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Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2018	Jul. 26, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q2
Trading Symbol	TNDM
Entity Registrant Name	TANDEM DIABETES CARE INC
Entity Central Index Key	0001438133
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		53,190,159

CONDENSED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 50,548	$ 13,700
Short-term investments	35,957	479
Accounts receivable, net	13,914	20,793
Inventory, net	24,912	26,993
Prepaid and other current assets	3,012	2,191
Total current assets	128,343	64,156
Property and equipment, net	18,212	19,631
Restricted cash - long term	10,000	10,000
Other long-term assets	145	102
Total assets	157,994	95,346
Current liabilities:
Accounts payable	3,646	5,150
Accrued expense	4,278	2,832
Employee-related liabilities	13,641	14,488
Deferred revenue	2,964	2,526
Common stock warrants	12,291	5,432
Other current liabilities	5,687	5,657
Total current liabilities	42,507	36,085
Notes payable—long-term	77,100	76,541
Deferred rent—long-term	4,250	4,687
Other long-term liabilities	8,132	7,181
Total liabilities	131,989	124,494
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value; 100,000 shares authorized as of June 30, 2018 and December 31, 2017, 53,186 and 10,119 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively.	53	10
Additional paid-in capital	595,463	448,455
Accumulated other comprehensive income	6
Accumulated deficit	(569,517)	(477,613)
Total stockholders’ equity (deficit)	26,005	(29,148)
Total liabilities and stockholders’ equity (deficit)	157,994	95,346
Patents [Member]
Current assets:
Patents, net	$ 1,294	$ 1,457

CONDENSED BALANCE SHEETS (Parenthetical) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	53,186,000	10,119,000
Common stock, shares outstanding	53,186,000	10,119,000

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) - USD ($)
shares in Thousands, $ in Thousands

3 Months Ended

6 Months Ended

Jun. 30, 2018

Jun. 30, 2017

Jun. 30, 2018

Jun. 30, 2017

Income Statement [Abstract]

Sales

$ 34,126

$ 21,327

$ 61,402

$ 40,303

Cost of sales

19,039

13,325

34,912

25,549

Gross profit

15,087

8,002

26,490

14,754

Operating expenses:

Selling, general and administrative

22,628

22,104

43,541

44,952

Research and development

6,456

4,866

12,431

9,996

Total operating expenses

29,084

26,970

55,972

54,948

Operating loss

(13,997)

(18,968)

(29,482)

(40,194)

Other income (expense), net:

Interest and other income

299

390

119

Interest and other expense

(3,112)

(2,892)

(6,184)

(5,518)

Change in fair value of stock warrants

(42,549)

(56,777)

Total other expense, net

(45,362)

(2,832)

(62,571)

(5,399)

Net loss

(59,359)

(21,800)

(92,053)

(45,593)

Other comprehensive loss:

Unrealized gain on short-term investments

Comprehensive loss

$ (59,353)

$ (21,800)

$ (92,047)

$ (45,592)

Net loss per share, basic and diluted

^[1]

$ (1.17)

$ (4.36)

$ (2.32)

$ (11.12)

Weighted average shares used to compute basic and diluted net loss per share

^[1]

50,948

5,004

39,594

4,101

[1]	The issued and outstanding shares of common stock have been restated for all periods presented to reflect the effects of the 1-for-10 reverse stock split, which was effective on October 9, 2017.

CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) (Parenthetical)		6 Months Ended
	Oct. 09, 2017	Jun. 30, 2018
Income Statement [Abstract]
Reverse stock split description		1-for-10 reverse stock split
Reverse stock split, conversion ratio	0.1

CONDENSED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended		27 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Operating activities
Net loss		$ (92,053)	$ (45,593)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization expense		2,898	3,016
Interest expense related to amortization of debt discount and debt issuance costs		1,387	817
Provision for allowance for doubtful accounts		745	417
Provision for inventory reserve		184	265
Payment in kind interest accrual of notes payable			817	$ 2,700
Change in fair value of common stock warrants	$ 42,549	56,777
Amortization of discount on short-term investments		298	(16)
Stock-based compensation expense		3,890	8,110
Other		151	66
Changes in operating assets and liabilities:
Accounts receivable, net		6,135	1,726
Inventory, net		1,958	(4,797)
Prepaid and other current assets		(821)	1,534
Other long-term assets		(43)	(20)
Accounts payable		(1,733)	(447)
Accrued expense		1,446	(873)
Employee-related liabilities		(848)	2,506
Deferred revenue		439	(1,350)
Other current liabilities		(49)	(850)
Deferred rent		(359)	(266)
Other long-term liabilities		603	(539)
Net cash used in operating activities		(18,995)	(35,477)
Investing activities
Purchase of short-term investments		(40,500)
Proceeds from sales and maturities of short-term investments		4,250	8,500
Purchase of property and equipment		(1,087)	(4,055)
Net cash provided by (used in) investing activities		(37,337)	4,445
Financing activities
Proceeds from public offering, net of offering costs		64,008	21,135
Proceeds from exercise of warrants		29,164
Proceeds from common stock issued under employee benefit plans		8	570
Net cash provided by financing activities		93,180	21,705
Net increase in cash and cash equivalents and restricted cash		36,848	(9,327)
Cash and cash equivalents and restricted cash at beginning of period		23,700	46,678
Cash and cash equivalents and restricted cash at end of period	$ 60,548	60,548	37,351	$ 23,700
Supplemental disclosures of cash flow information
Interest paid		4,784	3,882
Supplemental schedule of noncash investing and financing activities
Lease incentive - lessor-paid tenant improvements			2,784
Debt discount included in other long-term liabilities		4,964	4,095
Common stock warrants issued in connection with term loan			3,331
Property and equipment included in accounts payable		$ 92	$ 60

Organization and Basis of Presentation	6 Months Ended
Organization and Basis of Presentation	Jun. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Basis of Presentation	1. Organization and Basis of Presentation The Company Tandem Diabetes Care, Inc. is a medical device company focused on 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. The Company manufactures and sells insulin pump products in the United States that are designed to address large and differentiated needs of the insulin-dependent diabetes market. The Company’s manufacturing and sales activities primarily focus on the t:slim X2 Insulin Delivery System, or t:slim X2, the next-generation flagship product that is updatable and designed to display Dexcom G5 continuous glucose monitoring, or CGM, sensor information directly on the pump Home Screen. 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 selling 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’s insulin pump products are compatible with the Tandem Device Updater, a Macand PC-compatible tool for the remote update of Tandem insulin pump software. The Company began commercial sales of its first product, t:slim, in August 2012. During 2015, the Company commenced commercial sales of two additional insulin pumps: t:flex in May 2015 and t:slim G4 in September 2015. In October 2016, the Company commenced commercial sales of t:slim X2 and discontinued new sales of t:slim. In September 2017, the Company commenced commercial sales of t:slim X2 with Dexcom G5 Mobile CGM integration, or t:slim X2 with G5, and discontinued new sales of t:slim G4. Because the t:slim X2 hardware platform has represented nearly 100% of new pump shipments, the Company discontinued marketing and sales of new t:flex pumps in the third quarter of 2018. The Company will continue to provide ongoing service and support to existing t:slim, t:slim G4 and t:flex customers. In July 2016, the Company launched a Technology Upgrade Program that provided eligible t:slim and t:slim G4 customers a path to obtain t:slim X2, or, as of September 2017, t:slim X2 with G5. Participating customers had the right to exchange their original t:slim and t:slim G4 for a t:slim X2 or t:slim X2 with G5, under a variable pricing structure. The Technology Upgrade Program expired on September 30, 2017. The Company has incurred operating losses since its inception and, as reflected in the accompanying financial statements, the Company has an accumulated deficit of $569.5 million as of June 30, 2018, which includes a net loss of $92.1 million for the six months ended June 30, 2018. The Company primarily funded its operations through private and public equity and debt financing. Management expects operating losses and negative cash flows to continue for at least the next 12 months. As of June 30, 2018, the Company had $96.5 million in cash and cash equivalents and short-term investments, which included $10.0 million of restricted cash. Management believes that the cash on hand will be sufficient to satisfy its liquidity requirements for at least the next 12 months. The Company’s ability to execute on its business strategy, meet its future liquidity requirements, satisfy the covenants under the Amended and Restated Term Loan Agreement with Capital Royalty Partners (“Term Loan Agreement”) (see Note 6, “Term Loan Agreement”) 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, increase gross profits from higher sales of infusion sets, maximize manufacturing efficiencies, and leverage the investments made in its sales, clinical, marketing and customer support organizations. The Company has primarily funded its operations through private and public equity and debt financing. The Company may in the future seek additional capital from public or private offerings of its capital stock, it may elect to repay, restructure or refinance its existing indebtedness, or it may elect to borrow additional amounts under new credit lines 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 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 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 financial statements should be read in conjunction with the Company’s audited financial statements and accompanying footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“Annual Report”), from which the balance sheet information herein was derived. These unaudited condensed financial statements exclude disclosures required by U.S. GAAP for complete financial statements.

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

There have been no material changes in our significant accounting policies during the six months ended June 30, 2018, as compared with those disclosed in the Annual Report other than adoption of the new revenue recognition standard (“Revenue from Contracts with Customers Standard”).

Use of Estimates

The preparation of the financial statements in conformity with U.S. GAAP requires management to make informed estimates and assumptions that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosure of contingent assets and liabilities in the Company’s financial statements and accompanying footnotes as of the date of the financial statements. Actual results could materially differ from those estimates and assumptions.

Segment Reporting

Operating segments are identified as components of an enterprise about which segment discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and managed its business as one segment, operating in the United States.

Restricted Cash

The Company recorded $10.0 million of restricted cash as of both June 30, 2018 and December 31, 2017, for the minimum cash balance requirement in connection with the Term Loan Agreement (see Note 6, “Term Loan Agreement”). In January 2018, the Company adopted new guidance from the Financial Accounting Standards Board (“FASB”) that clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows. As a result, the restricted cash balance is now included as a component of cash and cash equivalents on the statement of cash flows in all periods presented.

Accounts Receivable

The Company grants credit to various customers in the ordinary course of business. 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 carrying amounts of cash and cash equivalents, accounts receivable, accounts payable, accrued expense, 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. Based on the borrowing rates currently available for loans with similar terms, the Company believes the fair value of its long-term notes payable approximates its carrying value. The estimated fair value of certain of the Company’s common stock warrants is determined using the Black-Scholes pricing model as of June 30, 2018 and December 31, 2017 (see Note 5, “Fair Value Measurements”).

Revenue Recognition

Revenue is generated primarily from sales in the United States of insulin pumps, disposable cartridges and infusion sets to individual customers and third-party distributors that resell the product to insulin-dependent diabetes customers. The Company is paid directly by customers who use the products, distributors and third-party insurance payors.

In January 2018, the Company adopted Revenue from Contracts with Customers Standard that supersedes 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 is not impacted by the new guidance. As a result, on January 1, 2018, the Company recorded a net reduction to accumulated deficit in the amount of $149,000, reflecting 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 upon delivery, while access to the complementary products (t:connect cloud-based data management application and the Tandem Device Updater) are considered performance obligations satisfied over the 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 margin approach and then allocates the residual to the insulin pumps. At June 30, 2018 and December 31, 2017, $2.3 million and $2.0 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. Under the new guidance, the allowance for product returns is recorded as a reduction of revenue and an increase in deferred revenue in the period in which the related sale is recorded. Historically, the allowance was recorded as a reduction of revenue and accounts receivable. The amount recorded on the Company’s balance sheets for product return allowance was $0.1 million and $0.2 million at June 30, 2018 and December 31, 2017, respectively. Actual product returns have not differed materially from estimated amounts reserved in the accompanying condensed 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 June 30, 2018 and December 31, 2017, the warranty reserve was $6.3 million and $5.6 million, respectively. The following table provides a reconciliation of the change in product warranty liabilities from December 31, 2017 through June 30, 2018 (in thousands):

Balance at December 31, 2017	$	5,640
Provision for warranties issued during the period		3,390
Settlements made during the period		(3,869	)
Increases in warranty estimates		1,159
Balance at June 30, 2018	$	6,320

Current portion	$	3,152
Non-current portion		3,168
Total	$	6,320

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 2013 Stock Incentive Plan (“2013 Plan”) and shares issued under the Company’s 2013 Employee Stock Purchase Plan (“ESPP”) using a Black-Scholes option-pricing model on the date of grant. The Black-Scholes option-pricing model requires the use of subjective assumptions about a number of key variables, including stock price volatility, expected term, 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 common shares that were outstanding for the period, without consideration for common stock equivalents. Diluted loss per share is calculated in accordance with the treasury stock method and reflects the potential dilution that would occur if securities or other contracts to issue common stock were exercised or converted to common stock. Dilutive common share equivalents are comprised of warrants, potential awards granted pursuant to the ESPP, and options outstanding under the Company’s other equity incentive plans. For warrants that are recorded as a liability in the accompanying balance sheet, the calculation of diluted 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 such securities are dilutive to loss per share for the period, an adjustment to net loss used in the calculation is required 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, 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.

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				Six Months Ended
	June 30,				June 30,
	2018		2017⁽¹⁾		2018		2017⁽¹⁾
Warrants for common stock		628		-		628		-
Common stock options		2,166		-		1,852		-
ESPP		1		-		1		-
		2,795		-		2,481		-

(1)	As of June 30, 2017 there were no outstanding common share equivalents that were dilutive based on their respective exercise prices compared to the market value of the Company’s common stock on that date.

Reclassifications

Certain reclassifications of prior year amounts have been made to conform to the current year presentation.

Recent Accounting Pronouncements

In June 2016, FASB issued a new credit loss standard that changes the impairment model for most financial assets and certain other instruments. The standard is effective for public business entities for annual periods beginning after December 15, 2019, and interim periods within those years. Early adoption is permitted for all entities for annual periods beginning after December 15, 2018, and interim periods within those years. The Company is in the process of assessing the impact of the adoption of the standard on its financial statements.

In February 2016, FASB issued final guidance for lease accounting. The new accounting standard requires lessees to recognize right-of-use assets and corresponding lease liabilities for all leases with lease terms of greater than twelve months. It also changes the definition of a lease and expands the disclosure requirements of lease arrangements. The new accounting standard must be adopted using the modified retrospective approach and will be effective for the Company starting in the first quarter of fiscal 2019. Early adoption is permitted. The Company is in the process of assessing the impact of the adoption of the standard on its financial statements.

In March 2018, the FASB issued Accounting Standards Update No. 2018-05, Income taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin No. 118 regarding Income Tax Accounting Implications of the Tax Cuts and Jobs Act. The Company recognized the income tax effects of the 2017 Tax Act in its 2017 financial statements for which the accounting under ASC Topic 740 is incomplete, but a reasonable estimate could be determined. The tax effects of certain provisions of the 2017 Tax Act, such as the deductibility of compensation in excess of $1 million for certain employees, and limitations on executive compensation, requires further analysis. The Company is in the process of assessing the impact of the adoption of the standard on its financial statements.

Short-Term Investments

6 Months Ended

Jun. 30, 2018

Investments Debt And Equity Securities [Abstract]

Short-Term Investments

3. Short-Term Investments

The Company invests in investment securities, principally debt instruments of financial institutions and corporations with strong credit ratings. The following represents a summary of the estimated fair value of short-term investments as of June 30, 2018 and December 31, 2017 (in thousands):

At June 30, 2018	Maturity (in years)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Available-for-sale investment securities:
Commercial paper	Less than 1	$	35,952	$	7	$	(2	)	$	35,957
Total		$	35,952	$	7	$	(2	)	$	35,957

At December 31, 2017	Maturity (in years)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Trading securities:
Mutual funds held for nonqualified deferred compensation plan participants		$	459	$	20	$	—	$	479
Total		$	459	$	20	$	—	$	479

Inventory

6 Months Ended

Jun. 30, 2018

Inventory Disclosure [Abstract]

Inventory

4. Inventory

Inventory consisted of the following as of June 30, 2018 and December 31, 2017 (in thousands):

	June 30,		December 31,
	2018		2017
Raw materials	$	10,265	$	10,328
Work in process		3,125		3,812
Finished goods		11,522		12,853
Total	$	24,912	$	26,993

Fair Value Measurements

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

5. Fair Value Measurements

Authoritative guidance on fair value measurements defines fair value, establishes a consistent framework for measuring fair value, and expands disclosures for 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 establishes 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 June 30, 2018 and December 31, 2017, 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
			June 30, 2018
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents (1)	$	60,548	$	60,548	$	—	$	—
Commercial paper		35,957	—			35,957	—
Total assets	$	96,505	$	60,548	$	35,957	$	—

Liabilities
Common stock warrants	$	12,291	$	—	$	—	$	12,291
Total liabilities	$	12,291	$	—	$	—	$	12,291

			Fair Value Measurements at
			December 31, 2017
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents (1)	$	23,700	$	23,700	$	—	$	—
Mutual funds held for nonqualified deferred compensation plan participants (2)		479		479		—		—
Total assets	$	24,179	$	24,179	$	—	$	—
Liabilities
Common stock warrants	$	5,432	$	—	$	—	$	5,432
Deferred compensation (2)		479		479		—		-
Total liabilities	$	5,911	$	479	$	—	$	5,432

(1)

Generally, cash equivalents include money market funds and investments with a maturity of three months or less from the date of purchase. This asset is included as a component of cash and cash equivalents on the balance sheet, of which $10.0 million is classified as restricted cash – long-term as of both June 30, 2018 and December 31, 2017.

(2)

The deferred compensation plan was directed by the Company and structured as a Rabbi Trust for the benefit of certain executives and non-employee directors. The investment assets of the Rabbi Trust were valued using quoted market prices multiplied by the number of shares held in each trust account. The related deferred compensation liability represents the fair value of the investment assets. The Company cancelled the deferred compensation plan in 2017 and all deferred compensation amounts were distributed to participants during the quarter ended June 30, 2018.

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 six months ended June 30, 2018.

The Company’s Level 3 liabilities at June 30, 2018 included the Series A warrants issued by the Company in connection with its public offering of common stock in October 2017. Level 3 liabilities at December 31, 2017 included the Series A and Series B warrants issued by the Company in connection with the October 2017 offering. 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 B warrants had a term of six months 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 and Series B warrants were initially valued in the aggregate amount of $6.5 million on the date of issuance utilizing a Black-Scholes pricing model. As of June 30, 2018, there were Series A warrants to purchase 628,235 shares outstanding and no Series B warrants outstanding (see Note 7, “Stockholders’ Equity”).

The Company reassesses the fair value of the outstanding Series A and Series B warrants at each reporting date utilizing a Black-Scholes pricing model. Inputs used in the pricing model include estimates of stock price volatility, expected warrant life 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 common stock warrants at June 30, 2018 and December 31, 2017 are presented below:

	Series A Warrants
	June 30, 2018			December 31, 2017
Risk-free interest rate		2.7	%		2.2	%
Expected dividend yield		0.0	%		0.0	%
Expected volatility		80.9	%		63.5	%
Expected term (in years)		4.3			4.8

	Series B Warrants
	June 30, 2018	December 31, 2017
Risk-free interest rate	N/A		1.4	%
Expected dividend yield	N/A		0.0	%
Expected volatility	N/A		80.3	%
Expected term (in years)	N/A		0.3

(1)	As of June 30, 2018, there were no Series B warrants outstanding.

The following table presents a summary of changes in the fair value of the Company’s Level 3 financial assets for the quarter ended June 30, 2018:

Balance at December 31, 2017	$	5,432
Decrease in fair value from warrants exercised during the period		(49,919	)
Increase in fair value included in change in fair value of common stock warrants		56,778
Balance at June 30, 2018	$	12,291

During the six months ended June 30, 2018, the Company issued 8,485,871 shares of common stock upon the exercise of Series A and Series B warrants and 13,450 Series B warrants expired unexercised. As a result, there were 628,235 Series A warrants to purchase common stock from the October 2017 financing outstanding as of June 30, 2018.

- Definition

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

+ References + Details

Term Loan Agreement	6 Months Ended
Term Loan Agreement	Jun. 30, 2018
Debt Disclosure [Abstract]
Term Loan Agreement	6. Term Loan Agreement The Company had $82.7 million of aggregate borrowings outstanding under the Term Loan Agreement as of June 30, 2018 and December 31, 2017, respectively. Under the Term Loan Agreement, interest is 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 (the “PIK Loan”) to be added to the principal of the loan and subject to accruing interest. Interest-only payments are due quarterly on March 31, June 30, September 30 and December 31 of each year of the interest-only payment period, which ends on December 31, 2019. The principal balance is due in full at the end of the term of the loan, which is March 31, 2020 (the “Maturity Date”). The Company had elected to pay interest in cash at a rate of 11.5% per annum through September 30, 2015. From October 1, 2015 through December 31, 2017, the Company elected to pay interest in cash at a rate of 9.5% per annum and for a rate of 2.0% per annum to be added to the principal of the loan. As a result, $2.7 million was added to the principal of the loan during that time period (the “PIK Loans”). The term loan is collateralized by all assets of the Company. The principal financial covenants require that the Company attain minimum annual revenues of $95.0 million in 2018 and each year thereafter until the Maturity Date. Pursuant to Amendment No. 3 to the Term Loan Agreement (the “Third Amendment”), the Company agreed to pay, on the earlier of (i) the Maturity Date, (ii) the date that the loan under the Term Loan Agreement becomes due, and (iii) the date on which the Company makes a voluntary pre-payment of the loan, a financing fee equal to 3.0% of the sum of (x) the aggregate amount drawn under the Third Amendment, which is $50.0 million, and (y) any PIK Loans issued in relation to the Third Amendment (collectively, the “Back End Financing Fee”). In March 2017, the Company entered into Amendment No. 4 to the Term Loan Agreement (the “Fourth Amendment”), which included a limited waiver of a potential event of default that could have resulted from the explanatory paragraph in the audit report of its independent registered public accounting firm contained in its financial statements for the year ended December 31, 2016. In consideration for the waiver, the Company agreed to: (i) issue Capital Royalty Partners ten-year warrants to purchase an aggregate of 193,788 shares of the Company’s common stock at an exercise price of $23.50 per share, (ii) increase the Company’s minimum cash balance requirement under the Term Loan Agreement from $2.0 million to $10.0 million, (iii) provide Capital Royalty Partners the same information it makes available to its board of directors, subject to limited exceptions, and (iv) not incur additional third party indebtedness secured solely by accounts receivable, inventory and cash. Furthermore, the Company agreed to increase the Back End Financing Fee to 5.0% of the entire aggregate principal amount of borrowings outstanding, including total PIK Loans issued, under the Term Loan Agreement, which was $82.7 million as of December 31, 2017. The Back End Financing Fee is payable at maturity of the Company’s loans and on the principal amount of any loans for which it makes an optional prepayment, and may be payable in connection with asset sales not permitted under the Term Loan Agreement or a change of control. In February 2018, the Company entered into Amendment No. 5 to the Term Loan Agreement (the “Fifth Amendment”), which included a limited advance waiver of a potential event of default that could have resulted from a qualification regarding the Company’s ability to continue as a going concern in the audit report for the year ended December 31, 2017. The Fifth Amendment included a covenant requiring the Company to complete a financing in which gross proceeds from the sale of equity securities was at least $20.0 million, no later than August 30, 2018, which covenant was satisfied in February 2018. In addition, the Company agreed to increase the Back End Financing Fee from 5.0% to 6.0% of the entire aggregate principal amount of borrowings outstanding, including total PIK Loans issued, under the Term Loan Agreement. As of June 30, 2018, and December 31, 2017, the Company had accrued $5.0 million and $4.1 million for the Back End Financing Fee in other long-term liabilities and as contra-debt in notes payable-long-term on the accompanying balance sheet. The Company treated the execution of each of the Third, Fourth and Fifth Amendments as a modification for accounting purposes. The present value of the future cash flows under these amendments did not exceed the present value of the future cash flows under the previous terms by more than 10%. The Back End Financing Fee and the remaining balance of debt issuance costs and debt discount of the loan are amortized to interest expense over the remaining term using the effective interest method.

Stockholders' Equity

6 Months Ended

Jun. 30, 2018

Equity [Abstract]

Stockholders' Equity

7. Stockholders’ Equity

Public Offerings

In the first quarter of 2017, the Company completed a public offering of 1,850,000 shares of its common stock at a public offering price of $12.50 per share. The gross proceeds to the Company from the offering were $23.1 million, before deducting underwriting discounts and commissions and other offering expenses payable by the Company.

From July 2017 through September 2017, the Company sold 464,108 shares of its common stock under its “at-the-market” offering program at prices ranging from $5.64 to $10.54. The gross proceeds from the offering were $4.3 million, before deducting underwriting discounts and commissions and other offering expenses.

In October 2017, the Company completed a public offering, pursuant to which it sold 4,630,000 shares of its common stock, Series A warrants to purchase up to 4,630,000 shares and Series B warrants to purchase up to 4,630,000 shares at a public offering price of $3.50 per share and accompanying warrants. The gross proceeds from the public offering were approximately $16.2 million, before deducting underwriting discounts and commissions and other offering expenses. As of June 30, 2018, the Company had issued 8,485,871 shares upon exercise of Series A and Series B warrants, which resulted in gross proceeds to the Company of $29.2 million. As of June 30, 2018, there were 628,235 Series A warrants outstanding and no Series B warrants outstanding. During the three months ended June 30, 2018, 13,450 Series B warrants expired unexercised.

In the first quarter of 2018, the Company completed a public offering of 34,500,000 shares of its common stock at a public offering price of $2.00 per share. The gross proceeds to the Company from the offering were $69.0 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 June 30, 2018 (in thousands):

Shares underlying outstanding warrants		921
Shares underlying outstanding stock options		5,558
Shares authorized for future equity award grants		1,317
Shares authorized for issuance as ESPP awards		2,101
		9,897

In June 2018, the Company received approval from its stockholders to increase the number of shares of common stock reserved under the 2013 Plan by 5,500,000 shares. The Company issued 8,485,871 shares of its common stock upon the exercise of warrants, and 564 shares of its common stock upon the exercise of stock options during the six months ended June 30, 2018. The Company did not issue any shares of its common stock upon the exercise of warrants, and issued 24,406 shares of its common stock upon the exercise of stock options during the year ended December 31, 2017.

The ESPP enables eligible employees to purchase shares of 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 began in May and November of each year. The Company announced the suspension of 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 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 will be November 15, 2018. As a result of the previous suspension of the ESPP, no shares of common stock were purchased under the ESPP during the six months ended June 30, 2018. There were 38,929 shares of common stock purchased under the ESPP during the year ended December 31, 2017.

Stock-Based Compensation

In June 2018, the Company issued options to purchase 811,800 shares of common stock under the 2013 Plan, which were originally granted on December 1, 2017, subject to and conditioned upon the approval by its stockholders of an increase in the number of shares authorized under the 2013 Plan. In addition, in June 2018, the Company granted options to purchase 3,339,300 shares of common stock under the 2013 Plan. These options have an exercise price equal to the closing price of the common stock on the respective grant date, and generally vest 50% on the first anniversary of the grant date, with the balance vesting monthly over the following year.

The assumptions used in the Black-Scholes option-pricing model are as follows:

	Stock Options
	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2018			2017			2018			2017
Weighted average grant date fair value (per share)	$	11.97		$	5.10		$	11.89		$	5.20
Risk-free interest rate		2.8	%		1.9	%		2.8	%		1.9	%
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%
Expected volatility		71.5	%		60.0	%		71.4	%		60.0	%
Expected term (in years)		5.6			6.1			5.7			6.1

	ESPP
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018			2017⁽¹⁾				2017⁽¹⁾
Weighted average grant date fair value (per share)	$	9.62		N/A	$	9.62		N/A
Risk-free interest rate		2.4	%	N/A		2.4	%	N/A
Expected dividend yield		0.0	%	N/A		0.0	%	N/A
Expected volatility		77.0	%	N/A		77.0	%	N/A
Expected term (in years)		1.3		N/A		1.3		N/A

(1)	There were no grants made pursuant to the ESPP during the three and six months ended June 30, 2017.

The following table summarizes the allocation of stock-based compensation expense (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017		2018		2017
Cost of sales	$	180	$	529	$	345	$	758
Selling, general & administrative		2,100		4,001		3,012		6,462
Research and development		418		616		533		890
Total	$	2,698	$	5,146	$	3,890	$	8,110

The total stock-based compensation expense capitalized as part of the cost of inventory was $0.2 million and $0.2 million as of June 30, 2018 and December 31, 2017, respectively.

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and Contingencies From time to time, the Company may be subject to legal proceedings, disputes and other claims arising in the ordinary course of business, including actions with respect to intellectual property, employment, product liability and contractual matters. In connection with these matters, the Company regularly assesses the probability and range of possible loss based on the developments in these matters. A liability is recorded in the financial statements if it is determined that it is probable that a material loss has been incurred, and that the amount or range of the loss can be reasonably estimated. Because of uncertainties related to any pending actions, the Company is currently unable to predict their ultimate outcome, and, with respect to any legal proceeding or claim where no liability has been accrued, to make a meaningful estimate of the reasonably possible loss or range of loss that could result from an adverse outcome. As of June 30, 2018 and December 31, 2017, there were no legal proceedings, disputes or other claims for which a material loss was considered probable or for which the amount or range of loss was reasonably estimable.

Organization and Basis of Presentation (Policies)

6 Months Ended

Jun. 30, 2018

Accounting Policies [Abstract]

The Company

Tandem Diabetes Care, Inc. is a medical device company focused on 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.

The Company manufactures and sells insulin pump products in the United States that are designed to address large and differentiated needs of the insulin-dependent diabetes market. The Company’s manufacturing and sales activities primarily focus on the t:slim X2 Insulin Delivery System, or t:slim X2, the next-generation flagship product that is updatable and designed to display Dexcom G5 continuous glucose monitoring, or CGM, sensor information directly on the pump Home Screen. 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 selling 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’s insulin pump products are compatible with the Tandem Device Updater, a Macand PC-compatible tool for the remote update of Tandem insulin pump software.

The Company began commercial sales of its first product, t:slim, in August 2012. During 2015, the Company commenced commercial sales of two additional insulin pumps: t:flex in May 2015 and t:slim G4 in September 2015. In October 2016, the Company commenced commercial sales of t:slim X2 and discontinued new sales of t:slim. In September 2017, the Company commenced commercial sales of t:slim X2 with Dexcom G5 Mobile CGM integration, or t:slim X2 with G5, and discontinued new sales of t:slim G4. Because the t:slim X2 hardware platform has represented nearly 100% of new pump shipments, the Company discontinued marketing and sales of new t:flex pumps in the third quarter of 2018. The Company will continue to provide ongoing service and support to existing t:slim, t:slim G4 and t:flex customers.

In July 2016, the Company launched a Technology Upgrade Program that provided eligible t:slim and t:slim G4 customers a path to obtain t:slim X2, or, as of September 2017, t:slim X2 with G5. Participating customers had the right to exchange their original t:slim and t:slim G4 for a t:slim X2 or t:slim X2 with G5, under a variable pricing structure. The Technology Upgrade Program expired on September 30, 2017.

The Company has incurred operating losses since its inception and, as reflected in the accompanying financial statements, the Company has an accumulated deficit of $569.5 million as of June 30, 2018, which includes a net loss of $92.1 million for the six months ended June 30, 2018. The Company primarily funded its operations through private and public equity and debt financing. Management expects operating losses and negative cash flows to continue for at least the next 12 months.

As of June 30, 2018, the Company had $96.5 million in cash and cash equivalents and short-term investments, which included $10.0 million of restricted cash. Management believes that the cash on hand will be sufficient to satisfy its liquidity requirements for at least the next 12 months.

The Company’s ability to execute on its business strategy, meet its future liquidity requirements, satisfy the covenants under the Amended and Restated Term Loan Agreement with Capital Royalty Partners (“Term Loan Agreement”) (see Note 6, “Term Loan Agreement”) 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, increase gross profits from higher sales of infusion sets, maximize manufacturing efficiencies, and leverage the investments made in its sales, clinical, marketing and customer support organizations.

The Company has primarily funded its operations through private and public equity and debt financing. The Company may in the future seek additional capital from public or private offerings of its capital stock, it may elect to repay, restructure or refinance its existing indebtedness, or it may elect to borrow additional amounts under new credit lines 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 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 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 financial statements should be read in conjunction with the Company’s audited financial statements and accompanying footnotes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 (“Annual Report”), from which the balance sheet information herein was derived. These unaudited condensed financial statements exclude disclosures required by U.S. GAAP for complete financial statements.

Fair Value of Financial Instruments

Revenue Recognition

Warranty Reserve

Balance at December 31, 2017	$	5,640
Provision for warranties issued during the period		3,390
Settlements made during the period		(3,869	)
Increases in warranty estimates		1,159
Balance at June 30, 2018	$	6,320

Current portion	$	3,152
Non-current portion		3,168
Total	$	6,320

Stock-Based Compensation

Net Loss Per Share

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017⁽¹⁾		2018		2017⁽¹⁾
Warrants for common stock		628		-		628		-
Common stock options		2,166		-		1,852		-
ESPP		1		-		1		-
		2,795		-		2,481		-

(1)	As of June 30, 2017 there were no outstanding common share equivalents that were dilutive based on their respective exercise prices compared to the market value of the Company’s common stock on that date.

Reclassifications

Certain reclassifications of prior year amounts have been made to conform to the current year presentation.

Recent Accounting Pronouncements

Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2018

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, 2017 through June 30, 2018 (in thousands):

Balance at December 31, 2017	$	5,640
Provision for warranties issued during the period		3,390
Settlements made during the period		(3,869	)
Increases in warranty estimates		1,159
Balance at June 30, 2018	$	6,320

Current portion	$	3,152
Non-current portion		3,168
Total	$	6,320

Schedule of Anti-Dilutive Securities

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017⁽¹⁾		2018		2017⁽¹⁾
Warrants for common stock		628		-		628		-
Common stock options		2,166		-		1,852		-
ESPP		1		-		1		-
		2,795		-		2,481		-

1.	As of June 30, 2017 there were no outstanding common share equivalents that were dilutive based on their respective exercise prices compared to the market value of the Company’s common stock on that date.

Short-Term Investments (Tables)

6 Months Ended

Jun. 30, 2018

Investments Debt And Equity Securities [Abstract]

Summary of Estimated Fair Value of Short-Term Investments

At June 30, 2018	Maturity (in years)	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
Available-for-sale investment securities:
Commercial paper	Less than 1	$	35,952	$	7	$	(2	)	$	35,957
Total		$	35,952	$	7	$	(2	)	$	35,957

At December 31, 2017	Maturity (in years)	Amortized Cost		Unrealized Gain		Unrealized Loss		Estimated Fair Value
Trading securities:
Mutual funds held for nonqualified deferred compensation plan participants		$	459	$	20	$	—	$	479
Total		$	459	$	20	$	—	$	479

Inventory (Tables)

6 Months Ended

Jun. 30, 2018

Inventory Disclosure [Abstract]

Summary of Inventory

Inventory consisted of the following as of June 30, 2018 and December 31, 2017 (in thousands):

	June 30,		December 31,
	2018		2017
Raw materials	$	10,265	$	10,328
Work in process		3,125		3,812
Finished goods		11,522		12,853
Total	$	24,912	$	26,993

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis

			Fair Value Measurements at
			June 30, 2018
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents (1)	$	60,548	$	60,548	$	—	$	—
Commercial paper		35,957	—			35,957	—
Total assets	$	96,505	$	60,548	$	35,957	$	—

Liabilities
Common stock warrants	$	12,291	$	—	$	—	$	12,291
Total liabilities	$	12,291	$	—	$	—	$	12,291

			Fair Value Measurements at
			December 31, 2017
			(Level 1)		(Level 2)		(Level 3)
Assets
Cash equivalents (1)	$	23,700	$	23,700	$	—	$	—
Mutual funds held for nonqualified deferred compensation plan participants (2)		479		479		—		—
Total assets	$	24,179	$	24,179	$	—	$	—
Liabilities
Common stock warrants	$	5,432	$	—	$	—	$	5,432
Deferred compensation (2)		479		479		—		-
Total liabilities	$	5,911	$	479	$	—	$	5,432

(1)

(2)

Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants

The assumptions used to estimate the fair values of the common stock warrants at June 30, 2018 and December 31, 2017 are presented below:

	Series A Warrants
	June 30, 2018			December 31, 2017
Risk-free interest rate		2.7	%		2.2	%
Expected dividend yield		0.0	%		0.0	%
Expected volatility		80.9	%		63.5	%
Expected term (in years)		4.3			4.8

	Series B Warrants
	June 30, 2018	December 31, 2017
Risk-free interest rate	N/A		1.4	%
Expected dividend yield	N/A		0.0	%
Expected volatility	N/A		80.3	%
Expected term (in years)	N/A		0.3

(1)	As of June 30, 2018, there were no Series B warrants outstanding.

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 assets for the quarter ended June 30, 2018:

Balance at December 31, 2017	$	5,432
Decrease in fair value from warrants exercised during the period		(49,919	)
Increase in fair value included in change in fair value of common stock warrants		56,778
Balance at June 30, 2018	$	12,291

Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2018

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 June 30, 2018 (in thousands):

Shares underlying outstanding warrants		921
Shares underlying outstanding stock options		5,558
Shares authorized for future equity award grants		1,317
Shares authorized for issuance as ESPP awards		2,101
		9,897

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						Six Months Ended
	June 30,						June 30,
	2018			2017			2018			2017
Weighted average grant date fair value (per share)	$	11.97		$	5.10		$	11.89		$	5.20
Risk-free interest rate		2.8	%		1.9	%		2.8	%		1.9	%
Expected dividend yield		0.0	%		0.0	%		0.0	%		0.0	%
Expected volatility		71.5	%		60.0	%		71.4	%		60.0	%
Expected term (in years)		5.6			6.1			5.7			6.1

	ESPP
	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018			2017⁽¹⁾				2017⁽¹⁾
Weighted average grant date fair value (per share)	$	9.62		N/A	$	9.62		N/A
Risk-free interest rate		2.4	%	N/A		2.4	%	N/A
Expected dividend yield		0.0	%	N/A		0.0	%	N/A
Expected volatility		77.0	%	N/A		77.0	%	N/A
Expected term (in years)		1.3		N/A		1.3		N/A

(1)	There were no grants made pursuant to the ESPP during the three and six months ended June 30, 2017.

Summary for Allocation of Stock-Based Compensation Expense

The following table summarizes the allocation of stock-based compensation expense (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2018		2017		2018		2017
Cost of sales	$	180	$	529	$	345	$	758
Selling, general & administrative		2,100		4,001		3,012		6,462
Research and development		418		616		533		890
Total	$	2,698	$	5,146	$	3,890	$	8,110

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Organization And Basis Of Presentation [Line Items]
Operating losses and accumulated deficit	$ (569,517)		$ (569,517)		$ (477,613)
Net loss	(59,359)	$ (21,800)	(92,053)	$ (45,593)
Cash and cash equivalents and short-term investments including restricted cash	96,500		96,500
Restricted cash	$ 10,000		$ 10,000		$ 10,000
Insulin Pump [Member] \| Minimum [Member]
Organization And Basis Of Presentation [Line Items]
Expected life span term			4 years
T:slim X2 [Member]
Organization And Basis Of Presentation [Line Items]
Percentage of new pump shipments represented by product hardware platform			100.00%

Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2018 USD ($) Segment	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments \| Segment	1
Offered period for sales return	30 days
Allowance for product returns	$ 100,000		$ 200,000
Warranty reserve	$ 6,320,000		5,640,000
Description on incomplete accounting under TCJA	The Company recognized the income tax effects of the 2017 Tax Act in its 2017 financial statements for which the accounting under ASC Topic 740 is incomplete, but a reasonable estimate could be determined. The tax effects of certain provisions of the 2017 Tax Act, such as the deductibility of compensation in excess of $1 million for certain employees, and limitations on executive compensation, requires further analysis.
Warranty reserves [Member]
Summary Of Significant Accounting Policies [Line Items]
Warranty reserve	$ 6,300,000		5,600,000
Complementary products [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue	$ 2,300,000		2,000,000
Revenue performance obligations satisfied over period	4 years
Tandem Pump [Member]
Summary Of Significant Accounting Policies [Line Items]
Warranty period offered	4 years
Slim cartridges and infusion sets [Member]
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		$ 149,000
Term Loan Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 10,000,000		$ 10,000,000

Summary of Significant Accounting Policies - Summary of Reconciliation of Change in Product Warranty Liabilities (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Movement In Standard And Extended Product Warranty Increase Decrease Roll Forward
Beginning balance	$ 5,640
Provision for warranties issued during the period	3,390
Settlements made during the period	(3,869)
Increases in warranty estimates	1,159
Ending balance	6,320
Current portion	3,152
Non-current portion	$ 3,168

Summary of Significant Accounting Policies - Schedule of Anti-Dilutive Securities (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,795,000	0	2,481,000	0
Warrants for common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	628,000		628,000
Common stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	2,166,000		1,852,000
ESPP [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	1,000		1,000

Summary of Significant Accounting Policies - Schedule of Anti-Dilutive Securities (Parenthetical) (Detail) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount	2,795,000	0	2,481,000	0

Short-Term Investments - Summary of Estimated Fair Value of Short-Term Investments (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Cash Cash Equivalents And Short Term Investments [Line Items]
Short-term investments, Amortized Cost	$ 35,952	$ 459
Short-term investments, Unrealized Gain	7	20
Short-term investments, Unrealized Loss	(2)
Short-term investments, Estimated Fair Value	35,957	479
Commercial paper [Member]
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale investment securities, Amortized Cost	35,952
Available-for-sale investment securities, Unrealized Gain	7
Available-for-sale investment securities, Unrealized Loss	(2)
Available-for-sale investment securities, Estimated Fair Value	$ 35,957
Commercial paper [Member] \| Maximum [Member]
Cash Cash Equivalents And Short Term Investments [Line Items]
Available-for-sale investment securities, Maturity (in years)	1 year
Trading securities — mutual funds held for nonqualified deferred compensation plan participants [Member]
Cash Cash Equivalents And Short Term Investments [Line Items]
Trading securities, Amortized Cost		459
Trading securities, Unrealized Gain		20
Trading securities, Estimated Fair Value		$ 479

Inventory - Summary of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 10,265	$ 10,328
Work in process	3,125	3,812
Finished goods	11,522	12,853
Total	$ 24,912	$ 26,993

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	$ 96,505	$ 24,179
Total liabilities	12,291	5,911
Cash equivalents [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	60,548	23,700
Commercial paper [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	35,957
Mutual funds held for nonqualified deferred compensation plan participants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets		479
Warrants for common stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total liabilities	12,291	5,432
Deferred compensation [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total liabilities		479
Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	60,548	24,179
Total liabilities		479
Level 1 [Member] \| Cash equivalents [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	60,548	23,700
Level 1 [Member] \| Mutual funds held for nonqualified deferred compensation plan participants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets		479
Level 1 [Member] \| Deferred compensation [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total liabilities		479
Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	35,957
Level 2 [Member] \| Commercial paper [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total assets	35,957
Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total liabilities	12,291	5,432
Level 3 [Member] \| Warrants for common stock [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Total liabilities	$ 12,291	$ 5,432

Fair Value Measurements - Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Parenthetical) (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Restricted cash - long term	$ 10,000	$ 10,000
Maximum [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Cash equivalents maturity term	3 months	3 months

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Oct. 31, 2017
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Transfer between level 1 and level 2 assets	$ 0	$ 0
Series A warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Outstanding warrants	628,235	628,235
Series A warrants [Member] \| Secondary Public Offering [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issue to purchase common stock	4,630,000	4,630,000	4,630,000	4,630,000
Public offering period		5 years	5 years
Warrants exercise price	$ 3.50	$ 3.50	$ 3.50
Series B warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Outstanding warrants	0	0
Warrants to purchase common stock, expired unexercised	13,450	13,450
Series B warrants [Member] \| Secondary Public Offering [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issue to purchase common stock	0	0	4,630,000	4,630,000
Public offering period			6 months
Warrants exercise price			$ 3.50
Series A and B warrants [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Warrants issue to purchase common stock	8,485,871	8,485,871
Warrants initial value			$ 6,500,000

Fair Value Measurements - Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants (Detail)	Jun. 30, 2018	Dec. 31, 2017
Series A Warrants [Member] \| Risk Free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	2.7	2.2
Series A Warrants [Member] \| Expected Dividend Yield [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	0.0	0.0
Series A Warrants [Member] \| Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants	80.9	63.5
Series A Warrants [Member] \| Expected Term [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)	4 years 3 months 18 days	4 years 9 months 18 days
Series B Warrants [Member] \| Risk Free Interest Rate [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants		1.4
Series B Warrants [Member] \| Expected Dividend Yield [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants		0.0
Series B Warrants [Member] \| Expected Volatility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Assumptions used to estimate fair value of common stock warrants		80.3
Series B Warrants [Member] \| Expected Term [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Expected term (in years)		3 months 18 days

Fair Value Measurements - Schedule of Assumptions Used to Estimate Fair Values of Common Stock Warrants (Parenthetical) (Detail)	Jun. 30, 2018 shares
Series B warrants [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Outstanding warrants	0

Fair Value Measurements - Summary of Changes in Fair Value of Total Level 3 Financial Assets (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation Calculation Roll Forward
Balance at December 31, 2017	$ 5,432
Decrease in fair value from warrants exercised during the period	(49,919)
Increase in fair value included in change in fair value of common stock warrants	56,778
Balance at June 30, 2018	$ 12,291

Term Loan Agreement - Additional Information (Detail) - USD ($)	1 Months Ended		6 Months Ended		27 Months Ended
	Feb. 28, 2018	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Oct. 01, 2015	Sep. 30, 2015
Debt Instrument [Line Items]
Loan outstanding					$ 82,700,000
Compounded interest payable							2.00%
Additional amount borrowed				$ 817,000	2,700,000
Minimum annual revenues attainable in 2018			$ 95,000,000
Minimum annual revenues attainable after 2018			95,000,000
Term Loan Agreement [Member]
Debt Instrument [Line Items]
Loan outstanding			$ 82,700,000		82,700,000
Interest rate			11.50%					11.50%
Interest payable as cash			9.50%				9.50%
Compounded interest payable			2.00%
Interest-only payments description			Under the Term Loan Agreement, interest is 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 (the “PIK Loan”) to be added to the principal of the loan and subject to accruing interest. Interest-only payments are due quarterly on March 31, June 30, September 30 and December 31 of each year of the interest-only payment period, which ends on December 31, 2019.
Maturity date for interest-only payment			Dec. 31, 2019
Maturity date for principal balance			Mar. 31, 2020
Minimum cash balance		$ 10,000,000				$ 2,000,000
Third Amendment [Member]
Debt Instrument [Line Items]
Percentage of financing fee			3.00%
Line of credit facility amount borrowed			$ 50,000,000
Third Amendment [Member] \| Other Long Term Liabilities And As Contra-Debt In Notes Payable-Long Term [Member]
Debt Instrument [Line Items]
Accrued back end financing fee			$ 5,000,000		$ 4,100,000
Fourth Amendment [Member]
Debt Instrument [Line Items]
Warrants life		10 years
Warrants issue to purchase common stock		193,788
Warrants exercise price		$ 23.50
Prepayment fee percentage		5.00%
Present value of the future cash flows			10.00%
Fifth Amendment [Member]
Debt Instrument [Line Items]
Prepayment fee percentage	6.00%
Equity finance completion last date	Aug. 30, 2018
Fifth Amendment [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Gross proceeds from sale of equity securities on event of default occurred due to going concern qualification	$ 20,000,000

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended					6 Months Ended		12 Months Ended
	Dec. 01, 2017	Jun. 30, 2018	Oct. 31, 2017	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Gross proceeds from secondary public offering			$ 16,200		$ 69,000			$ 23,100
Gross proceeds from exercise of warrants									$ 29,164
Shares vested		50.00%
Total stock-based compensation expense capitalized as part of cost of inventory									$ 200		$ 200
Common stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares issued									564		24,406
2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of authorized for issuance		5,500,000		5,500,000					5,500,000
Series A warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding warrants		628,235		628,235					628,235
Series B warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding warrants		0		0					0
Warrants to purchase common stock, expired unexercised				13,450					13,450
Series A and B warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants issue to purchase common stock		8,485,871		8,485,871					8,485,871
Gross proceeds from exercise of warrants									$ 29,200
Common Stock [Member] \| 2013 Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted	811,800	3,339,300
Warrants for common stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares issued									8,485,871		0
Secondary Public Offering [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares offered for public offering			4,630,000		34,500,000			1,850,000
Shares offering price per share			$ 3.50		$ 2.00			$ 12.50
Secondary Public Offering [Member] \| Series A warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants issue to purchase common stock		4,630,000	4,630,000	4,630,000					4,630,000		4,630,000
Secondary Public Offering [Member] \| Series B warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Warrants issue to purchase common stock		0	4,630,000	0					0		4,630,000
At The Market Offering Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Proceeds from secondary public offering						$ 4,300
At The Market Offering Program [Member] \| Common Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares offered for public offering						464,108
At The Market Offering Program [Member] \| Common Stock [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares offering price per share						$ 5.64
At The Market Offering Program [Member] \| Common Stock [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares offering price per share						$ 10.54
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of common stock under ESPP									0		38,929
Offering Period									2 years
Purchase Period									four six-month
Shares reserved for issuance under the ESPP		2,000,000
Shares granted							0			0

Stockholders' Equity - Schedule of Shares of Common Stock Reserved for Future Issuance (Detail) shares in Thousands	Jun. 30, 2018 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	9,897
Shares underlying outstanding warrants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	921
Shares underlying outstanding stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	5,558
Shares authorized for future equity award grants [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	1,317
Shares authorized for issuance as ESPP awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for future issuance	2,101

Stockholders' Equity - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value (per share)	$ 11.97	$ 5.10	$ 11.89	$ 5.20
Risk-free interest rate	2.80%	1.90%	2.80%	1.90%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected volatility	71.50%	60.00%	71.40%	60.00%
Expected term (in years)	5 years 7 months 6 days	6 years 1 month 6 days	5 years 8 months 12 days	6 years 1 month 6 days
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average grant date fair value (per share)	$ 9.62		$ 9.62
Risk-free interest rate	2.40%		2.40%
Expected dividend yield	0.00%		0.00%
Expected volatility	77.00%		77.00%
Expected term (in years)	1 year 3 months 18 days		1 year 3 months 18 days

Stockholders' Equity - Schedule of Assumptions Used in Black-Scholes Option-Pricing Model (Parenthetical) (Detail) - shares	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
ESPP [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grants made during period	0	0

Stockholders' Equity - Summary for Allocation of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost	$ 2,698	$ 5,146	$ 3,890	$ 8,110
Cost of sales [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost	180	529	345	758
Selling, general & administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost	2,100	4,001	3,012	6,462
Research and development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Compensation cost	$ 418	$ 616	$ 533	$ 890

Commitments and Contingencies - Additional Information (Detail) - LegalMatter	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Number of legal proceedings, regulatory encounters or other matters	0	0