair Value of Total Level 3 Financial Assets	The following table presents a summary of changes in the fair value of the Company’s Level 3 financial liabilities for the nine months ended September 30, 2019 and 2018 : Nine Months Ended September 30, 2019 2018 Balance at beginning of period $ 17,926 $ 5,432 Increase in fair value included in change in fair value of common stock warrants 10,849 69,042 Decrease in fair value from warrants exercised during the period (5,492 ) (53,831 ) Balance at end of period $ 23,283 $ 20,643

Leases Leases (Tables)

Leases Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Schedule of Future Minimum Payments Under Non-cancellable Operating Leases	Future minimum lease payments under non-cancellable operating leases as of September 30, 2019 were as follows (in thousands): Years Ending December 31, 2019 (remaining) $ 867 2020 6,831 2021 7,100 2022 5,880 2023 1,991 Thereafter 1,577 Total future minimum lease payments 24,246 Less: amount representing interest (3,037 ) Present value of future minimum lease payments 21,209 Less: current portion of operating lease liabilities (5,951 ) Operating lease liabilities - long-term $ 15,258

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Schedule of Shares of Common Stock Reserved for Future Issuance	The following shares of the Company’s common stock were reserved for future issuance as of September 30, 2019 (in thousands): Shares underlying outstanding warrants 710 Shares underlying outstanding stock options 7,358 Shares authorized for future equity award grants 3,165 Shares authorized for issuance pursuant to awards granted under the ESPP 1,852 13,085
Schedule of Assumptions Used in Black-Scholes Option-Pricing Model	The assumptions used in the Black-Scholes option-pricing model are as follows: Stock Options Three Months Ended Nine Months Ended 2019 2018 2019 2018 Weighted average grant date fair value (per share) $ 38.74 $ 21.77 $ 39.08 $ 12.35 Risk-free interest rate 1.7 % 2.8 % 2.1 % 2.8 % Expected dividend yield 0.0 % 0.0 % 0.0 % 0.0 % Expected volatility 71.8 % 70.5 % 71.8 % 71.4 % Expected term (in years) 6.1 6.1 6.0 5.7 ESPP Nine Months Ended 2019 2018 Weighted average grant date fair value (per share) $ 33.49 $ 9.62 Risk-free interest rate 2.3 % 2.4 % Expected dividend yield 0.0 % 0.0 % Expected volatility 75.9 % 77.0 % Expected term (in years) 1.3 1.3
Summary for Allocation of Stock-Based Compensation Expense	The following table summarizes the allocation of stock-based compensation expense included in the consolidated statement of operations (in thousands): Three Months Ended Nine Months Ended 2019 2018 2019 2018 Cost of sales $ 1,751 $ 784 $ 4,178 $ 1,129 Selling, general & administrative 13,110 6,821 29,060 9,833 Research and development 2,369 1,932 6,148 2,465 Total $ 17,230 $ 9,537 $ 39,386 $ 13,427

Organization and Basis of Pre_3

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Organization And Basis Of Presentation [Line Items]
Cash and cash equivalents and short-term investments	$ 156,900		$ 156,900
Accumulated deficit	(627,480)		(627,480)		$ (600,075)
Net loss	$ (2,901)	$ (34,245)	$ (27,405)	$ (126,299)
Insulin Pump | Minimum
Organization And Basis Of Presentation [Line Items]
Expected life span term			4 years
T:slim X2
Organization And Basis Of Presentation [Line Items]
Percentage of new pump shipments represented by product hardware platform			100.00%

Summary of Significant Accoun_3

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)shares	Sep. 30, 2019USD ($)segment	Dec. 31, 2018USD ($)	Jan. 01, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | segment		1
Deferred revenue	$ 8,187	$ 8,187
Offered period for sales return		30 days
Allowance for product returns	200	$ 200	$ 300
Warranty reserve	16,092	16,092	9,138
Increase in loss used for dilutive calculation	$ 2,300
Increase in denominator shares (in shares) | shares	394,433
Warranty reserves
Summary Of Significant Accounting Policies [Line Items]
Warranty reserve	$ 16,092	$ 16,092	9,100
Complementary products
Summary Of Significant Accounting Policies [Line Items]
Revenue performance obligations satisfied over period	4 years	4 years
Deferred revenue	$ 7,600	$ 7,600	$ 3,800
Tandem Pump
Summary Of Significant Accounting Policies [Line Items]
Warranty period offered		4 years
Slim cartridges and infusion sets
Summary Of Significant Accounting Policies [Line Items]
Warranty period offered		6 months
ASU 2014-09: Revenue from Contracts with Customers [Member]
Summary Of Significant Accounting Policies [Line Items]
Net reduction to accumulated deficit				$ 149

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Summary of Reconciliation of Change in Product Warranty Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Movement in Standard and Extended Product Warranty Accrual, Increase (Decrease) [Roll Forward]
Beginning balance	$ 9,138
Provision for warranties issued during the period	13,790
Settlements made during the period	(7,443)
Increases in warranty estimates	607
Ending balance	16,092
Current portion		$ 5,963
Non-current portion		10,129
Total	$ 9,138	$ 16,092

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Anti-Dilutive Securities (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	6,661	5,926	6,623	3,765
ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	134	61	45	24
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	293	710	710	710
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	6,234	5,155	5,868	3,031

Short-Term Investments - Summar

Short-Term Investments - Summary of Estimated Fair Value of Short-Term Investments (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Cash Cash Equivalents And Short Term Investments [Line Items]
Short-term investments, Amortized Cost	$ 110,779	$ 87,214
Short-term investments, Unrealized Gain	120	12
Short-term investments, Unrealized Loss	(12)	(25)
Short-term investments, Estimated Fair Value	110,887	87,201
Commercial paper
Cash Cash Equivalents And Short Term Investments [Line Items]
Amortized Cost	24,997	53,559
Gross Unrealized Gain	10	0
Gross Unrealized Loss	(3)	(22)
Estimated Fair Value	$ 25,004	$ 53,537
Commercial paper | Maximum
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale securities, Maturity (in years)	1 year	1 year
U.S. Government-sponsored enterprise
Cash Cash Equivalents And Short Term Investments [Line Items]
Amortized Cost	$ 21,830
Gross Unrealized Gain	9
Gross Unrealized Loss	(4)
Estimated Fair Value	$ 21,835
U.S. Government-sponsored enterprise | Maximum
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale securities, Maturity (in years)	2 years
U.S. Treasury securities
Cash Cash Equivalents And Short Term Investments [Line Items]
Amortized Cost	$ 12,710	$ 17,937
Gross Unrealized Gain	18	0
Gross Unrealized Loss	0	(2)
Estimated Fair Value	$ 12,728	$ 17,935
U.S. Treasury securities | Maximum
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale securities, Maturity (in years)	1 year	1 year
Corporate debt securities
Cash Cash Equivalents And Short Term Investments [Line Items]
Amortized Cost	$ 51,242	$ 15,718
Gross Unrealized Gain	83	12
Gross Unrealized Loss	(5)	(1)
Estimated Fair Value	$ 51,320	$ 15,729
Corporate debt securities | Maximum
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale securities, Maturity (in years)	2 years	1 year

Inventories - Summary of Invent

Inventories - Summary of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 12,488	$ 6,622
Work-in-process	11,051	2,710
Finished goods	17,192	10,564
Total	$ 40,732	$ 19,896

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 148,874	$ 124,574
Total liabilities	23,283	17,926
Common stock warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities	23,283	17,926
(Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	50,715	55,308
Total liabilities	0	0
(Level 1) | Common stock warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities	0	0
(Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	98,159	69,266
Total liabilities	0	0
(Level 2) | Common stock warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities	0	0
(Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Total liabilities	23,283	17,926
(Level 3) | Common stock warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total liabilities	23,283	17,926
Cash equivalents
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	37,987	37,373
Cash equivalents | (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	37,987	37,373
Cash equivalents | (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Cash equivalents | (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	25,004	53,537
Commercial paper | (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Commercial paper | (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	25,004	53,537
Commercial paper | (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
U.S. Government-sponsored enterprise
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	21,835	17,935
U.S. Government-sponsored enterprise | (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	17,935
U.S. Government-sponsored enterprise | (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	21,835	0
U.S. Government-sponsored enterprise | (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
U.S. Treasury securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	12,728
U.S. Treasury securities | (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	12,728
U.S. Treasury securities | (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0
U.S. Treasury securities | (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0
Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	51,320	15,729
Corporate debt securities | (Level 1)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	0	0
Corporate debt securities | (Level 2)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	51,320	15,729
Corporate debt securities | (Level 3)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Oct. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfer between level 1 and level 2 assets	$ 0		$ 0
Warrants exercise price (USD per share)	$ 73.73
Outstanding warrants	98,965
Series A warrants
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Warrants issue to purchase common stock	93,470		8,598,076
Warrants exercise price (USD per share)	$ 3.50
Warrants initial value				$ 5,200,000
Warrants expired			13,450
Outstanding warrants	417,315
Series A warrants | Secondary Public Offering
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Public offering period	5 years	5 years
Warrants issue to purchase common stock	4,630,000	4,630,000
Warrants exercise price (USD per share)	$ 3.50	$ 3.50

Fair Value Measurements - Sch_2

Fair Value Measurements - Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants (Detail) - Series A warrants	Sep. 30, 2019	Dec. 31, 2018
Risk-free interest rate
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	0.016	0.030
Expected dividend yield
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	0	0
Expected volatility
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	0.833	0.783
Expected Term
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Expected term (in years)	3 years	3 years 9 months 18 days

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Total Level 3 Financial Assets (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Balance at beginning of period	$ 17,926	$ 5,432
Increase in fair value included in change in fair value of common stock warrants	10,849	69,042
Decrease in fair value from warrants exercised during the period	(5,492)	(53,831)
Balance at end of period	$ 23,283	$ 20,643

Fair Value Measurements - Sch_3

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis Footnote (Detail)	9 Months Ended
	Sep. 30, 2019
Maximum
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents maturity term	3 months

Leases - Additional Information

Leases - Additional Information (Detail) $ in Thousands	Sep. 30, 2019USD ($)	Jun. 30, 2019USD ($)	May 31, 2019ft²	Mar. 31, 2019USD ($)ft²	Jan. 31, 2019ft²	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Liability	$ 21,209
Deferred rent—long-term							$ (3,799)
Operating lease right-of-use assets	$ 16,577
10935 Vista Sorrento Parkway, San Diego, California
Lessee, Lease, Description [Line Items]
Operating Lease, Liability		$ 200		$ 3,100
Area of office space leased | ft²			33,681		25,332
Operating lease right-of-use assets				$ 3,100
10935 Vista Sorrento Parkway, San Diego, California | Maximum
Lessee, Lease, Description [Line Items]
Operating lease extension period	4 years
6495 Marindustry Place, San Diego, California
Lessee, Lease, Description [Line Items]
Operating Lease, Liability		3,400
Area of office space leased | ft²				40,490
Operating lease right-of-use assets		3,400
6495 Marindustry Place, San Diego, California | Minimum
Lessee, Lease, Description [Line Items]
Operating lease extension period	3 years
6495 Marindustry Place, San Diego, California | Maximum
Lessee, Lease, Description [Line Items]
Operating lease extension period	5 years
Accounting Standards Update 2016-02
Lessee, Lease, Description [Line Items]
Operating Lease, Liability						$ 12,400
Maximum lease period to not recognize right of use assets or lease liabilities						12 months
Operating lease right-of-use assets						$ 12,400
Accounting Standards Update 2016-02 | Difference Between Leases Guidance in Effect Before and After Topic 842
Lessee, Lease, Description [Line Items]
Deferred rent—long-term						3,800
Accounting Standards Update 2016-02 | Difference Between Leases Guidance in Effect Before and After Topic 842 | Other Current Liabilities
Lessee, Lease, Description [Line Items]
Deferred rent, current						$ 1,000
Vista Sorrento Original Lease | 10935 Vista Sorrento Parkway, San Diego, California
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets		$ 4,500

Leases Schedule of Future Minim

Leases Schedule of Future Minimum Payments Under Non-cancellable Operating Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
2019 (remaining)	$ 867
2020	6,831
2021	7,100
2022	5,880
2023	1,991
Thereafter	1,577
Total future minimum lease payments	24,246
Less: amount representing interest	(3,037)
Present value of future minimum lease payments	21,209
Less: current portion of operating lease liabilities	(5,951)
Operating lease liabilities - long-term	$ 15,258

Term Loan Agreement - Additiona

Term Loan Agreement - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Debt Instrument [Line Items]
Outstanding warrants	98,965	98,965
Warrants exercise price (USD per share)	$ 73.73	$ 73.73
Term Loan Agreement
Debt Instrument [Line Items]
Loan outstanding	$ 0	$ 0	$ 0	$ 82,700,000
Accrued interest				1,100,000
Associated financing fees				$ 5,000,000
Interest rate	11.50%	11.50%
Interest payable as cash	9.50%	9.50%
Compounded interest payable	2.00%	2.00%
Interest-only payments description	Under the Term Loan Agreement, interest was payable at the Company’s option, (i) in cash at a rate of 11.5% per annum, or (ii) at a rate of 9.5% of the 11.5% per annum in cash and 2.0% of the 11.5% per annum (PIK Loan) to be added to the principal of the loan and subject to accruing interest.
Maturity date for interest-only payment	Dec. 31, 2019
Term Loan Amendments
Debt Instrument [Line Items]
Warrants issue to purchase common stock	193,788	193,788
Contractual life (years)		10 years
Outstanding warrants	193,788	193,788
Warrants exercise price (USD per share)	$ 23.50	$ 23.50

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding warrants			98,965			98,965
Warrants exercise price (USD per share)			$ 73.73			$ 73.73
Gross proceeds from secondary public offering				$ 115,000	$ 69,000
Stock-based compensation expenses			$ 17,230	$ 9,537		$ 39,386	$ 13,427
Total stock-based compensation expense capitalized as part of cost of inventory						$ 800		$ 400
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance under the ESPP (in shares)	5,000,000	5,500,000
Shares granted (in shares)	1,644,715	3,389,300				2,916,906	3,661,220
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares issued (in shares)			439,646			1,213,428		136,042
Common stock warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock shares issued (in shares)			200			93,470		8,603,321
Secondary Public Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares offered for public offering (in shares)				4,035,085	34,500,000
Shares offering price per share (in dollars per share)				$ 28.50	$ 2		$ 28.50
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance under the ESPP (in shares)		2,000,000
Offering period			2 years
Purchase period			four six-month
Purchase of common stock under ESPP (in shares)						168,165		80,581
December 2017 | 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)		811,800
First anniversary | 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	25.00%						25.00%
Monthly vesting over following 3 years | 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	75.00%						75.00%
First anniversary | 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		50.00%
Monthly vesting over following year | 2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		50.00%
Series A warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding warrants			417,315			417,315
Warrants exercise price (USD per share)			$ 3.50			$ 3.50
Series A warrants | Secondary Public Offering
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Warrants exercise price (USD per share)			$ 3.50			$ 3.50		$ 3.50
Term Loan Amendments
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding warrants			193,788			193,788
Warrants exercise price (USD per share)			$ 23.50			$ 23.50

Stockholders' Equity - Schedule

Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Future Issuance (Detail) shares in Thousands	Sep. 30, 2019shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	13,085
Shares underlying outstanding warrants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	710
Shares underlying outstanding stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	7,358
Shares authorized for future equity award grants
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	3,165
Shares authorized for issuance pursuant to awards granted under the ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for future issuance	1,852

Stockholders' Equity - Schedu_2

Stockholders' Equity - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in usd per share)	$ 38.74	$ 21.77	$ 39.08	$ 12.35
Risk-free interest rate	1.70%	2.80%	2.10%	2.80%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	71.80%	70.50%	71.80%	71.40%
Expected term (in years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years	5 years 8 months 12 days
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value (in usd per share)			$ 33.49	$ 9.62
Risk-free interest rate			2.30%	2.40%
Expected dividend yield			0.00%	0.00%
Expected volatility			75.90%	77.00%
Expected term (in years)			1 year 3 months 18 days	1 year 3 months 18 days

Stockholders' Equity - Summary

Stockholders' Equity - Summary for Allocation of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 17,230	$ 9,537	$ 39,386	$ 13,427
Cost of sales
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	1,751	784	4,178	1,129
Selling, general & administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	13,110	6,821	29,060	9,833
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost	$ 2,369	$ 1,932	$ 6,148	$ 2,465

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - legal_matter	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Number of legal proceedings, regulatory matters, or other, disputes or claims	0	0