Inogen (INGN) 10-Q 30 Apr 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 20, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Trading Symbol	INGN
Entity Registrant Name	Inogen Inc
Entity Central Index Key	1,294,133
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		21,220,517

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 154,284	$ 142,953
Marketable securities	34,012	30,991
Accounts receivable, net	35,089	31,444
Inventories, net	22,965	18,842
Deferred cost of revenue	335	361
Income tax receivable	591	1,313
Prepaid expenses and other current assets	3,778	2,584
Total current assets	251,054	228,488
Property and equipment
Rental equipment, net	47,420	49,349
Manufacturing equipment and tooling	7,011	6,858
Computer equipment and software	5,836	5,484
Furniture and equipment	878	746
Leasehold improvements	1,603	1,598
Land and building	125	125
Construction in process	1,934	408
Total property and equipment	64,807	64,568
Less accumulated depreciation	(43,909)	(44,465)
Property and equipment, net	20,898	20,103
Goodwill	2,430	2,363
Intangible assets, net	4,456	4,717
Deferred tax asset - noncurrent	20,434	18,636
Other assets	610	765
Total assets	299,882	275,072
Current liabilities
Accounts payable and accrued expenses	24,760	20,626
Accrued payroll	6,607	6,877
Warranty reserve - current	2,829	2,505
Deferred revenue - current	3,152	3,533
Income tax payable	319	345
Total current liabilities	37,667	33,886
Long-term liabilities
Warranty reserve - noncurrent	4,416	3,666
Deferred revenue - noncurrent	10,391	9,402
Deferred tax liability - noncurrent	358	348
Other noncurrent liabilities	713	729
Total liabilities	53,545	48,031
Commitments and contingencies (Note 8)
Stockholders' equity
Common stock, $0.001 par value per share; 200,000,000 authorized; 21,214,662 and 20,976,350 shares issued and outstanding as of March 31, 2018 and December 31, 2017, respectively	21	21
Additional paid-in capital	226,635	218,109
Retained earnings	19,397	8,639
Accumulated other comprehensive income	284	272
Total stockholders' equity	246,337	227,041
Total liabilities and stockholders' equity	$ 299,882	$ 275,072

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	21,214,662	20,976,350
Common stock, shares outstanding	21,214,662	20,976,350

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue
Sales revenue	$ 73,584	$ 45,966
Rental revenue	5,467	6,534
Total revenue	79,051	52,500
Cost of revenue
Cost of sales revenue	36,948	21,913
Cost of rental revenue, including depreciation of $2,165 and $2,689, respectively	4,376	4,843
Total cost of revenue	41,324	26,756
Gross profit
Gross profit-sales revenue	36,636	24,053
Gross profit-rental revenue	1,091	1,691
Total gross profit	37,727	25,744
Operating expense
Research and development	1,416	1,309
Sales and marketing	18,038	10,529
General and administrative	9,573	8,335
Total operating expense	29,027	20,173
Income from operations	8,700	5,571
Other income (expense)
Interest income	543	101
Other income	444	207
Total other income, net	987	308
Income before benefit for income taxes	9,687	5,879
Benefit for income taxes	(1,071)	(53)
Net income	10,758	5,932
Other comprehensive income (loss), net of tax
Change in foreign currency translation adjustment	108
Change in net unrealized gains (losses) on foreign currency hedging	(249)	54
Less: reclassification adjustment for net (gains) losses included in net income	172	(57)
Total net change in unrealized gains (losses) on foreign currency hedging	(77)	(3)
Change in net unrealized gains (losses) on available-for-sale investments	(19)	64
Total other comprehensive income, net of tax	12	61
Comprehensive income	$ 10,770	$ 5,993
Basic net income per share attributable to common stockholders (Note 5)	$ 0.51	$ 0.29
Diluted net income per share attributable to common stockholders (Note 5)	$ 0.48	$ 0.27
Weighted-average number of shares used in calculating net income per share attributable to common stockholders:
Basic common shares	21,026,154	20,489,532
Diluted common shares	22,295,213	21,579,721

Consolidated Statements of Com5

Consolidated Statements of Comprehensive Income (Parenthetical) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Depreciation	$ 2,165	$ 2,689

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)
Beginning Balance at Dec. 31, 2016	$ 182,088	$ 20	$ 194,466	$ (12,363)	$ (35)
Beginning Balance, shares at Dec. 31, 2016		20,389,860
Stock-based compensation	1,891		1,891
Employee stock purchases	581		581
Employee stock purchases, shares		11,805
Stock options exercised	2,222		2,222
Stock options exercised, shares		157,412
Net income	5,932			5,932
Other comprehensive income	61				61
Ending Balance at Mar. 31, 2017	192,775	$ 20	199,160	(6,431)	26
Ending Balance, shares at Mar. 31, 2017		20,559,077
Beginning Balance at Dec. 31, 2017	227,041	$ 21	218,109	8,639	272
Beginning Balance, shares at Dec. 31, 2017		20,976,350
Stock-based compensation	3,381		3,381
Employee stock purchases	988		988
Employee stock purchases, shares		12,013
Restricted stock awards issued, shares		53,052
Vesting of restricted stock units, shares		6,206
Shares withheld related to net restricted stock settlement	(302)		(302)
Shares withheld related to net restricted stock settlement, shares		(2,553)
Stock options exercised	$ 4,459		4,459
Stock options exercised, shares	169,594	169,594
Net income	$ 10,758			10,758
Other comprehensive income	12				12
Ending Balance at Mar. 31, 2018	$ 246,337	$ 21	$ 226,635	$ 19,397	$ 284
Ending Balance, shares at Mar. 31, 2018		21,214,662

Consolidated Statements of Cash

Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities
Net income	$ 10,758	$ 5,932
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,993	3,204
Loss on rental units and other fixed assets	284	325
Gain on sale of former rental assets	(401)	(37)
Provision for sales returns and doubtful accounts	4,920	3,181
Provision for rental revenue adjustments	719	1,731
Provision for inventory obsolescence and other inventory losses	73	7
Stock-based compensation expense	3,381	1,891
Deferred income taxes	(1,798)	(54)
Changes in operating assets and liabilities:
Accounts receivable	(9,206)	(5,015)
Inventories	(4,327)	49
Deferred cost of revenue	26	16
Income tax receivable	726	(129)
Prepaid expenses and other current assets	(1,192)	(773)
Accounts payable and accrued expenses	3,928	4,045
Accrued payroll	(274)	(2,291)
Warranty reserve	1,074	528
Deferred revenue	608	621
Income tax payable	(36)
Other noncurrent liabilities	(16)	(19)
Net cash provided by operating activities	12,240	13,212
Cash flows from investing activities
Purchases of available-for-sale investments	(11,565)	(9,988)
Maturities of available-for-sale investments	8,525	7,950
Investment in property and equipment	(2,075)	(593)
Production and purchase of rental equipment	(1,447)	(1,188)
Proceeds from sale of former assets	573	54
Net cash used in investing activities	(5,989)	(3,765)
Cash flows from financing activities
Proceeds from stock options exercised	4,459	2,222
Proceeds from employee stock purchases	988	581
Payment of employment taxes related to release of restricted stock	(302)
Net cash provided by financing activities	5,145	2,803
Effect of exchange rates on cash	(65)	4
Net increase in cash and cash equivalents	11,331	12,254
Cash and cash equivalents, beginning of period	142,953	92,851
Cash and cash equivalents, end of period	154,284	105,105
Supplemental disclosures of cash flow information
Cash paid (received) during the period for income taxes, net of refunds received	(14)	$ 45
Supplemental disclosure of non-cash transactions
Property and equipment in accounts payable and accrued liabilities	$ 93

Business Overview

Business Overview	3 Months Ended
	Mar. 31, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Business Overview	1. Business overview Inogen, Inc. (Company or Inogen) was incorporated in Delaware on November 27, 2001. The Company is a medical technology company that primarily develops, manufactures and markets innovative portable oxygen concentrators used to deliver supplemental long-term oxygen therapy to patients suffering from chronic respiratory conditions. Traditionally, these patients have relied on stationary oxygen concentrator systems for use in the home and oxygen tanks or cylinders for mobile use, which the Company calls the delivery model. The tanks and cylinders must be delivered regularly and have a finite amount of oxygen, which requires patients to plan activities outside of their homes around delivery schedules and a finite oxygen supply. Additionally, patients must attach long, cumbersome tubing to their stationary concentrators simply to enable mobility within their homes. The Company’s proprietary Inogen One ® ® ® ® Portable oxygen concentrators represented the fastest-growing segment of the Medicare oxygen therapy market between 2012 and 2016. The Company estimates based on 2016 Medicare data that the number of patients using portable oxygen concentrators represents approximately 9.1% of the total addressable oxygen market in the United States, although the Medicare data does not account for private insurance and cash-pay patients in the market. Based on 2016 industry data, the Company believes it was the leading worldwide manufacturer of portable oxygen concentrators. The Company believes it is the only manufacturer of portable oxygen concentrators that employs a direct-to-consumer strategy in the United States, meaning the Company markets its products to patients, processes their physician paperwork, provides clinical support as needed and bills Medicare or insurance on their behalf. To pursue a direct-to-consumer strategy, the Company’s manufacturing competitors would need to meet national accreditation and state-by-state licensing requirements and secure Medicare billing privileges including Medicare competitive bidding contracts, as well as compete with the home medical equipment providers who many of the Company’s manufacturing competitors sell to across their entire homecare business. Since adopting the Company’s direct-to-consumer strategy in 2009, the Company has directly sold or rented more than 409,000 of its Inogen oxygen concentrators as of March 31, 2018. The Company incorporated Inogen Europe Holding B.V., a Dutch limited liability company, on April 13, 2017. The Company owns all outstanding stock of Inogen Europe Holding B.V., which became a wholly owned subsidiary of the Company. On May 4, 2017, the Company, through its wholly owned subsidiary, Inogen Europe Holding B.V., acquired all issued and outstanding capital stock of MedSupport Systems B.V. (MedSupport).

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	2. Basis of presentation and summary of significant accounting policies The accompanying consolidated financial statements are unaudited. The consolidated balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements of the Company. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (U.S. GAAP) for interim financial information, and in management’s opinion, includes all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position, its results of operations, stockholders’ equity and cash flows for the interim periods presented. The results of operations for the three months ended March 31, 2018 are not necessarily indicative of the results to be expected for the full fiscal year or any other period. The accompanying consolidated financial statements should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 27, 2018. There have been no significant changes in the Company’s accounting policies from those disclosed in its Annual Report on Form 10-K filed with the SEC on February 27, 2018. Basis of consolidation The consolidated financial statements include the accounts of Inogen, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated. Use of estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases these estimates and assumptions upon historical experience, existing and known circumstances, authoritative accounting pronouncements and other factors that management believes to be reasonable. Significant areas requiring the use of management estimates relate to revenue recognition and determining the stand-alone selling price (SSP) of performance obligations, inventory and rental asset valuations and write-downs, accounts receivable allowances for bad debts, returns and adjustments, warranty expense, stock compensation expense, depreciation and amortization, income tax provision and uncertain tax positions, fair value of financial instruments, and fair value of acquired intangible assets and goodwill. Actual results could differ from these estimates. Revenue The Company generates revenue primarily from sales and rentals of its products. The Company’s products consist of its proprietary line of oxygen concentrators and related accessories. Other revenue, which is included in sales revenue on the Consolidated Statements of Comprehensive Income, consists of repair services and freight revenue for product shipments. Sales revenue Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services. Revenue from product sales is generally recognized upon shipment of the product but is deferred for certain transactions when control has not yet transferred to the customer. The Company’s product is generally sold with a right of return and the Company may provide other incentives, which are accounted for as variable consideration when estimating the amount of revenue to recognize. Returns and incentives are estimated at the time sales revenue is recognized. The provisions for estimated returns are made based on known claims and estimates of additional returns based on historical data and future expectations. Sales revenue incentives within the Company’s contracts are estimated based on the most likely amounts expected on the related sales transaction and recorded as a reduction to revenue at the time of sale in accordance with the terms of the contract. The Company also offers a lifetime warranty for direct-to-consumer sales of its portable concentrators. For a fixed price, the Company agrees to provide a fully functional portable oxygen concentrator for the remaining life of the patient. Lifetime warranties are only offered to patients upon the initial sale of portable oxygen concentrators by the Company and are non-transferable. Lifetime warranties are considered to be a distinct performance obligation that are accounted for separately from its sale of portable oxygen concentrators with a standard warranty of three years . The revenue is allocated to the distinct lifetime warranty performance obligation based on a relative SSP method. The Company has vendor-specific objective evidence of the selling price for its equipment. To determine the selling price of the lifetime warranty, the Company uses its best estimate of the SSP for the distinct performance obligation as the lifetime warranty is neither separately priced nor is the selling price available through third-party evidence. To calculate the selling price associated with the lifetime warranties, management considered the profit margins of the overall business, the average estimated cost of lifetime warranties and the price of extended warranties. Revenue from the distinct lifetime warranty is deferred after the delivery of the equipment for three years and recognized on a straight-line basis during the fourth and fifth year, which is the estimated usage period of the contract based on the average patient life expectancy. Revenue from the sale of the Company’s repair services is recognized when the performance obligations are satisfied and collection of the receivables is probable. Other revenue from sale of replacement parts and non-warranty repair services is generally recognized when product is shipped to customers. Freight revenue consists of fees associated with the deployment of products internationally and domestically when expedited freight options are requested or when minimum order quantities are not met. Freight revenue is generally recognized upon shipment of the product but is deferred if control has not yet transferred to the customer. Shipping and handling costs for sold products and rental assets shipped to the Company’s customers are included on the Consolidated Statements of Comprehensive Income as part of cost of sales revenue and cost of rental revenue, respectively. The payment terms and conditions of customer contracts vary by customer type and the products and services offered. For certain products or services and customer types, the Company requires payment before the products or services are delivered to the customer. The timing of sales revenue recognition, billing and cash collection results in billed accounts receivable and deferred revenue in the consolidated balance sheet. Contract liabilities primarily consist of deferred revenue related to lifetime warranties on direct-to-consumer sales revenue when cash payments are received in advance of services performed under the contract. The contract with the customer states the final terms of the sale, including the description, quantity, and price of each product or service purchase. The increase in deferred revenue related to lifetime warranties for the three months ended March 31, 2018 is primarily driven by $1,459 of cash payments received in advance of satisfying the . The Company elected to apply the practical expedient in accordance with ASC 606 and did not evaluate contracts of one year or less for the existence of a significant financing component The Company’s sales revenue is primarily derived from the sale of its Inogen One systems, Inogen At Home systems, and related accessories to individual consumers, HME providers, distributors, the Company’s private label partner and resellers worldwide. Sales revenue is classified into two areas: business-to-business sales and direct-to-consumer sales. The following table sets forth the Company’s sales revenue disaggregated by sales channel and geographic region: Three months ended March 31, Revenue by region and category 2018 2017 Business-to-business domestic sales $ 28,016 $ 17,461 Business-to-business international sales 16,906 11,423 Direct-to-consumer domestic sales 28,662 17,082 Total sales revenue $ 73,584 $ 45,966 Rental revenue The Company recognizes equipment rental revenue over the non-cancelable lease term, which is one month, less estimated adjustments, in accordance with Accounting Standards Codification (ASC) — Leases The lease term begins on the date products are shipped to patients and are recorded at amounts estimated to be received under reimbursement arrangements with third-party payors, including Medicare, private payors, and Medicaid. Due to the nature of the industry and the reimbursement environment in which the Company operates, certain estimates are required to record net revenue and accounts receivable at their net realizable values. Inherent in these estimates is the risk that they will have to be revised or updated as additional information becomes available. Specifically, the complexity of many third-party billing arrangements and the uncertainty of reimbursement amounts for certain services from certain payors may result in adjustments to amounts originally recorded. Such adjustments are typically identified and recorded at the point of cash application, claim denial or account review. The Company adjusts revenue for historical trends on revenue adjustments due to timely filings, deaths, hospice, and other types of analyzable adjustments on a monthly basis. Accounts receivable are reduced by an allowance for doubtful accounts which provides for those accounts from which payment is not expected to be received although product was delivered, and revenue was earned. The determination that an account is uncollectible, and the ultimate write-off of that account occurs once collection is considered to be not probable, and it is written-off and charged to the allowance at that time. Amounts billed but not earned due to the timing of the billing cycle are deferred and recognized in rental revenue on a straight-line basis over the monthly billing period. For example, if the first day of the billing period does not fall on the first of the month, then a portion of the monthly billing period will fall in the subsequent month and the related revenue and cost would be deferred based on the service days in the following month. Rental revenue is recognized as upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services, less estimated adjustments. Revenue not billed at the end of the period is reviewed for the probability of collection and accrued if collection is probable. Rental revenue is not guaranteed, and payment will cease if the patient no longer needs oxygen or returns the equipment. Rental revenue is recognized at estimated allowable amounts that reflect the full consideration the Company expects to receive in exchange for the equipment; transfers to secondary insurances or patient responsibility have no net effect on revenue. Rental revenue is earned for that entire month if the patient is on service on the first day of the 30-day period commencing on the recurring date of service for a particular claim, regardless if there is a change in condition or death after that date. Included in rental revenue are unbilled amounts for which the revenue recognition criteria had been met as of period-end but were not yet billed to the payor. The estimate of net unbilled rental revenue recognized is based on historical trends and estimates of future collectability. In addition, the Company estimates potential future adjustments and write-offs of these unbilled amounts and includes these estimates in the allowance for adjustments and write-offs of rental revenue which is netted against gross receivables. Recently issued accounting pronouncements not yet adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Land Easement Practice Expedient for Transition to Topic 842 In June 2016, the FASB issued ASU No. 2016-13, Accounting for Credit Losses (Topic 326) In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging In January 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income Recently adopted accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue with Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net) In January 2017, the FASB issued ASU No. 2017-01, Clarifying the Definition of a Business Business segments The Company operates and reports in only one operating and reportable segment – development, manufacturing, marketing, sales, and rental of respiratory products. Management reports financial information on a consolidated basis to the Company’s chief operating decision maker.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	3. Fair value of financial instruments The Company’s financial instruments consist of cash and cash equivalents, marketable securities, accounts receivable, accounts payable and accrued expenses. The carrying values of its financial instruments approximate fair value based on their short-term nature. Fair value accounting Accounting Standards Codification (ASC) 820 — Fair Value Measurements and Disclosures Level input Input definition Level 1 Inputs are unadjusted, quoted prices for identical assets or liabilities in active markets at the measurement date. Level 2 Inputs, other than quoted prices included in Level 1 that are observable for the asset or liability through corroboration with market data at the measurement date. Level 3 Unobservable inputs that reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. The Company obtained the fair value of its available-for-sale investments, which are not in active markets, from a third-party professional pricing service using quoted market prices for identical or comparable instruments, rather than direct observations of quoted prices in active markets. The Company's professional pricing service gathers observable inputs for all of its fixed income securities from a variety of industry data providers (e.g., large custodial institutions) and other third-party sources. Once the observable inputs are gathered, all data points are considered, and the fair value is determined. The Company validates the quoted market prices provided by its primary pricing service by comparing their assessment of the fair values against the fair values provided by its investment managers. The Company's investment managers use similar techniques to its professional pricing service to derive pricing as described above. As all significant inputs were observable, derived from observable information in the marketplace or supported by observable levels at which transactions are executed in the marketplace, the Company has classified its available-for-sale investments within Level 2 of the fair value hierarchy. The following table summarizes fair value measurements by level for the assets measured at fair value on a recurring basis for cash, cash equivalents and marketable securities: As of March 31, 2018 Gross Cash Adjusted unrealized and cash Marketable cost losses Fair value equivalents securities Cash $ 43,188 $ — $ 43,188 $ 43,188 $ — Level 1: Money market accounts 107,906 — 107,906 107,906 — Level 2: Certificates of deposit 11,652 (1 ) 11,651 3,190 8,461 Corporate bonds 22,086 (43 ) 22,043 — 22,043 Agency mortgage-backed securities 1,005 — 1,005 — 1,005 U.S. Treasury securities 2,503 — 2,503 — 2,503 Total $ 188,340 $ (44 ) $ 188,296 $ 154,284 $ 34,012 As of December 31, 2017 Gross Cash Adjusted unrealized and cash Marketable cost losses Fair value equivalents securities Cash $ 46,237 $ — $ 46,237 $ 46,237 $ — Level 1: Money market accounts 93,430 — 93,430 93,430 — Level 2: Certificates of deposit 11,010 (4 ) 11,006 490 10,516 Corporate bonds 20,789 (21 ) 20,768 2,796 17,972 Agency mortgage-backed securities 2,005 (1 ) 2,004 — 2,004 U.S. Treasury securities 499 — 499 — 499 Total $ 173,970 $ (26 ) $ 173,944 $ 142,953 $ 30,991 The following table summarizes the estimated fair value of the Company’s investments in marketable securities, accounted for as available-for-sale securities and classified by the contractual maturity date of the securities: March 31, 2018 Due within one year $ 34,012 Derivative instruments and hedging activities The Company transacts business in foreign currencies and has international sales and expenses denominated in foreign currencies, subjecting the Company to foreign currency risk. The Company has entered into foreign currency forward contracts, generally with maturities of twelve months or less, to reduce the volatility of cash flows primarily related to forecasted revenue denominated in certain foreign currencies. These contracts allow the Company to sell Euros in exchange for U.S. dollars at specified contract rates. Forward contracts are used to hedge forecasted sales over specific months. Changes in the fair value of these forward contracts designed as cash flow hedges are recorded as a component of accumulated other comprehensive income (loss) within stockholders’ equity and are recognized in the consolidated statements of comprehensive income during the period which approximates the time the corresponding sales occur. The Company may also enter into foreign exchange contracts that are not designated as hedging instruments for financial accounting purposes. These contracts are generally entered into to offset the gains and losses on certain asset and liability balances until the expected time of repayment. Accordingly, any gains or losses resulting from changes in the fair value of the non-designated contracts are reported in other expense, net in the consolidated statements of comprehensive income. The gains and losses on these contracts generally offset the gains and losses associated with the underlying foreign currency-denominated balances, which are also reported in other income (expense), net. The Company records the assets or liabilities associated with derivative instruments and hedging activities at fair value based on Level 2 inputs in other current assets or other current liabilities, respectively, in the consolidated balance sheet. The Company had a related payable of $255 and $66 as of March 31, 2018 and December 31, 2017, respectively. The Company classifies the foreign currency derivative instruments within Level 2 in the fair value hierarchy as the valuation inputs are based on quoted prices and market observable data of whether it is designated and qualifies for hedge accounting. The Company documents the hedging relationship and its risk management objective and strategy for undertaking the hedge, the hedging instrument, the hedged transaction, the nature of the risk being hedged, how the hedging instrument’s effectiveness in offsetting the hedged risk will be assessed prospectively and retrospectively, and a description of the method used to measure ineffectiveness. The Company assesses hedge effectiveness and ineffectiveness at a minimum quarterly but may assess it monthly. For derivative instruments that are designed and qualify as part of a cash flow hedging relationship, the effective portion of the gain or loss on the derivative is reported in other comprehensive income (loss) and reclassified into earnings in the same periods during which the hedged transaction affects earnings. Gains and losses on the derivative representing either hedge ineffectiveness or hedge components excluded from the assessment of effectiveness are recognized in current period earnings. The Company will discontinue hedge accounting prospectively when it determines that the derivative is no longer effective in offsetting cash flows attributable to the hedge risk. The cash flow hedge is de-designated because a forecasted transaction is not probable of occurring, or management determines to remove the designation of the cash flow hedge. In all situations in which hedge accounting is discontinued and the derivative remains outstanding, the Company continues to carry the derivative at its fair value on the balance sheet and recognizes any subsequent changes in the fair value in earnings. When it is probable that a forecasted transaction will not occur, the Company will discontinue hedge accounting and recognize immediately in earnings gains and losses that were accumulated in other comprehensive income (loss) related to the hedging relationship. Accumulated other comprehensive income (loss) The components of accumulated other comprehensive income (loss) were as follows: Foreign Unrealized Unrealized Accumulated currency losses on losses other translation available-for- on cash comprehensive adjustments sale investments flow hedges income Balance as of December 31, 2017 $ 363 $ (17 ) $ (74 ) $ 272 Other comprehensive gain (loss) 108 (19 ) (77 ) 12 Balance as of March 31, 2018 $ 471 $ (36 ) $ (151 ) $ 284 Comprehensive income (loss) is the total net earnings and all other non-owner changes in equity. Except for net income and unrealized gains and losses on cash flow hedges and available-for-sale investments, the Company does not have any transactions or other economic events that qualify as comprehensive income (loss).

Balance Sheet Components

Balance Sheet Components	3 Months Ended
	Mar. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Components	4. Balance sheet components Cash, cash equivalents and marketable securities The Company considers all short-term highly liquid investments with a maturity of three months or less to be cash equivalents. Cash equivalents are recorded at cost plus accrued interest, which is considered adjusted cost, and approximates fair value. Certificates of deposit and agency mortgage-backed securities are included in cash equivalents and marketable securities based on the maturity date of the security. Short-term investments are included in marketable securities in the current period presentation. The Company considers investments with maturities greater than three months, but less than one year, to be marketable securities. Investments are classified as available-for-sale and are reported at fair value with unrealized gains or losses, if any, reported, net of tax, in accumulated other comprehensive income (loss). All income generated and realized gains or losses from investments are recorded to other income (expense). The Company reviews its investments to identify and evaluate investments that have an indication of possible impairment. Factors considered in determining whether a loss is temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company's intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. Credit losses and other-than-temporary impairments are declines in fair value that are not expected to recover and are charged to other income (expense), net. March 31, December 31, Cash and cash equivalents 2018 2017 Cash $ 43,188 $ 46,237 Money market accounts 107,906 93,430 Certificates of deposit 3,190 490 Corporate bonds — 2,796 Total cash and cash equivalents $ 154,284 $ 142,953 Marketable securities Certificates of deposit $ 8,461 $ 10,516 Corporate bonds 22,043 17,972 Agency mortgage-backed securities 1,005 2,004 U.S. Treasury securities 2,503 499 Total marketable securities $ 34,012 $ 30,991 Accounts receivable and allowance for bad debts, returns, and adjustments Accounts receivable are customer obligations due under normal sales and rental terms. The Company performs credit evaluations of the customers’ financial condition and generally does not require collateral. The allowance for doubtful accounts is maintained at a level that, in management’s opinion, is adequate to absorb potential losses related to accounts receivable and is based upon the Company’s continuous evaluation of the collectability of outstanding balances. Management’s evaluation takes into consideration such factors as past bad debt experience, economic conditions and information about specific receivables. The Company’s evaluation also considers the age and composition of the outstanding amounts in determining their net realizable value. The allowance for doubtful accounts is based on estimates, and ultimate losses may vary from current estimates. As adjustments to these estimates become necessary, they are reported in earnings in the periods in which they become known. This allowance is increased by bad debt provisions charged to bad debt expense, net of recoveries, in operating expense and is reduced by direct write-offs. The Company generally does not allow returns from providers for reasons not covered under its standard warranty. Therefore, provision for sales returns applies primarily to direct-to-consumer sales. This reserve is calculated based on actual historical return rates under the Company’s 30-day return program and is applied to the related sales revenue for the last month of the quarter reported. The Company also records an allowance for rental revenue adjustments which is recorded as a reduction of rental revenue and net rental accounts receivable balances. These adjustments result from contractual adjustments, audit adjustments, untimely claims filings, or billings not paid due to another provider performing same or similar functions for the patient in the same period, all of which prevent billed revenue from becoming realizable. The allowance is based on historical revenue adjustments as a percentage of rental revenue billed and unbilled during the related period. When recording the allowance for doubtful accounts, the bad debt expense account (general and administrative expense account) is charged; when recording allowance for sales returns, the sales returns account (contra sales revenue account) is charged; and when recording the allowance for rental reserve adjustments, the rental revenue adjustments account (contra rental revenue account) is charged. As of March 31, 2018 and December 31, 2017, included in accounts receivable on the consolidated balance sheets were earned but unbilled receivables of $1,299 and $1,470, respectively. These balances reflect gross unbilled receivables prior to any allowances for adjustments and write-offs. The Company consistently applies its allowance estimation methodology from period-to-period. The Company’s best estimate is made on an accrual basis and adjusted in future periods as required. Any adjustments to the prior period estimates are included in the current period. As additional information becomes known, the Company adjusts its assumptions accordingly to change its estimate of the allowance. Gross accounts receivable balance concentrations by major category as of March 31, 2018 and December 31, 2017 were as follows: March 31, December 31, Gross accounts receivable 2018 2017 Rental (1) $ 6,143 $ 6,236 Business-to-business & other receivables (2) 32,945 28,474 Total gross accounts receivable $ 39,088 $ 34,710 Net accounts receivable (gross accounts receivable, net of allowances) balance concentrations by major category as of March 31, 2018 and December 31, 2017 were as follows: March 31, December 31, Net accounts receivable 2018 2017 Rental (1) $ 3,695 $ 4,212 Business-to-business & other receivables (2) 31,394 27,232 Total net accounts receivable $ 35,089 $ 31,444 (1) Rental includes Medicare, Medicaid/other government, private insurance and patient pay. (2) Business-to-business receivables included one customer with a gross accounts receivable balance of $9,461 and $10,394 as of March 31, 2018 and December 31, 2017, respectively. This customer received extended payment terms through a direct financing plan offered. The Company also has a credit insurance policy in place, which allocated up to $18,000 in coverage as of March 31, 2018 and allocated up to $12,000 in coverage as of December 31, 2017 for this customer with a $1,000 deductible and 10% retention. The following tables set forth the accounts receivable allowances as of March 31, 2018 and December 31, 2017: March 31, December 31, Allowances - accounts receivable 2018 2017 Doubtful accounts $ 1,589 $ 1,415 Rental revenue adjustments 1,013 947 Sales returns 1,397 904 Total allowances - accounts receivable $ 3,999 $ 3,266 Concentration of credit risk Financial instruments that potentially subject the Company to concentration of credit risk consist principally of cash, cash equivalents, marketable securities and accounts receivable. At times, cash account balances may be in excess of the amounts insured by the Federal Deposit Insurance Corporation (FDIC). However, management believes the risk of loss to be minimal. The Company performs periodic evaluations of the relative credit standing of these institutions and has not experienced any losses on its cash and cash equivalents to date. The Company has entered into hedging relationships with a single counterparty to offset the forecasted Euro-based revenues. The credit risk has been reduced due to a net settlement arrangement whereby the Company is allowed to net settle transactions with a single net amount payable by one party to the other. Concentration of customers and vendors The Company primarily sells its products to traditional home medical equipment providers, distributors, and resellers in the United States and in foreign countries on a credit basis. The Company also sells its products direct-to-consumers on a primarily prepayment basis. One single customer represented more than 10% of the Company’s total revenue for the three months ended March 31, 2018 and March 31, 2017. Two customers with accounts receivable balances of $9,461 and $8,077, respectively, each represented more than 10% of the Company’s net accounts receivable balance as of March 31, 2018, and two customers with accounts receivable balances of $10,394 and $6,459, respectively, each represented more than 10% of the Company’s net accounts receivable balance as of December 31, 2017. The Company currently purchases raw materials from a limited number of vendors, which resulted in a concentration of three major vendors. The three major vendors supply the Company with raw materials used to manufacture the Company’s products. For the three months ended March 31, 2018, the Company’s three major vendors accounted for 18.5%, 15.1%, and 12.0%, respectively, of total raw material purchases. For the three months ended March 31, 2017, the Company’s three major vendors accounted for 18.8%, 11.6% and 10.9%, respectively, of total raw material purchases. A portion of revenue is earned from sales outside the United States. Approximately 76.9% and 72.2% of the non-U.S. revenue for the three months ended March 31, 2018 and March 31, 2017, respectively, were invoiced in Euros. A breakdown of the Company’s revenue from U.S. and non-U.S. sources for the three months ended March 31, 2018 and March 31, 2017 is as follows: Three months ended March 31, 2018 2017 U.S. revenue $ 62,145 $ 41,077 Non-U.S. revenue 16,906 11,423 Total revenue $ 79,051 $ 52,500 Inventories Inventories are stated at the lower of cost and net realizable value. Cost is determined using a standard cost method, including material, labor and manufacturing overhead, whereby the standard costs are updated at least quarterly to reflect approximate actual costs using the first-in, first-out (FIFO) method. The Company records adjustments at least quarterly to inventory for potentially excess, obsolete, slow-moving or impaired items. The Company recorded noncurrent inventory related to inventories that are expected to be realized or consumed after one year of $452 and $644 as of March 31, 2018 and December 31, 2017, respectively. Noncurrent inventories are primarily related to raw materials purchased in bulk to support long-term expected repairs to reduce costs and are classified in other assets. Inventories that are considered current consist of the following: March 31, December 31, 2018 2017 Raw materials and work-in-progress $ 18,814 $ 16,324 Finished goods 4,640 2,917 Less: reserves (489 ) (399 ) Inventories $ 22,965 $ 18,842 Property and equipment Property and equipment are stated at cost. Depreciation and amortization are calculated using the straight-line method over the assets’ estimated useful lives as follows: Rental equipment 1.5-5 years Manufacturing equipment and tooling 2-5 years Computer equipment and software 2-3 years Furniture and equipment 3-5 years Leasehold improvements Lesser of estimated useful life or remaining lease term Expenditures for additions, improvements and replacements are capitalized and depreciated to a salvage value of $0. Repair and maintenance costs on rental equipment are included in cost of rental revenue on the consolidated statements of comprehensive income. Repair and maintenance expense, which includes labor, parts and freight, for rental equipment was $560 and $651 for the three months ended March 31, 2018 and March 31, 2017, respectively. Included within property and equipment is construction in process, primarily related to the design and engineering of tooling, jigs and other machinery. In addition, this item also includes computer software or development costs that have been purchased but have not completed the final configuration process for implementation into the Company’s systems. These items have not been placed in service; therefore, no depreciation or amortization was recognized for these items in the respective periods. Depreciation and amortization expense related to rental equipment and other property and equipment are summarized below for the three months ended March 31, 2018 and March 31, 2017, respectively. Three months ended March 31, 2018 2017 Rental equipment $ 2,165 $ 2,689 Other property and equipment 530 488 Total depreciation and amortization $ 2,695 $ 3,177 Property and equipment and rental equipment with associated accumulated depreciation are summarized below for March 31, 2018 and December 31, 2017, respectively. March 31, December 31, Property and equipment 2018 2017 Rental equipment, net of allowances of $754 and $754, respectively $ 47,420 $ 49,349 Other property and equipment 17,387 15,219 Property and equipment 64,807 64,568 Accumulated depreciation Rental equipment 33,671 34,754 Other property and equipment 10,238 9,711 Accumulated depreciation 43,909 44,465 Property and equipment, net Rental equipment, net of allowances of $754 and $754, respectively 13,749 14,595 Other property and equipment 7,149 5,508 Property and equipment, net $ 20,898 $ 20,103 Long-lived assets The Company accounts for the impairment and disposition of long-lived assets in accordance with ASC 360 — Property, Plant, and Equipment Goodwill The changes in the carrying amount of goodwill for the three months ended March 31, 2018 were as follows: Balance as of December 31, 2017 $ 2,363 Translation adjustment 67 Balance as of March 31, 2018 $ 2,430 Intangible assets There were no impairments recorded related to the Company’s intangible assets during the three months ended March 31, 2018 and March 31, 2017. Amortization expense for intangible assets for the three months ended March 31, 2018 and March 31, 2017 was $298 and $27, respectively. The following tables represent the net carrying values of intangible assets as of the respective dates: Average estimated Gross useful lives carrying Accumulated March 31, 2018 (in years) amount amortization Net amount Licenses 10 $ 185 $ 142 $ 43 Patents and websites 5 4,173 1,131 3,042 Customer relationships 4 1,479 339 1,140 Non-compete agreement 3 246 75 171 Commercials 2-3 303 243 60 Total $ 6,386 $ 1,930 $ 4,456 Average estimated Gross useful lives carrying Accumulated December 31, 2017 (in years) amount amortization Net amount Licenses 10 $ 185 $ 137 $ 48 Patents and websites 5 4,173 959 3,214 Customer relationships 4 1,437 240 1,197 Non-compete agreement 3 240 52 188 Commercials 2-3 303 233 70 Total $ 6,338 $ 1,621 $ 4,717 Annual estimated amortization expense for intangibles for each of the succeeding fiscal years is summarized as follows: March 31, 2018 Remaining 9 months of 2018 $ 906 2019 1,147 2020 1,069 2021 790 2022 544 Thereafter — $ 4,456 Current liabilities Accounts payable and accrued expenses as of March 31, 2018 and December 31, 2017 consisted of the following: March 31, December 31, 2018 2017 Accounts payable $ 13,589 $ 9,541 Accrued inventory (in-transit and unvouchered receipts) and trade payables 7,644 7,252 Accrued purchasing card liability 2,089 2,381 Accrued franchise, sales and use taxes 498 479 Other accrued expenses 940 973 Accounts payable and accrued expenses $ 24,760 $ 20,626 Accrued payroll as of March 31, 2018 and December 31, 2017 consisted of the following: March 31, December 31, 2018 2017 Accrued bonuses $ 1,306 $ 3,086 Accrued wages and other payroll related items 3,803 2,453 Accrued vacation 1,498 1,338 Accrued payroll $ 6,607 $ 6,877

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings per Share	5. Earnings per share Earnings per share (EPS) is computed in accordance with ASC 260 —Earnings per Share Basic earnings per share is calculated using the Company’s weighted-average outstanding common shares. Diluted earnings per share is calculated using the Company’s weighted-average outstanding common shares including the dilutive effect of stock awards as determined under the treasury stock method. The computation of EPS is as follows: Three months ended March 31, 2018 2017 Numerator—basic and diluted: Net income $ 10,758 $ 5,932 Denominator: Weighted-average common shares - basic common stock (1) 21,026,154 20,489,532 Weighted-average common shares - diluted common stock 22,295,213 21,579,721 Net income per share - basic common stock $ 0.51 $ 0.29 Net income per share - diluted common stock $ 0.48 $ 0.27 Denominator calculation from basic to diluted: Weighted-average common shares - basic common stock (1) 21,026,154 20,489,532 Stock options and other dilutive awards 1,269,059 1,090,189 Weighted-average common shares - diluted common stock 22,295,213 21,579,721 Shares excluded from diluted weighted-average shares: Stock options — 25,700 Restricted stock units and restricted stock awards 75,926 — Shares excluded from diluted weighted-average shares 75,926 25,700 (1) Unvested restricted stock units and restricted stock awards are not included as shares outstanding in the calculation of basic earnings per share. Vested restricted stock units and restricted stock awards are included in basic earnings per share if all vesting and performance criteria have been met. Performance-based restricted stock units and restricted stock awards are included in the number of shares used to calculate diluted earnings per share as long as all applicable performance criteria are met, and their effect is dilutive. Restricted stock awards are eligible to receive all dividends declared on the Company’s common shares during the vesting period; however, such dividends are not paid until the restrictions lapse. The computations of diluted net income attributable to common stockholders exclude common stock options, restricted stock units and restricted stock awards, which were anti-dilutive for the three months ended March 31, 2018 and March 31, 2017, respectively.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	6. Income taxes The Company accounts for income taxes in accordance with ASC 740 —Income Taxes The Company accounts for uncertainties in income tax in accordance with ASC 740-10 —Accounting for Uncertainty in Income Taxes The Company recognizes interest and penalties on taxes, if any, within its income tax provision on its consolidated statements of comprehensive income. No significant interest or penalties were recognized during the periods presented. On December 22, 2017, Tax Cuts and Jobs Act (TCJA) was enacted into law, which significantly changes existing U.S. tax law and includes numerous provisions that affect the Company’s business. Changes include, but are not limited to, a corporate tax rate decrease from 34% to 21% effective for tax years beginning after December 31, 2017, expensing of capital expenditures, the transition of U.S. international taxation from a worldwide tax system to a territorial system, a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings, and limitations on the deductibility of certain executive compensation and other deductions As of March 31, 2018, the Company has not completed the accounting for the income tax effects of the TCJA. No further changes have been made to the provisional amounts reported for the transition tax or the remeasurement of the deferred taxes during the three months ended March 31, 2018. For the foreign derived intangible income, executive compensation, and other deductions, the Company recorded an estimate in the effective tax rate for the three months ended March 31, 2018. The Company has not yet determined a policy election with respect to whether to record deferred taxes for basis differences expected to reverse as a result of the global intangible low tax income provisions in future periods or use the period cost method. Given the significant complexity of the TCJA, the Company will continue to evaluate and analyze the impact of this legislation. New guidance from regulators, interpretation of the law, and refinement of the Company’s estimates from ongoing analysis of data and tax positions may change the provisional amounts. The Company has operations in the U.S., multiple U.S. states and the Netherlands. The statute of limitations has expired for all tax years prior to 2013 for federal jurisdictions and the Netherlands, and 2012 to 2013 for various state tax jurisdictions. However, the net operating loss generated on the Company’s federal and state tax returns in prior years may be subject to adjustments by the federal and state tax authorities. The Company determined the income tax provision for interim periods using an estimate of the Company’s annual effective tax rate, adjusted for discrete items arising in that quarter. In each quarter, the Company updates its estimated annual effective tax rate, and if the estimated annual effective

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Stockholders' Equity	7. Stockholders’ equity The Company has a 2002 Stock Incentive Plan (2002 Plan) as amended, under which the Company granted options to purchase shares of its common stock. As of March 31, 2018, options to purchase 40,508 shares of common stock remained outstanding under the 2002 Plan. The 2002 Plan was terminated in March 2012 in connection with the adoption of the 2012 Plan, and, accordingly, no new options are available for issuance under this plan. The 2002 Plan continues to govern outstanding awards granted thereunder. The Company has a 2012 Equity Incentive Plan (2012 Plan) under which the Company granted options to purchase shares of its common stock. As of March 31, 2018, options to purchase 306,266 shares of common stock remained outstanding under the 2012 Plan. The 2012 Plan was terminated in connection with the Company’s initial public offering in February 2014, and accordingly, no new options are available for issuance under this plan. The 2012 Plan continues to govern outstanding awards granted thereunder. The Company has a 2014 Equity Incentive Plan (2014 Plan) that provides for the grant of incentive stock options, within the meaning of Section 422 of the Internal Revenue Code, to the Company’s employees and any parent and subsidiary corporation’s employees, and for the grant of nonstatutory stock options, restricted stock, restricted stock units, restricted stock awards, stock appreciation rights, performance units and performance shares to its employees, directors and consultants and its parent and subsidiary corporations’ employees and consultants. As of March 31, 2018, awards with respect to 1,476,190 shares of the Company’s common stock were outstanding, and 1,920,713 shares of common stock remained available for issuance under the 2014 Plan. The shares available for issuance under the 2014 Plan will be increased by any shares returned to the 2002 Plan, 2012 Plan and the 2014 Plan as a result of expiration or termination of awards (provided that the maximum number of shares that may be added to the 2014 Plan pursuant to such previously granted awards under the 2002 Plan and 2012 Plan is 2,328,569 shares). The number of shares available for issuance under the 2014 Plan also is increased annually on the first day of each fiscal year by an amount equal to the least of: • 895,346 shares; • 4% of the outstanding shares of common stock as of the last day of the Company’s immediately preceding fiscal year; or • such other amount as the Company’s board of directors may determine. For 2018, an additional 839,054 shares were added to the 2014 Plan share reserve pursuant to the provision described above. Stock options Options typically expire between seven and ten years from the date of grant and vest over one to four year terms. Options have been granted to employees, directors and consultants of the Company, as determined by the board of directors, at the deemed fair market value of the shares underlying the options at the date of grant. The activity for stock options under the Company’s stock plans is as follows: Remaining weighted- Weighted- average Per share average contractual average Price per exercise terms intrinsic Options share price (in years) value Outstanding as of December 31, 2017 1,836,426 $0.60-$83.30 $ 30.77 4.58 $ 88.31 Granted — — — Exercised (169,594 ) 0.60-58.95 26.29 Forfeited — — — Expired — — — Outstanding as of March 31, 2018 1,666,832 $0.60-$83.30 $ 31.23 4.45 $ 91.61 Vested and exercisable as of March 31, 2018 1,134,940 $0.60-$83.30 $ 25.82 4.31 $ 97.02 Vested and expected to vest as of March 31, 2018 1,631,773 $0.60-$83.30 $ 30.98 4.44 $ 91.86 The unrecognized compensation expense related to non-vested stock-based compensation granted under the Plans as of March 31, 2018 and March 31, 2017 was $7,866 and $13,511, respectively. S tock incentive awards The Company grants restricted stock units (RSUs) and restricted stock awards (RSAs) under the 2014 Plan (Stock Awards). The Stock Awards vest either based solely on the satisfaction of time-based service conditions or on the satisfaction of time-based service conditions combined with performance criteria. Stock Awards are subject to forfeiture if the holder’s services to the Company terminate before vesting. Stock Awards granted with only time-based service vesting conditions generally vest over a four-year service period, as defined in the terms of each award. Stock Awards that vest based on the satisfaction of time-based service conditions combined with performance criteria generally vest over a three-year service and performance period, based on performance criteria established at the time of the grant of the award. The portion of the Stock Award that is earned may exceed, be equal to or be less than the targeted number of shares subject to the Stock Award depending on whether the performance criteria are met. Stock Awards activity for the three months ended March 31, 2018, is summarized below: Weighted- average grant Performance date fair and value Time-based time-based Total per share Unvested restricted stock units outstanding as of December 31, 2017 42,028 13,109 55,137 $ 90.05 Granted 20,049 — 20,049 122.00 Vested (1,836 ) (4,370 ) (6,206 ) 87.38 Forfeited/canceled (546 ) — (546 ) 91.52 Unvested restricted stock units outstanding as of March 31, 2018 (1) 59,695 8,739 68,434 $ 99.64 Unvested and expected to vest restricted stock units outstanding as of March 31, 2018 63,143 $ 99.79 Unvested restricted stock awards outstanding as of December 31, 2017 20,789 20,785 41,574 $ 91.52 Granted 21,222 31,830 53,052 122.00 Vested — (6,928 ) (6,928 ) 91.52 Forfeited/canceled — — — — Unvested restricted stock awards outstanding as of March 31, 2018 (1) 42,011 45,687 87,698 $ 108.30 Unvested and expected to vest restricted stock awards outstanding as of March 31, 2018 67,432 $ 108.07 (1) Outstanding restricted stock units and restricted stock awards are based on the maximum payout of the targeted number of shares. As of March 31, 2018, the unrecognized compensation cost related to unvested employee restricted stock units and restricted stock awards was $14,765, excluding estimated forfeitures. This amount is expected to be recognized over a weighted-average period of 3.1 years. Employee stock purchase plan The Company’s 2014 Employee Stock Purchase Plan (ESPP) provides for the grant to all eligible employees an option to purchase stock under the ESPP, within the meaning Section 423 of the Internal Revenue Code. The ESPP permits participants to purchase common stock through payroll deductions of up to 15% of their eligible compensation, which includes a participant’s base straight time gross earnings, incentive compensation, bonuses, overtime and shift premium, but exclusive of payments for equity compensation and other similar compensation. A participant may purchase a maximum of 1,500 shares during a purchase period. Amounts deducted and accumulated by the participant are used to purchase shares of the Company’s common stock at the end of each six-month period. The purchase price of the shares will be 85% of the lower of the fair market value of the Company’s common stock on the first trading day of each offering period or on the exercise date. The offering periods are currently approximately six months in length beginning on the first business day on or after March 1 and September 1 of each year and ending on the first business day on or after September 1 and March 1 approximately six months later. As of March 31, 2018, a total of 759,967 shares of common stock were available for sale pursuant to the ESPP. The number of shares available for sale under the ESPP is increased annually on the first day of each fiscal year by an amount equal to the least of: • 179,069 shares; • 1.5% of the outstanding shares of the Company’s common stock on the last day of the Company’s immediately preceding fiscal year; or • such other amount as may be determined by the administrator. For 2018, an additional 179,069 shares were added to the ESPP share reserve pursuant to the provision described above. Stock-based compensation Stock-based compensation expense recognized for the three months ended March 31, 2018 and March 31, 2017 was as follows: Three months ended March 31, 2018 2017 Stock-based compensation expense by type of award: Stock option plan awards $ 1,951 $ 1,744 Restricted stock units and restricted stock awards 1,239 24 Employee stock purchase plan 191 123 Total stock-based compensation expense $ 3,381 $ 1,891 Employee stock-based compensation expense was calculated based on awards of stock options, restricted stock units and restricted stock awards ultimately expected to vest based on the Company’s historical award cancellations. The employee stock-based compensation expense recognized for the three months ended March 31, 2018 and March 31, 2017 has been reduced for estimated forfeitures of stock option plan awards at a rate of 7.3% and 6.9%, respectively. The employee stock-based compensation expense recognized for the three months ended March 31, 2018 has been reduced for estimated forfeitures of restricted stock at a rate of 4.8%. ASC 718 – Compensation-Stock Compensation For the three months ended March 31, 2018 and March 31, 2017, stock-based compensation expense recognized under ASC 718, included in cost of revenue, research and development expense, sales and marketing expense, and general and administrative expense, was as follows: Three months ended March 31, 2018 2017 Cost of revenue $ 273 $ 191 Research and development 331 223 Sales and marketing 548 315 General and administrative 2,229 1,162 Total stock-based compensation expense $ 3,381 $ 1,891 401(k) retirement savings plan The Company maintains a 401(k) retirement savings plan for the benefit of eligible employees. Under the terms of this plan, eligible employees are able to make contributions to the plan on a tax-deferred basis. The Company began matching employees’ contributions, effective January 1, 2017. The Company contributed $230, net of forfeitures, to the 401(k) plan for the three months ended March 31, 2018 and $174, net of forfeitures, for the three months ended March 31, 2017.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	8. Commitments and contingencies Leases and non-cancelable contractual obligations The Company leases its facilities and certain equipment under operating leases that expire through September 2024. As of March 31, 2018, the minimum aggregate payments due under operating leases and specified non-cancelable contractual obligations, which consist of software license and maintenance agreements, are summarized as follows: Operating leases Related party leases Non-cancelable contractual obligations Total Remaining 9 months of 2018 $ 1,334 $ 24 $ 433 $ 1,791 2019 1,923 32 578 2,533 2020 1,520 11 578 2,109 2021 898 — 456 1,354 2022 568 — — 568 Thereafter 874 — — 874 $ 7,117 $ 67 $ 2,045 $ 9,229 As a result of the MedSupport acquisition, the Company leases a property owned by a related party. Rent expense for the property was $8 for the three months ended March 31, 2018. Rent expense of $321 and $262 for the three months ended March 31, 2018 and March 31, 2017, respectively, was included in the accompanying consolidated statements of comprehensive income. Purchase obligations The Company had approximately $48,900 of outstanding purchase orders with its outside vendors and suppliers as of March 31, 2018. Warranty obligations Accruals for estimated standard warranty expenses are made at the time that the associated revenue is recognized. The provisions for estimated warranty obligations are made based on known claims and estimates of additional returns and warranty obligations based on historical data and future expectations. The following table identifies the changes in the Company’s aggregate product warranty liabilities for the three and twelve-month periods ended March 31, 2018 and December 31, 2017, respectively: March 31, December 31, 2018 2017 Product warranty liability at beginning of period $ 6,171 $ 3,480 Accruals for warranties issued 1,841 5,275 Adjustments related to preexisting warranties (including changes in estimates) 200 200 Settlements made (in cash or in kind) (967 ) (2,784 ) Product warranty liability at end of period $ 7,245 $ 6,171 Legislation and HIPAA The healthcare industry is subject to numerous laws and regulations of federal, state and local governments. These laws and regulations include, but are not necessarily limited to, matters such as licensure, accreditation, government healthcare program participation requirements, reimbursement for patient services, and Medicare and Medicaid fraud and abuse. Government activity has continued with respect to investigations and allegations concerning possible violations of fraud and abuse statutes and regulations by healthcare providers. Violations of these laws and regulations could result in exclusion from government healthcare programs together with the imposition of significant fines and penalties, as well as significant repayments for patient services previously billed. The Company believes that it is in compliance in all material respects with applicable fraud and abuse regulations and other applicable government laws and regulations. Compliance with such laws and regulations can be subject to future government review and interpretation as well as regulatory actions unknown or unasserted at this time. The Health Insurance Portability and Accountability Act of 1996 (HIPAA) ensures health insurance portability, reduces healthcare fraud and abuse, guarantees security and privacy of health information, and enforces standards for health information. The Health Information Technology for Economic and Clinical Health Act (HITECH Act) imposes notification requirements of certain security breaches relating to protected health information. The Company believes that it complies in all material respects with the provisions of those regulations that are applicable to the Company’s business. Legal proceedings The Company is party to various legal proceedings arising in the normal course of business. The Company carries insurance, subject to specified deductibles under the policies, to protect against losses from certain liabilities and costs. At this time, the Company does not anticipate that any of these other proceedings will have a material adverse effect on the Company’s business. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors.

Foreign Currency Exchange Contr

Foreign Currency Exchange Contracts and Hedging	3 Months Ended
	Mar. 31, 2018
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Foreign currency exchange contracts and hedging	9. Foreign currency exchange contracts and hedging As of March 31, 2018 and March 31, 2017, the Company’s total non-designated and designated derivative contracts had notional amounts totaling approximately $2,397 and $17,885, respectively, and $1,620 and $7,378, respectively. These contracts were comprised of offsetting contracts with the same counterparty, each expires within one to nine months, and had an unrealized loss of approximately $77, net of tax, and $3, net of tax, during the three months ended March 31, 2018 and March 31, 2017, respectively. The nonperformance risk of the Company and the counterparty did not have a material impact on the fair value of the derivatives. During the three months ended March 31, 2018 and March 31, 2017, the ineffective portion relating to these hedges was immaterial and the hedges remained effective through their respective settlement dates. As of March 31, 2018, the Company had twenty-six designated hedges and three non-designated hedges. As of March 31, 2017, the Company had twelve designated hedges and three non-designated hedges.

Basis of Presentation and Sum17

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Consolidation	Basis of consolidation The consolidated financial statements include the accounts of Inogen, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated.
Use of Estimates	Use of estimates The preparation of consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Management bases these estimates and assumptions upon historical experience, existing and known circumstances, authoritative accounting pronouncements and other factors that management believes to be reasonable. Significant areas requiring the use of management estimates relate to revenue recognition and determining the stand-alone selling price (SSP) of performance obligations, inventory and rental asset valuations and write-downs, accounts receivable allowances for bad debts, returns and adjustments, warranty expense, stock compensation expense, depreciation and amortization, income tax provision and uncertain tax positions, fair value of financial instruments, and fair value of acquired intangible assets and goodwill. Actual results could differ from these estimates.
Revenue	Revenue The Company generates revenue primarily from sales and rentals of its products. The Company’s products consist of its proprietary line of oxygen concentrators and related accessories. Other revenue, which is included in sales revenue on the Consolidated Statements of Comprehensive Income, consists of repair services and freight revenue for product shipments. Sales revenue Revenue is recognized upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services. Revenue from product sales is generally recognized upon shipment of the product but is deferred for certain transactions when control has not yet transferred to the customer. The Company’s product is generally sold with a right of return and the Company may provide other incentives, which are accounted for as variable consideration when estimating the amount of revenue to recognize. Returns and incentives are estimated at the time sales revenue is recognized. The provisions for estimated returns are made based on known claims and estimates of additional returns based on historical data and future expectations. Sales revenue incentives within the Company’s contracts are estimated based on the most likely amounts expected on the related sales transaction and recorded as a reduction to revenue at the time of sale in accordance with the terms of the contract. The Company also offers a lifetime warranty for direct-to-consumer sales of its portable concentrators. For a fixed price, the Company agrees to provide a fully functional portable oxygen concentrator for the remaining life of the patient. Lifetime warranties are only offered to patients upon the initial sale of portable oxygen concentrators by the Company and are non-transferable. Lifetime warranties are considered to be a distinct performance obligation that are accounted for separately from its sale of portable oxygen concentrators with a standard warranty of three years . The revenue is allocated to the distinct lifetime warranty performance obligation based on a relative SSP method. The Company has vendor-specific objective evidence of the selling price for its equipment. To determine the selling price of the lifetime warranty, the Company uses its best estimate of the SSP for the distinct performance obligation as the lifetime warranty is neither separately priced nor is the selling price available through third-party evidence. To calculate the selling price associated with the lifetime warranties, management considered the profit margins of the overall business, the average estimated cost of lifetime warranties and the price of extended warranties. Revenue from the distinct lifetime warranty is deferred after the delivery of the equipment for three years and recognized on a straight-line basis during the fourth and fifth year, which is the estimated usage period of the contract based on the average patient life expectancy. Revenue from the sale of the Company’s repair services is recognized when the performance obligations are satisfied and collection of the receivables is probable. Other revenue from sale of replacement parts and non-warranty repair services is generally recognized when product is shipped to customers. Freight revenue consists of fees associated with the deployment of products internationally and domestically when expedited freight options are requested or when minimum order quantities are not met. Freight revenue is generally recognized upon shipment of the product but is deferred if control has not yet transferred to the customer. Shipping and handling costs for sold products and rental assets shipped to the Company’s customers are included on the Consolidated Statements of Comprehensive Income as part of cost of sales revenue and cost of rental revenue, respectively. The payment terms and conditions of customer contracts vary by customer type and the products and services offered. For certain products or services and customer types, the Company requires payment before the products or services are delivered to the customer. The timing of sales revenue recognition, billing and cash collection results in billed accounts receivable and deferred revenue in the consolidated balance sheet. Contract liabilities primarily consist of deferred revenue related to lifetime warranties on direct-to-consumer sales revenue when cash payments are received in advance of services performed under the contract. The contract with the customer states the final terms of the sale, including the description, quantity, and price of each product or service purchase. The increase in deferred revenue related to lifetime warranties for the three months ended March 31, 2018 is primarily driven by $1,459 of cash payments received in advance of satisfying the . The Company elected to apply the practical expedient in accordance with ASC 606 and did not evaluate contracts of one year or less for the existence of a significant financing component The Company’s sales revenue is primarily derived from the sale of its Inogen One systems, Inogen At Home systems, and related accessories to individual consumers, HME providers, distributors, the Company’s private label partner and resellers worldwide. Sales revenue is classified into two areas: business-to-business sales and direct-to-consumer sales. The following table sets forth the Company’s sales revenue disaggregated by sales channel and geographic region: Three months ended March 31, Revenue by region and category 2018 2017 Business-to-business domestic sales $ 28,016 $ 17,461 Business-to-business international sales 16,906 11,423 Direct-to-consumer domestic sales 28,662 17,082 Total sales revenue $ 73,584 $ 45,966 Rental revenue The Company recognizes equipment rental revenue over the non-cancelable lease term, which is one month, less estimated adjustments, in accordance with Accounting Standards Codification (ASC) — Leases The lease term begins on the date products are shipped to patients and are recorded at amounts estimated to be received under reimbursement arrangements with third-party payors, including Medicare, private payors, and Medicaid. Due to the nature of the industry and the reimbursement environment in which the Company operates, certain estimates are required to record net revenue and accounts receivable at their net realizable values. Inherent in these estimates is the risk that they will have to be revised or updated as additional information becomes available. Specifically, the complexity of many third-party billing arrangements and the uncertainty of reimbursement amounts for certain services from certain payors may result in adjustments to amounts originally recorded. Such adjustments are typically identified and recorded at the point of cash application, claim denial or account review. The Company adjusts revenue for historical trends on revenue adjustments due to timely filings, deaths, hospice, and other types of analyzable adjustments on a monthly basis. Accounts receivable are reduced by an allowance for doubtful accounts which provides for those accounts from which payment is not expected to be received although product was delivered, and revenue was earned. The determination that an account is uncollectible, and the ultimate write-off of that account occurs once collection is considered to be not probable, and it is written-off and charged to the allowance at that time. Amounts billed but not earned due to the timing of the billing cycle are deferred and recognized in rental revenue on a straight-line basis over the monthly billing period. For example, if the first day of the billing period does not fall on the first of the month, then a portion of the monthly billing period will fall in the subsequent month and the related revenue and cost would be deferred based on the service days in the following month. Rental revenue is recognized as upon transfer of control of promised products or services to customers in an amount that reflects the consideration the Company expects to receive in exchange for those products or services, less estimated adjustments. Revenue not billed at the end of the period is reviewed for the probability of collection and accrued if collection is probable. Rental revenue is not guaranteed, and payment will cease if the patient no longer needs oxygen or returns the equipment. Rental revenue is recognized at estimated allowable amounts that reflect the full consideration the Company expects to receive in exchange for the equipment; transfers to secondary insurances or patient responsibility have no net effect on revenue. Rental revenue is earned for that entire month if the patient is on service on the first day of the 30-day period commencing on the recurring date of service for a particular claim, regardless if there is a change in condition or death after that date. Included in rental revenue are unbilled amounts for which the revenue recognition criteria had been met as of period-end but were not yet billed to the payor. The estimate of net unbilled rental revenue recognized is based on historical trends and estimates of future collectability. In addition, the Company estimates potential future adjustments and write-offs of these unbilled amounts and includes these estimates in the allowance for adjustments and write-offs of rental revenue which is netted against gross receivables.
Recently Issued Accounting Pronouncements Not Yet Adopted	Recently issued accounting pronouncements not yet adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) Land Easement Practice Expedient for Transition to Topic 842 In June 2016, the FASB issued ASU No. 2016-13, Accounting for Credit Losses (Topic 326) In January 2017, the FASB issued ASU No. 2017-04, Simplifying the Test for Goodwill Impairment In August 2017, the FASB issued ASU No. 2017-12, Derivatives and Hedging In January 2018, the FASB issued ASU No. 2018-02, Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income
Recently Adopted Accounting Pronouncements	Recently adopted accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers Revenue with Contracts with Customers: Principal versus Agent Considerations (Reporting Revenue Gross versus Net) In January 2017, the FASB issued ASU No. 2017-01, Clarifying the Definition of a Business
Business Segments	Business segments The Company operates and reports in only one operating and reportable segment – development, manufacturing, marketing, sales, and rental of respiratory products. Management reports financial information on a consolidated basis to the Company’s chief operating decision maker.

Basis of Presentation and Sum18

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Sales Revenue Disaggregated by Sales Channel and Geographic Region	The following table sets forth the Company’s sales revenue disaggregated by sales channel and geographic region: Three months ended March 31, Revenue by region and category 2018 2017 Business-to-business domestic sales $ 28,016 $ 17,461 Business-to-business international sales 16,906 11,423 Direct-to-consumer domestic sales 28,662 17,082 Total sales revenue $ 73,584 $ 45,966

Fair Value of Financial Instr19

Fair Value of Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Summary of Fair Value Assets Measured on Recurring Basis for Cash, Cash Equivalents and Marketable Securities	The following table summarizes fair value measurements by level for the assets measured at fair value on a recurring basis for cash, cash equivalents and marketable securities: As of March 31, 2018 Gross Cash Adjusted unrealized and cash Marketable cost losses Fair value equivalents securities Cash $ 43,188 $ — $ 43,188 $ 43,188 $ — Level 1: Money market accounts 107,906 — 107,906 107,906 — Level 2: Certificates of deposit 11,652 (1 ) 11,651 3,190 8,461 Corporate bonds 22,086 (43 ) 22,043 — 22,043 Agency mortgage-backed securities 1,005 — 1,005 — 1,005 U.S. Treasury securities 2,503 — 2,503 — 2,503 Total $ 188,340 $ (44 ) $ 188,296 $ 154,284 $ 34,012 As of December 31, 2017 Gross Cash Adjusted unrealized and cash Marketable cost losses Fair value equivalents securities Cash $ 46,237 $ — $ 46,237 $ 46,237 $ — Level 1: Money market accounts 93,430 — 93,430 93,430 — Level 2: Certificates of deposit 11,010 (4 ) 11,006 490 10,516 Corporate bonds 20,789 (21 ) 20,768 2,796 17,972 Agency mortgage-backed securities 2,005 (1 ) 2,004 — 2,004 U.S. Treasury securities 499 — 499 — 499 Total $ 173,970 $ (26 ) $ 173,944 $ 142,953 $ 30,991
Summary of Estimated Fair Value of Company's Investments in Marketable Debt Securities, Accounted for as Available-for-Sale Securities	The following table summarizes the estimated fair value of the Company’s investments in marketable securities, accounted for as available-for-sale securities and classified by the contractual maturity date of the securities: March 31, 2018 Due within one year $ 34,012
Summary of Components of Accumulated Other Comprehensive Income (Loss)	The components of accumulated other comprehensive income (loss) were as follows: Foreign Unrealized Unrealized Accumulated currency losses on losses other translation available-for- on cash comprehensive adjustments sale investments flow hedges income Balance as of December 31, 2017 $ 363 $ (17 ) $ (74 ) $ 272 Other comprehensive gain (loss) 108 (19 ) (77 ) 12 Balance as of March 31, 2018 $ 471 $ (36 ) $ (151 ) $ 284

Balance Sheet Components (Table

Balance Sheet Components (Tables)	3 Months Ended
	Mar. 31, 2018
Balance Sheet Related Disclosures [Abstract]
Summary of Cash, Cash Equivalents and Short-term Investments	Cash, cash equivalents and marketable securities consist of the following: March 31, December 31, Cash and cash equivalents 2018 2017 Cash $ 43,188 $ 46,237 Money market accounts 107,906 93,430 Certificates of deposit 3,190 490 Corporate bonds — 2,796 Total cash and cash equivalents $ 154,284 $ 142,953 Marketable securities Certificates of deposit $ 8,461 $ 10,516 Corporate bonds 22,043 17,972 Agency mortgage-backed securities 1,005 2,004 U.S. Treasury securities 2,503 499 Total marketable securities $ 34,012 $ 30,991
Schedule of Gross Accounts Receivable Balance Concentrations by Major Category	Gross accounts receivable balance concentrations by major category as of March 31, 2018 and December 31, 2017 were as follows: March 31, December 31, Gross accounts receivable 2018 2017 Rental (1) $ 6,143 $ 6,236 Business-to-business & other receivables (2) 32,945 28,474 Total gross accounts receivable $ 39,088 $ 34,710 (1) Rental includes Medicare, Medicaid/other government, private insurance and patient pay. (2) Business-to-business receivables included one customer with a gross accounts receivable balance of $9,461 and $10,394 as of March 31, 2018 and December 31, 2017, respectively. This customer received extended payment terms through a direct financing plan offered. The Company also has a credit insurance policy in place, which allocated up to $18,000 in coverage as of March 31, 2018 and allocated up to $12,000 in coverage as of December 31, 2017 for this customer with a $1,000 deductible and 10% retention.
Schedule of Net Accounts Receivable Balance Concentrations by Major Category	Net accounts receivable (gross accounts receivable, net of allowances) balance concentrations by major category as of March 31, 2018 and December 31, 2017 were as follows: March 31, December 31, Net accounts receivable 2018 2017 Rental (1) $ 3,695 $ 4,212 Business-to-business & other receivables (2) 31,394 27,232 Total net accounts receivable $ 35,089 $ 31,444 (1) Rental includes Medicare, Medicaid/other government, private insurance and patient pay. (2) Business-to-business receivables included one customer with a gross accounts receivable balance of $9,461 and $10,394 as of March 31, 2018 and December 31, 2017, respectively. This customer received extended payment terms through a direct financing plan offered. The Company also has a credit insurance policy in place, which allocated up to $18,000 in coverage as of March 31, 2018 and allocated up to $12,000 in coverage as of December 31, 2017 for this customer with a $1,000 deductible and 10% retention.
Schedule of Allowances for Accounts Receivable	The following tables set forth the accounts receivable allowances as of March 31, 2018 and December 31, 2017: March 31, December 31, Allowances - accounts receivable 2018 2017 Doubtful accounts $ 1,589 $ 1,415 Rental revenue adjustments 1,013 947 Sales returns 1,397 904 Total allowances - accounts receivable $ 3,999 $ 3,266
Breakdown of Company's Revenue from U.S. and Non-U.S. Sources	A portion of revenue is earned from sales outside the United States. Approximately 76.9% and 72.2% of the non-U.S. revenue for the three months ended March 31, 2018 and March 31, 2017, respectively, were invoiced in Euros. A breakdown of the Company’s revenue from U.S. and non-U.S. sources for the three months ended March 31, 2018 and March 31, 2017 is as follows: Three months ended March 31, 2018 2017 U.S. revenue $ 62,145 $ 41,077 Non-U.S. revenue 16,906 11,423 Total revenue $ 79,051 $ 52,500
Schedule of Inventories	Inventories that are considered current consist of the following: March 31, December 31, 2018 2017 Raw materials and work-in-progress $ 18,814 $ 16,324 Finished goods 4,640 2,917 Less: reserves (489 ) (399 ) Inventories $ 22,965 $ 18,842
Computation of Depreciation and Amortization using Straight Line Method Over Estimated Useful Lives of Assets	Property and equipment are stated at cost. Depreciation and amortization are calculated using the straight-line method over the assets’ estimated useful lives as follows: Rental equipment 1.5-5 years Manufacturing equipment and tooling 2-5 years Computer equipment and software 2-3 years Furniture and equipment 3-5 years Leasehold improvements Lesser of estimated useful life or remaining lease term
Summary of Depreciation and Amortization Expense of Rental Equipment and Other Property and Equipment	Depreciation and amortization expense related to rental equipment and other property and equipment are summarized below for the three months ended March 31, 2018 and March 31, 2017, respectively. Three months ended March 31, 2018 2017 Rental equipment $ 2,165 $ 2,689 Other property and equipment 530 488 Total depreciation and amortization $ 2,695 $ 3,177
Summary of Property Plant and Equipment and Rental Equipment with Associated Accumulated Depreciation	Property and equipment and rental equipment with associated accumulated depreciation are summarized below for March 31, 2018 and December 31, 2017, respectively. March 31, December 31, Property and equipment 2018 2017 Rental equipment, net of allowances of $754 and $754, respectively $ 47,420 $ 49,349 Other property and equipment 17,387 15,219 Property and equipment 64,807 64,568 Accumulated depreciation Rental equipment 33,671 34,754 Other property and equipment 10,238 9,711 Accumulated depreciation 43,909 44,465 Property and equipment, net Rental equipment, net of allowances of $754 and $754, respectively 13,749 14,595 Other property and equipment 7,149 5,508 Property and equipment, net $ 20,898 $ 20,103
Schedule of Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the three months ended March 31, 2018 were as follows: Balance as of December 31, 2017 $ 2,363 Translation adjustment 67 Balance as of March 31, 2018 $ 2,430
Summary of Intangible Assets	The following tables represent the net carrying values of intangible assets as of the respective dates: Average estimated Gross useful lives carrying Accumulated March 31, 2018 (in years) amount amortization Net amount Licenses 10 $ 185 $ 142 $ 43 Patents and websites 5 4,173 1,131 3,042 Customer relationships 4 1,479 339 1,140 Non-compete agreement 3 246 75 171 Commercials 2-3 303 243 60 Total $ 6,386 $ 1,930 $ 4,456 Average estimated Gross useful lives carrying Accumulated December 31, 2017 (in years) amount amortization Net amount Licenses 10 $ 185 $ 137 $ 48 Patents and websites 5 4,173 959 3,214 Customer relationships 4 1,437 240 1,197 Non-compete agreement 3 240 52 188 Commercials 2-3 303 233 70 Total $ 6,338 $ 1,621 $ 4,717
Schedule of Annual Estimated Amortization Expense for Intangibles	Annual estimated amortization expense for intangibles for each of the succeeding fiscal years is summarized as follows: March 31, 2018 Remaining 9 months of 2018 $ 906 2019 1,147 2020 1,069 2021 790 2022 544 Thereafter — $ 4,456
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses as of March 31, 2018 and December 31, 2017 consisted of the following: March 31, December 31, 2018 2017 Accounts payable $ 13,589 $ 9,541 Accrued inventory (in-transit and unvouchered receipts) and trade payables 7,644 7,252 Accrued purchasing card liability 2,089 2,381 Accrued franchise, sales and use taxes 498 479 Other accrued expenses 940 973 Accounts payable and accrued expenses $ 24,760 $ 20,626
Schedule of Accrued Payroll	Accrued payroll as of March 31, 2018 and December 31, 2017 consisted of the following: March 31, December 31, 2018 2017 Accrued bonuses $ 1,306 $ 3,086 Accrued wages and other payroll related items 3,803 2,453 Accrued vacation 1,498 1,338 Accrued payroll $ 6,607 $ 6,877

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Computation of Earnings Per Share	The computation of EPS is as follows: Three months ended March 31, 2018 2017 Numerator—basic and diluted: Net income $ 10,758 $ 5,932 Denominator: Weighted-average common shares - basic common stock (1) 21,026,154 20,489,532 Weighted-average common shares - diluted common stock 22,295,213 21,579,721 Net income per share - basic common stock $ 0.51 $ 0.29 Net income per share - diluted common stock $ 0.48 $ 0.27 Denominator calculation from basic to diluted: Weighted-average common shares - basic common stock (1) 21,026,154 20,489,532 Stock options and other dilutive awards 1,269,059 1,090,189 Weighted-average common shares - diluted common stock 22,295,213 21,579,721 Shares excluded from diluted weighted-average shares: Stock options — 25,700 Restricted stock units and restricted stock awards 75,926 — Shares excluded from diluted weighted-average shares 75,926 25,700 (1) Unvested restricted stock units and restricted stock awards are not included as shares outstanding in the calculation of basic earnings per share. Vested restricted stock units and restricted stock awards are included in basic earnings per share if all vesting and performance criteria have been met. Performance-based restricted stock units and restricted stock awards are included in the number of shares used to calculate diluted earnings per share as long as all applicable performance criteria are met, and their effect is dilutive. Restricted stock awards are eligible to receive all dividends declared on the Company’s common shares during the vesting period; however, such dividends are not paid until the restrictions lapse.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Summary of Stock Options Activity	The activity for stock options under the Company’s stock plans is as follows: Remaining weighted- Weighted- average Per share average contractual average Price per exercise terms intrinsic Options share price (in years) value Outstanding as of December 31, 2017 1,836,426 $0.60-$83.30 $ 30.77 4.58 $ 88.31 Granted — — — Exercised (169,594 ) 0.60-58.95 26.29 Forfeited — — — Expired — — — Outstanding as of March 31, 2018 1,666,832 $0.60-$83.30 $ 31.23 4.45 $ 91.61 Vested and exercisable as of March 31, 2018 1,134,940 $0.60-$83.30 $ 25.82 4.31 $ 97.02 Vested and expected to vest as of March 31, 2018 1,631,773 $0.60-$83.30 $ 30.98 4.44 $ 91.86
Summary of Restricted Stock Activity	Stock Awards activity for the three months ended March 31, 2018, is summarized below: Weighted- average grant Performance date fair and value Time-based time-based Total per share Unvested restricted stock units outstanding as of December 31, 2017 42,028 13,109 55,137 $ 90.05 Granted 20,049 — 20,049 122.00 Vested (1,836 ) (4,370 ) (6,206 ) 87.38 Forfeited/canceled (546 ) — (546 ) 91.52 Unvested restricted stock units outstanding as of March 31, 2018 (1) 59,695 8,739 68,434 $ 99.64 Unvested and expected to vest restricted stock units outstanding as of March 31, 2018 63,143 $ 99.79 Unvested restricted stock awards outstanding as of December 31, 2017 20,789 20,785 41,574 $ 91.52 Granted 21,222 31,830 53,052 122.00 Vested — (6,928 ) (6,928 ) 91.52 Forfeited/canceled — — — — Unvested restricted stock awards outstanding as of March 31, 2018 (1) 42,011 45,687 87,698 $ 108.30 Unvested and expected to vest restricted stock awards outstanding as of March 31, 2018 67,432 $ 108.07 (1) Outstanding restricted stock units and restricted stock awards are based on the maximum payout of the targeted number of shares.
Summary of Stock-based Compensation Expense	Stock-based compensation Stock-based compensation expense recognized for the three months ended March 31, 2018 and March 31, 2017 was as follows: Three months ended March 31, 2018 2017 Stock-based compensation expense by type of award: Stock option plan awards $ 1,951 $ 1,744 Restricted stock units and restricted stock awards 1,239 24 Employee stock purchase plan 191 123 Total stock-based compensation expense $ 3,381 $ 1,891 For the three months ended March 31, 2018 and March 31, 2017, stock-based compensation expense recognized under ASC 718, included in cost of revenue, research and development expense, sales and marketing expense, and general and administrative expense, was as follows: Three months ended March 31, 2018 2017 Cost of revenue $ 273 $ 191 Research and development 331 223 Sales and marketing 548 315 General and administrative 2,229 1,162 Total stock-based compensation expense $ 3,381 $ 1,891

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments And Contingencies Disclosure [Abstract]
Minimum Aggregate Payments Due under Operating Leases and Specified Non-Cancelable Contractual Obligations Consist of Software License and Maintenance Agreements	The Company leases its facilities and certain equipment under operating leases that expire through September 2024. As of March 31, 2018, the minimum aggregate payments due under operating leases and specified non-cancelable contractual obligations, which consist of software license and maintenance agreements, are summarized as follows: Operating leases Related party leases Non-cancelable contractual obligations Total Remaining 9 months of 2018 $ 1,334 $ 24 $ 433 $ 1,791 2019 1,923 32 578 2,533 2020 1,520 11 578 2,109 2021 898 — 456 1,354 2022 568 — — 568 Thereafter 874 — — 874 $ 7,117 $ 67 $ 2,045 $ 9,229
Schedule of Changes in Aggregate Product Warranty Liabilities	Accruals for estimated standard warranty expenses are made at the time that the associated revenue is recognized. The provisions for estimated warranty obligations are made based on known claims and estimates of additional returns and warranty obligations based on historical data and future expectations. The following table identifies the changes in the Company’s aggregate product warranty liabilities for the three and twelve-month periods ended March 31, 2018 and December 31, 2017, respectively: March 31, December 31, 2018 2017 Product warranty liability at beginning of period $ 6,171 $ 3,480 Accruals for warranties issued 1,841 5,275 Adjustments related to preexisting warranties (including changes in estimates) 200 200 Settlements made (in cash or in kind) (967 ) (2,784 ) Product warranty liability at end of period $ 7,245 $ 6,171

Business Overview - Additional

Business Overview - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018Productlb
Business Overview Disclosures [Line Items]
Percentage of patients using portable oxygen concentrators	9.10%
Inogen Europe Holding B.V.
Business Overview Disclosures [Line Items]
Date of incorporation of subsidiary	Apr. 13, 2017
One G4
Business Overview Disclosures [Line Items]
Weight of oxygen portable device	2.8
One G3
Business Overview Disclosures [Line Items]
Weight of oxygen portable device	4.8
One G2
Business Overview Disclosures [Line Items]
Weight of oxygen portable device	7
Maximum | One G4
Business Overview Disclosures [Line Items]
Estimated battery life of portable oxygen concentrator	2 hours 36 minutes
Maximum | One G3
Business Overview Disclosures [Line Items]
Estimated battery life of portable oxygen concentrator	4 hours 42 minutes
Maximum | One G2
Business Overview Disclosures [Line Items]
Estimated battery life of portable oxygen concentrator	5 hours
Minimum | Inogen One
Business Overview Disclosures [Line Items]
Number of portable oxygen concentrators | Product	409,000

Basis of Presentation and Sum25

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)Segment	Dec. 31, 2017USD ($)
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Standard warranty period offered	3 years
Cash payments received in advance of satisfying distinct performance obligation	$ 1,459
Performance obligation offset of revenue recognized	$ 286
Rental revenue earned	30-day period
Number of operating segments | Segment	1
Number of reportable segments | Segment	1
Lifetime Warranties | Direct-to-Consumer
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Sales revenue	$ 11,993	$ 10,820

Basis of Presentation and Sum26

Basis of Presentation and Summary of Significant Accounting Policies - Sales Revenue Disaggregated by Sales Channel and Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation Of Revenue [Line Items]
Sales revenue	$ 73,584	$ 45,966
Business to Business | Domestic
Disaggregation Of Revenue [Line Items]
Sales revenue	28,016	17,461
Business to Business | International
Disaggregation Of Revenue [Line Items]
Sales revenue	16,906	11,423
Direct-to-Consumer | Domestic
Disaggregation Of Revenue [Line Items]
Sales revenue	$ 28,662	$ 17,082

Fair Value of Financial Instr27

Fair Value of Financial Instruments - Summary of Fair Value Assets Measured on Recurring Basis for Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 34,012	$ 30,991
Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	188,340	173,970
Gross unrealized losses	(44)	(26)
Fair value	188,296	173,944
Cash and cash equivalents	154,284	142,953
Marketable securities	34,012	30,991
Fair Value Measurements Recurring | Cash
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	43,188	46,237
Fair value	43,188	46,237
Cash and cash equivalents	43,188	46,237
Fair Value Measurements Recurring | Level 1 | Money Market Accounts
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	107,906	93,430
Fair value	107,906	93,430
Cash and cash equivalents	107,906	93,430
Fair Value Measurements Recurring | Level 2 | Certificates Of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	11,652	11,010
Gross unrealized losses	(1)	(4)
Fair value	11,651	11,006
Cash and cash equivalents	3,190	490
Marketable securities	8,461	10,516
Fair Value Measurements Recurring | Level 2 | Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	22,086	20,789
Gross unrealized losses	(43)	(21)
Fair value	22,043	20,768
Cash and cash equivalents		2,796
Marketable securities	22,043	17,972
Fair Value Measurements Recurring | Level 2 | Agency Mortgage-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	1,005	2,005
Gross unrealized losses		(1)
Fair value	1,005	2,004
Marketable securities	1,005	2,004
Fair Value Measurements Recurring | Level 2 | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Adjusted cost	2,503	499
Fair value	2,503	499
Marketable securities	$ 2,503	$ 499

Fair Value of Financial Instr28

Fair Value of Financial Instruments - Summary of Estimated Fair Value of Company's Investments in Marketable Securities, Accounted for as Available-for-Sale Securities (Details) $ in Thousands	Mar. 31, 2018USD ($)
Available For Sale Securities [Abstract]
Due within one year	$ 34,012

Fair Value of Financial Instr29

Fair Value of Financial Instruments - Additional Information (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Forward Contracts
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Related payable	$ 255	$ 66

Fair Value of Financial Instr30

Fair Value of Financial Instruments - Summary of Components of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	$ 227,041	$ 182,088
Other comprehensive gain (loss)	12	61
Ending Balance	246,337	192,775
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	363
Other comprehensive gain (loss)	108
Ending Balance	471
Unrealized Losses on Available-for-sale Investments
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(17)
Other comprehensive gain (loss)	(19)
Ending Balance	(36)
Unrealized Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	(74)
Other comprehensive gain (loss)	(77)
Ending Balance	(151)
Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning Balance	272	(35)
Other comprehensive gain (loss)	12	61
Ending Balance	$ 284	$ 26

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Cash, Cash Equivalents and Short-term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and cash equivalents
Cash	$ 43,188	$ 46,237
Money market accounts	107,906	93,430
Certificates of deposit	3,190	490
Corporate bonds		2,796
Total cash and cash equivalents	154,284	142,953	$ 105,105	$ 92,851
Marketable securities
Marketable securities	34,012	30,991
Certificates Of Deposit
Marketable securities
Marketable securities	8,461	10,516
Corporate Bonds
Marketable securities
Marketable securities	22,043	17,972
Agency Mortgage-backed Securities
Marketable securities
Marketable securities	1,005	2,004
U.S. Treasury Securities
Marketable securities
Marketable securities	$ 2,503	$ 499

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Details)	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)Customer	Mar. 31, 2017USD ($)Customer	Dec. 31, 2017USD ($)Customer
Schedule Of Balance Sheet Components [Line Items]
Unbilled Receivables	$ 1,299,000		$ 1,470,000
Accounts receivable, net	$ 35,089,000		31,444,000
Percentage of Non-US revenue invoiced in Euros	76.90%	72.20%
Noncurrent inventories expected to be realized or consumed	$ 452,000		644,000
Salvage value of expenditures for additions, improvements and replacements	0
Repairs and maintenance expense	560,000	$ 651,000
Depreciation and amortization	2,695,000	3,177,000
Impairments of long-lived assets	0	0
Impairment of finite lived intangible assets	0	0
Amortization of intangible assets	298,000	27,000
Construction in Process and Computer Software or Development Cost
Schedule Of Balance Sheet Components [Line Items]
Depreciation and amortization	0	$ 0
Customer Concentration Risk | Customer One
Schedule Of Balance Sheet Components [Line Items]
Accounts receivable, net	9,461,000		10,394,000
Customer Concentration Risk | Customer Two
Schedule Of Balance Sheet Components [Line Items]
Accounts receivable, net	$ 8,077,000		$ 6,459,000
Sales Revenue, Net | Customer Concentration Risk
Schedule Of Balance Sheet Components [Line Items]
Number of customers | Customer	1	1
Net Accounts Receivable | Customer Concentration Risk
Schedule Of Balance Sheet Components [Line Items]
Number of customers | Customer	2		2
Raw materials | Supplier Concentration Risk | Vendor one
Schedule Of Balance Sheet Components [Line Items]
Concentration risk, percentage	18.50%	18.80%
Raw materials | Supplier Concentration Risk | Vendor two
Schedule Of Balance Sheet Components [Line Items]
Concentration risk, percentage	15.10%	11.60%
Raw materials | Supplier Concentration Risk | Vendor three
Schedule Of Balance Sheet Components [Line Items]
Concentration risk, percentage	12.00%	10.90%

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Gross Accounts Receivable Balance Concentrations by Major Category (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Gross accounts receivable	$ 39,088	$ 34,710
Rental
Accounts Notes And Loans Receivable [Line Items]
Gross accounts receivable	6,143	6,236
Business To Business And Other Receivables
Accounts Notes And Loans Receivable [Line Items]
Gross accounts receivable	$ 32,945	$ 28,474

Balance Sheet Components - Sc34

Balance Sheet Components - Schedule of Net Accounts Receivable Balance Concentrations by Major Category (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Net accounts receivable	$ 35,089	$ 31,444
Rental
Accounts Notes And Loans Receivable [Line Items]
Net accounts receivable	3,695	4,212
Business To Business And Other Receivables
Accounts Notes And Loans Receivable [Line Items]
Net accounts receivable	$ 31,394	$ 27,232

Balance Sheet Components - Sc35

Balance Sheet Components - Schedule of Net Accounts Receivable Balance Concentrations by Major Category (Parenthetical) (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2018USD ($)Customer	Dec. 31, 2017USD ($)Customer
Accounts Notes And Loans Receivable [Line Items]
Accounts receivable, gross	$ 39,088,000	$ 34,710,000
Customer Concentration Risk | Business To Business Receivables
Accounts Notes And Loans Receivable [Line Items]
Number of customers | Customer	1	1
Accounts receivable, gross	$ 9,461,000	$ 10,394,000
Credit insurance policy, deductible amount	$ 1,000,000
Credit insurance policy, retention percentage	10.00%
Customer Concentration Risk | Business To Business Receivables | Maximum
Accounts Notes And Loans Receivable [Line Items]
Credit insurance policy, coverage limit	$ 18,000,000	$ 12,000,000

Balance Sheet Components - Sc36

Balance Sheet Components - Schedule of Allowances for Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Allowances - accounts receivable
Doubtful accounts	$ 1,589	$ 1,415
Rental revenue adjustments	1,013	947
Sales returns	1,397	904
Total allowances - accounts receivable	$ 3,999	$ 3,266

Balance Sheet Components - Brea

Balance Sheet Components - Breakdown of the Company Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Concentration Risk [Line Items]
Revenues	$ 79,051	$ 52,500
U.S. revenue
Concentration Risk [Line Items]
Revenues	62,145	41,077
Non-U.S. revenue
Concentration Risk [Line Items]
Revenues	$ 16,906	$ 11,423

Balance Sheet Components - Sc38

Balance Sheet Components - Schedule of Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials and work-in-progress	$ 18,814	$ 16,324
Finished goods	4,640	2,917
Less: reserves	(489)	(399)
Inventories	$ 22,965	$ 18,842

Balance Sheet Components - Comp

Balance Sheet Components - Computation of Depreciation and Amortization Using Straight Line Method Over Estimated Useful Lives of Assets (Details)	3 Months Ended
	Mar. 31, 2018
Rental equipment | Minimum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	1 year 6 months
Rental equipment | Maximum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	5 years
Manufacturing equipment and tooling | Minimum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	2 years
Manufacturing equipment and tooling | Maximum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	5 years
Computer equipment and software | Minimum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	2 years
Computer equipment and software | Maximum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	3 years
Furniture and equipment | Minimum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	3 years
Furniture and equipment | Maximum
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	5 years
Leasehold improvements
Property Plant And Equipment [Line Items]
Property Plant And Equipment Useful Life	Lesser of estimated useful life or remaining lease term

Balance Sheet Components - Su40

Balance Sheet Components - Summary of Depreciation and Amortization Expense of Rental Equipment and Other Property and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Property Plant And Equipment [Line Items]
Depreciation	$ 2,165	$ 2,689
Depreciation and amortization	2,695	3,177
Equipment
Property Plant And Equipment [Line Items]
Depreciation	2,165	2,689
Other property and equipment
Property Plant And Equipment [Line Items]
Depreciation and amortization	$ 530	$ 488

Balance Sheet Components - Su41

Balance Sheet Components - Summary of Property Plant and Equipment and Rental Equipment with Associated Accumulated Depreciation (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment	$ 64,807	$ 64,568
Accumulated depreciation	43,909	44,465
Property and equipment, net	20,898	20,103
Equipment
Property Plant And Equipment [Line Items]
Property and equipment	47,420	49,349
Accumulated depreciation	33,671	34,754
Property and equipment, net	13,749	14,595
Other property and equipment
Property Plant And Equipment [Line Items]
Property and equipment	17,387	15,219
Accumulated depreciation	10,238	9,711
Property and equipment, net	$ 7,149	$ 5,508

Balance Sheet Components - Su42

Balance Sheet Components - Summary of Property Plant and Equipment and Rental Equipment with Associated Accumulated Depreciation (Parenthetical) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Abstract]
Rental equipment, allowance	$ 754	$ 754

Balance Sheet Components - Sc43

Balance Sheet Components - Schedule of Changes in Carrying Amount of Goodwill (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]
Balance as of December 31, 2017	$ 2,363
Translation adjustment	67
Balance as of March 31, 2018	$ 2,430

Balance Sheet Components - Su44

Balance Sheet Components - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	$ 6,386	$ 6,338
Accumulated amortization	1,930	1,621
Net amount	$ 4,456	$ 4,717
Licenses
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	10 years	10 years
Gross carrying amount	$ 185	$ 185
Accumulated amortization	142	137
Net amount	$ 43	$ 48
Patents And Websites
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	5 years	5 years
Gross carrying amount	$ 4,173	$ 4,173
Accumulated amortization	1,131	959
Net amount	$ 3,042	$ 3,214
Customer Relationships
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	4 years	4 years
Gross carrying amount	$ 1,479	$ 1,437
Accumulated amortization	339	240
Net amount	$ 1,140	$ 1,197
Non-Compete Agreement
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	3 years	3 years
Gross carrying amount	$ 246	$ 240
Accumulated amortization	75	52
Net amount	171	188
Commercials
Finite Lived Intangible Assets [Line Items]
Gross carrying amount	303	303
Accumulated amortization	243	233
Net amount	$ 60	$ 70
Commercials | Minimum
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	2 years	2 years
Commercials | Maximum
Finite Lived Intangible Assets [Line Items]
Average estimated useful lives (in years)	3 years	3 years

Balance Sheet Components - Sc45

Balance Sheet Components - Schedule of Annual Estimated Amortization Expense for Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Remaining 9 months of 2018	$ 906
2,019	1,147
2,020	1,069
2,021	790
2,022	544
Net amount	$ 4,456	$ 4,717

Balance Sheet Components - Sc46

Balance Sheet Components - Schedule of Accounts Payable and Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accounts payable	$ 13,589	$ 9,541
Accrued inventory (in-transit and unvouchered receipts) and trade payables	7,644	7,252
Accrued purchasing card liability	2,089	2,381
Accrued franchise, sales and use taxes	498	479
Other accrued expenses	940	973
Accounts payable and accrued expenses	$ 24,760	$ 20,626

Balance Sheet Components - Sc47

Balance Sheet Components - Schedule of Accrued Payroll (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables And Accruals [Abstract]
Accrued bonuses	$ 1,306	$ 3,086
Accrued wages and other payroll related items	3,803	2,453
Accrued vacation	1,498	1,338
Accrued payroll	$ 6,607	$ 6,877

Earnings per Share - Computatio

Earnings per Share - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Numerator—basic and diluted:
Net income	$ 10,758	$ 5,932
Denominator:
Weighted-average common shares - basic common stock	21,026,154	20,489,532
Weighted-average common shares - diluted common stock	22,295,213	21,579,721
Net income per share - basic common stock	$ 0.51	$ 0.29
Net income per share - diluted common stock	$ 0.48	$ 0.27
Weighted-average number of shares used in calculating net income per share attributable to common stockholders:
Weighted-average common shares - basic common stock	21,026,154	20,489,532
Stock options and other dilutive awards	1,269,059	1,090,189
Weighted-average common shares - diluted common stock	22,295,213	21,579,721
Shares excluded from diluted weighted-average shares:
Shares excluded from diluted weighted-average shares	75,926	25,700
Stock options
Shares excluded from diluted weighted-average shares:
Shares excluded from diluted weighted-average shares		25,700
Restricted stock units and restricted stock awards
Shares excluded from diluted weighted-average shares:
Shares excluded from diluted weighted-average shares	75,926

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, interest or penalties recognized	$ 0		$ 0
Corporate tax rate	21.00%			34.00%
Provisional net charge related to TCJA		$ 7,578,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class Of Stock [Line Items]
Stock-based compensation, unrecognized expense, nonvested granted awards	$ 7,866	$ 13,511
401(k) Retirement Savings Plan
Class Of Stock [Line Items]
Defined benefit plan, contributed by employer net of forfeitures	$ 230	$ 174
Stock options
Class Of Stock [Line Items]
Rate of reduced stock-based compensation expense for estimated forfeiture	7.30%	6.90%
Time based restricted stock units
Class Of Stock [Line Items]
Vesting period	4 years
Time based restricted stock awards
Class Of Stock [Line Items]
Vesting period	4 years
Performance and time based restricted stock awards
Class Of Stock [Line Items]
Vesting period	3 years
Performance and time based restricted stock units
Class Of Stock [Line Items]
Vesting period	3 years
Restricted stock units and restricted stock awards
Class Of Stock [Line Items]
Unrecognized compensation cost related to unvested employee excluding estimated forfeitures	$ 14,765
Amount expected to recognized over weighted-average period	3 years 1 month 6 days
Rate of reduced stock-based compensation expense for estimated forfeiture	4.80%
Maximum | Stock options
Class Of Stock [Line Items]
Stock option period, expiration	10 years
Vesting period	4 years
Minimum | Stock options
Class Of Stock [Line Items]
Stock option period, expiration	7 years
Vesting period	1 year
2002 Plan
Class Of Stock [Line Items]
Stock option shares outstanding	40,508
Number of equity awards available for grant	0
2012 Plan
Class Of Stock [Line Items]
Stock option shares outstanding	306,266
Number of equity awards available for grant	0
2014 Plan
Class Of Stock [Line Items]
Stock option shares outstanding	1,476,190
Number of equity awards available for grant	1,920,713
Terms of shares available for issuance	The number of shares available for issuance under the 2014 Plan also is increased annually on the first day of each fiscal year equal to the least of: 895,346 shares; 4% of the outstanding shares of common stock as of the last day of the Company's immediately preceding fiscal year; or such other amount as the Company's board of directors may determine.
Common stock capital shares reserved for future issuance maximum annual increase	895,346
Percentage on outstanding shares of common stock	4.00%
Number of additional number of shares reserve to provision	839,054
2012 Plan and 2002 Plan | Maximum
Class Of Stock [Line Items]
Stock option shares outstanding	2,328,569
2014 ESPP Plan
Class Of Stock [Line Items]
Number of equity awards available for grant	759,967
Terms of shares available for issuance	The number of shares available for sale under the ESPP is increased annually on the first day of each fiscal year equal to the least of: 179,069 shares; 1.5% of the outstanding shares of the Company’s common stock on the last day of the Company’s immediately preceding fiscal year; or such other amount as may be determined by the administrator.
Percentage on outstanding shares of common stock	1.50%
Number of additional number of shares reserve to provision	179,069
Maximum percentage of common stock eligible to purchase through payroll deductions for participants	15.00%
Maximum number of shares available for participant to purchase during period	1,500
Purchase price as percentage of stock price on offering period	85.00%
Purchase price as percentage of stock price on exercise date	85.00%
Potential increase of shares available for issuance	179,069

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Options Activity (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Stock Options Outstanding, Beginning balance	1,836,426
Stock Options, Exercised	(169,594)
Stock Options Outstanding, Ending balance	1,666,832	1,836,426
Stock Options, Vested and exercisable	1,134,940
Stock Options, Vested and expected to vest	1,631,773
Outstanding, Weighted-average exercise price, Beginning balance	$ 30.77
Weighted-average exercise price, Exercised	26.29
Outstanding, Weighted-average exercise price, Ending balance	31.23	$ 30.77
Weighted-average exercise price, Vested and exercisable	25.82
Weighted-average exercise price, Vested and expected to vest	$ 30.98
Remaining weighted-average contractual term, Outstanding	4 years 5 months 12 days	4 years 6 months 29 days
Remaining weighted-average contractual term, Vested and exercisable	4 years 3 months 21 days
Remaining weighted-average contractual term, Vested and expected to vest	4 years 5 months 8 days
Outstanding, Per share average intrinsic value	$ 91.61	$ 88.31
Per share average intrinsic value, Vested and exercisable	97.02
Per share average intrinsic value, Vested and expected to vest	91.86
Minimum
Class Of Stock [Line Items]
Outstanding, Price per share, Beginning balance	0.60
Price per share, Exercised	0.60
Outstanding, Price per share, Ending balance	0.60	0.60
Price per share, Vested and exercisable	0.60
Price per share, Vested and expected to vest	0.60
Maximum
Class Of Stock [Line Items]
Outstanding, Price per share, Beginning balance	83.30
Price per share, Exercised	58.95
Outstanding, Price per share, Ending balance	83.30	$ 83.30
Price per share, Vested and exercisable	83.30
Price per share, Vested and expected to vest	$ 83.30

Stockholders' Equity - Summar52

Stockholders' Equity - Summary of Restricted Stock Activity (Details)	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Time based restricted stock units
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	42,028
Granted	20,049
Vested	(1,836)
Forfeited/canceled	(546)
Unvested restricted stock units/ awards outstanding, Ending balance	59,695
Performance and time based restricted stock units
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	13,109
Vested	(4,370)
Unvested restricted stock units/ awards outstanding, Ending balance	8,739
Restricted stock units
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	55,137
Granted	20,049
Vested	(6,206)
Forfeited/canceled	(546)
Unvested restricted stock units/ awards outstanding, Ending balance	68,434
Unvested and expected to vest restricted stock units/awards outstanding	63,143
Weighted-average grant date fair value per share, Unvested restricted stock units/ awards outstanding, Beginning balance | $ / shares	$ 90.05
Weighted-average grant date fair value per share, Granted | $ / shares	122
Weighted-average grant date fair value per share, Vested | $ / shares	87.38
Weighted-average grant date fair value per share, Forfeited/canceled | $ / shares	91.52
Weighted-average grant date fair value per share, Unvested restricted stock units/ awards outstanding, Ending balance | $ / shares	99.64
Weighted-average grant date fair value per share, Unvested and expected to vest restricted stock units/awards outstanding | $ / shares	$ 99.79
Time based restricted stock awards
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	20,789
Granted	21,222
Unvested restricted stock units/ awards outstanding, Ending balance	42,011
Performance and time based restricted stock awards
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	20,785
Granted	31,830
Vested	(6,928)
Unvested restricted stock units/ awards outstanding, Ending balance	45,687
Restricted stock awards
Class Of Stock [Line Items]
Unvested restricted stock units/ awards outstanding, Beginning balance	41,574
Granted	53,052
Vested	(6,928)
Unvested restricted stock units/ awards outstanding, Ending balance	87,698
Unvested and expected to vest restricted stock units/awards outstanding	67,432
Weighted-average grant date fair value per share, Unvested restricted stock units/ awards outstanding, Beginning balance | $ / shares	$ 91.52
Weighted-average grant date fair value per share, Granted | $ / shares	122
Weighted-average grant date fair value per share, Vested | $ / shares	91.52
Weighted-average grant date fair value per share, Unvested restricted stock units/ awards outstanding, Ending balance | $ / shares	108.30
Weighted-average grant date fair value per share, Unvested and expected to vest restricted stock units/awards outstanding | $ / shares	$ 108.07

Stockholders' Equity - Summar53

Stockholders' Equity - Summary of Stock-based Compensation Expense Recognized (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation expense by type of award:
Stock-based compensation expense	$ 3,381	$ 1,891
Stock Option Plan Awards
Stock-based compensation expense by type of award:
Stock-based compensation expense	1,951	1,744
Restricted stock units and restricted stock awards
Stock-based compensation expense by type of award:
Stock-based compensation expense	1,239	24
Employee Stock Purchase Plan
Stock-based compensation expense by type of award:
Stock-based compensation expense	$ 191	$ 123

Stockholders' Equity - Summar54

Stockholders' Equity - Summary of Stock-based Compensation Expense Recognized in Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class Of Stock [Line Items]
Stock-based compensation expense	$ 3,381	$ 1,891
Cost of Revenue
Class Of Stock [Line Items]
Stock-based compensation expense	273	191
Research and Development
Class Of Stock [Line Items]
Stock-based compensation expense	331	223
Sales and Marketing
Class Of Stock [Line Items]
Stock-based compensation expense	548	315
General and Administrative
Class Of Stock [Line Items]
Stock-based compensation expense	$ 2,229	$ 1,162

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments And Contingencies [Line Items]
Rent expense	$ 321	$ 262
Outstanding purchase orders with its outside vendors and suppliers	48,900
MedSupport Systems B.V.
Commitments And Contingencies [Line Items]
Rent expense	$ 8
Offices and Certain Equipment
Commitments And Contingencies [Line Items]
Operating leases expiration date	Sep. 30, 2024

Commitments and Contingencies56

Commitments and Contingencies - Minimum Aggregate Payments Due under Operating Leases and Specified Non-Cancelable Contractual Obligations Consist of Software License and Maintenance Agreements (Details) $ in Thousands	Mar. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating leases, Remaining 9 months of 2018	$ 1,334
Operating leases, 2019	1,923
Operating leases, 2020	1,520
Operating leases, 2021	898
Operating leases, 2022	568
Operating leases, Thereafter	874
Operating leases, Total minimum payments	7,117
Related party leases, Remaining 9 months of 2018	24
Related party leases, 2019	32
Related party leases, 2020	11
Related party leases, Total minimum payments	67
Non-cancelable contractual obligations, Remaining 9 months of 2018	433
Non-cancelable contractual obligations, 2019	578
Non-cancelable contractual obligations, 2020	578
Non-cancelable contractual obligations, 2021	456
Non-cancelable contractual obligations, Total minimum payments	2,045
Remaining 9 months of 2018	1,791
2,019	2,533
2,020	2,109
2,021	1,354
2,022	568
Thereafter	874
Total minimum payments	$ 9,229

Commitments and Contingencies57

Commitments and Contingencies - Schedule of Changes in Aggregate Product Warranty Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Product warranty liability at beginning of period	$ 6,171	$ 3,480
Accruals for warranties issued	1,841	5,275
Adjustments related to preexisting warranties (including changes in estimates)	200	200
Settlements made (in cash or in kind)	(967)	(2,784)
Product warranty liability at end of period	$ 7,245	$ 6,171

Foreign Currency Exchange Con58

Foreign Currency Exchange Contracts and Hedging - Additional Information (Details)	3 Months Ended
	Mar. 31, 2018USD ($)Contract	Mar. 31, 2017USD ($)Contract
Derivatives Fair Value [Line Items]
Number of contract designated hedges | Contract	26	12
Number of contract non-designated hedges | Contract	3	3
Non-Designated Derivative Contracts
Derivatives Fair Value [Line Items]
Derivative contracts notional amounts	$ 2,397,000	$ 1,620,000
Designated Derivative Contracts
Derivatives Fair Value [Line Items]
Derivative contracts notional amounts	17,885,000	7,378,000
Unrealized (loss) gain on derivative	$ (77,000)	$ 3,000
Minimum
Derivatives Fair Value [Line Items]
Derivative contracts expiration period	1 month
Maximum
Derivatives Fair Value [Line Items]
Derivative contracts expiration period	9 months