Entellus Medical (ENTL) 10-K 22 Feb 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Feb. 15, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Trading Symbol	ENTL
Entity Registrant Name	ENTELLUS MEDICAL INC
Entity Central Index Key	1,374,128
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		21,877,702
Entity Public Float			$ 137.3

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2016	Dec. 31, 2015
CURRENT ASSETS
Cash and cash equivalents	$ 21,417,000	$ 28,548,000
Short-term investments	10,845,000	38,210,000
Accrued interest income	75,000	247,000
Accounts receivable, net of allowance for doubtful accounts and sales returns of $308 and $386, respectively	13,556,000	10,440,000
Inventories	7,226,000	3,889,000
Prepaid expenses and other current assets	1,787,000	1,691,000
Total current assets	54,906,000	83,025,000
Property and equipment, net	6,487,000	4,126,000
Intangible assets, net	9,840,000
Goodwill	477,000
Other non-current assets	379,000	34,000
Total assets	72,089,000	87,185,000
CURRENT LIABILITIES
Accounts payable	2,796,000	2,208,000
Accrued expenses	13,005,000	6,995,000
Current portion of long-term debt	9,118,000
Total current liabilities	24,919,000	9,203,000
LONG-TERM LIABILITIES
Long-term debt, less current portion, net of debt issuance cost of $116 and $176, respectively	10,766,000	19,824,000
Other non-current liabilities	959,000	562,000
Total liabilities	36,644,000	29,589,000
COMMITMENTS AND CONTINGENCIES (See Note L)
STOCKHOLDERS' EQUITY (See Note H)
Preferred stock, $0.001 par value per share: Authorized shares: 10,000 at December 31, 2016 and December 31, 2015 Issued and outstanding shares: none
Common stock, $0.001 par value per share: Authorized shares: 200,000 at December 31, 2016 and December 31, 2015 Issued and outstanding shares: 18,908 and 18,794 at December 31, 2016 and December 31, 2015, respectively	19,000	19,000
Additional paid-in capital	186,370,000	179,673,000
Accumulated other comprehensive loss	(156,000)	(38,000)
Accumulated deficit	(150,788,000)	(122,058,000)
Total stockholders' equity	35,445,000	57,596,000
Total liabilities and stockholders' equity	$ 72,089,000	$ 87,185,000

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts and sales returns	$ 308	$ 386
Debt issuance cost	$ 116	$ 176
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares Issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	18,908,000	18,794,000
Common stock, shares outstanding	18,908,000	18,794,000

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Revenue	$ 75,184	$ 61,570
Cost of goods sold	18,720	14,058
Gross profit	56,464	47,512
Operating expenses
Selling and marketing	56,827	44,947
Research and development	7,792	5,387
General and administrative	18,560	13,034
Total operating expenses	83,179	63,368
Loss from operations	(26,715)	(15,856)
Other income (expense)
Interest income	278	171
Interest expense	(2,248)	(2,604)
Other non-operating (expense) income	(39)	(11)
Loss before income tax expense	(28,724)	(18,300)
Income tax expense	(6)
Net loss	(28,730)	(18,300)
Other comprehensive loss
Unrealized gain (loss) on short term investments, net of tax	17	(16)
Foreign currency translation loss	(135)	(22)
Comprehensive loss	$ (28,848)	$ (18,338)
Net loss per share, basic and diluted	$ (1.53)	$ (1.06)
Weighted average common shares used to compute net loss per share, basic and diluted	18,839	17,217

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Other Comprehensive Loss [Member]
Balance at Dec. 31, 2013	$ (94,228)	$ 91,554	$ 2	$ 2,599	$ (96,829)
Balance, shares at Dec. 31, 2013		44,317	1,449
Stock options exercised	$ 576			576
Stock options exercised, shares	466		466
Repurchase of common stock	$ (21)			(21)
Repurchase of common stock, shares			(28)
Stock-based compensation expense	248			248
Comprehensive loss	(6,929)				(6,929)
Balance at Dec. 31, 2014	(100,354)	$ 91,554	$ 2	3,402	(103,758)
Balance, shares at Dec. 31, 2014		44,317	1,887
Issuance of common stock upon IPO, net of issuance costs	80,953		$ 5	80,948
Issuance of common stock upon IPO, net of issuance costs, shares			5,294
Conversion of convertible preferred stock to common stock	91,554	$ (91,554)	$ 12	91,542
Conversion of convertible preferred stock to common stock, shares		(44,317)	11,404
Conversion of convertible preferred stock to common stock warrants	648			648
Stock options exercised	$ 323			323
Stock options exercised, shares	209		209
Repurchase of common stock	$ (1)			(1)
Stock-based compensation expense	2,811			2,811
Comprehensive loss	(18,338)				(18,300)	$ (38)
Balance at Dec. 31, 2015	57,596		$ 19	179,673	(122,058)	(38)
Balance, shares at Dec. 31, 2015			18,794
Stock options exercised	$ 234			234
Stock options exercised, shares	78		78
Employee stock purchase plan common stock issuances	$ 548			548
Employee stock purchase plan common stock issuances, shares			36
Stock-based compensation expense	5,915			5,915
Comprehensive loss	(28,848)				(28,730)	(118)
Balance at Dec. 31, 2016	$ 35,445		$ 19	$ 186,370	$ (150,788)	$ (156)
Balance, shares at Dec. 31, 2016			18,908

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net loss	$ (28,730)	$ (18,300)	$ (6,929)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,087	1,005	618
Amortization of debt issuance costs	60	61	59
Amortization of premium on investments	125	425
Accretion of final payment fee on long-term debt	307	307	227
Deferred tax expense	6
Deferred rent	105	6	(13)
Loss (gain) on disposal of equipment	6		(1)
Stock-based compensation	5,915	2,811	248
Changes in fair value of convertible preferred stock warrants		357	80
Changes in operating assets and liabilities, net of acquired assets:
Accrued interest income	172	(247)
Accounts receivables, net	(3,212)	(1,715)	(2,923)
Inventories	(3,337)	(1,450)	(570)
Prepaid expenses and other current assets	123	(808)	(67)
Other non-current assets	(345)	1,683	(1,698)
Accounts payable	596	(206)	1,212
Accrued expenses	6,051	1,913	980
Net cash used in operating activities	(20,071)	(14,158)	(8,777)
Cash flows from investing activities:
Purchase of property and equipment, net of acquired assets	(3,993)	(3,402)	(999)
Proceeds from sale of property and equipment	1		1
XeroGel acquisition	(11,000)
Purchase of investments	(32,182)	(122,677)
Proceeds from maturities of investments	59,439	84,026
Net cash provided by (used in) investing activities	12,265	(42,053)	(998)
Cash flows from financing activities:
Proceeds from long-term debt			5,000
Debt issuance costs			(5)
Proceeds from stock options exercised	234	323	576
Proceeds from common stock issuances from employee stock purchase plan	548
Proceeds from initial public offering, net of issuance costs		80,953
Repurchase of common stock		(1)	(21)
Net cash provided by financing activities	782	81,275	5,550
Effect of exchange rate changes on cash and cash equivalents	(107)
Net (decrease) increase in cash and cash equivalents	(7,131)	25,064	(4,225)
Cash and cash equivalents - beginning of period	28,548	3,484	7,709
Cash and cash equivalents - end of period	21,417	28,548	3,484
Supplemental cash flow information:
Debt issuance costs			5
Cash paid for interest	$ 1,880	$ 1,864	$ 1,349

Organization

Organization	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Organization	NOTE A – ORGANIZATION Nature of Business Entellus Medical, Inc. (the “Company”) was incorporated in Minnesota in April 2006 and was reincorporated in Delaware in August 2006. The Company is focused on delivering superior patient and physician experiences through products designed for the minimally invasive treatment of chronic and recurrent sinusitis in both adult and pediatric patients. The Company’s platform of products provides effective and easy-to-use solutions designed to simplify everything from diagnosis and patient selection, to complex case revisions and post-operative care. The Company’s three core product lines, XprESS™ Multi-Sinus Dilation Systems, MiniFESS™ Surgical Instruments, and FocESS™ Imaging & Navigation, are designed to enable ear, nose and throat (“ENT”) physicians to conveniently and comfortably perform a broad range of procedures in the ENT physician office and simplify operating room-based treatment. The Company currently sells product through its direct sales force in the United States and United Kingdom and in a limited number of additional countries through international distributors. The Company operates in one reporting segment.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	NOTE B – SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Initial Public Offering In February 2015, the Company completed its initial public offering (“IPO”) by issuing 5.3 million shares of common stock at an offering price of $17.00 per share, for net proceeds to the Company of approximately $81.0 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. In connection with the IPO, the Company’s outstanding shares of convertible preferred stock were automatically converted into an aggregate of 11.4 million shares of common stock and warrants exercisable for convertible preferred stock were automatically converted into warrants to purchase up to an aggregate of less than 0.1 million shares of common stock, resulting in the reclassification of the related redeemable convertible preferred stock warrant liability of $0.6 million to additional paid-in-capital. 1-for-4 Reverse Stock Split In connection with the IPO, the Company’s board of directors and stockholders approved a reverse stock split of the Company’s common stock on a 1-for-4 basis. The reverse stock split became effective on January 12, 2015. The par value of the common stock was not adjusted as a result of the reverse stock split. Adjustments corresponding to the reverse stock split were made to the ratio at which the convertible preferred stock converted into common stock immediately prior to the closing of the IPO. Accordingly, all share and per share amounts for all periods presented in these consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the reverse stock split and adjustment of the preferred stock’s conversion ratios. Basis of Preparation The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”). JOBS Act Accounting Election As an emerging growth company under the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”), the Company is eligible to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. The Company has elected to take advantage of the extended transition period for adopting new or revised accounting standards that have different effective dates for public and private companies until such time as those standards apply to private companies. Principles of Consolidation The consolidated financial statements include the accounts of Entellus Medical, Inc., and its wholly owned subsidiary. All significant intercompany transactions and accounts 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 financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates. Foreign Currency Translation Sales and expenses denominated in foreign currencies are translated at average exchange rates in effect throughout the year. Assets and liabilities of foreign operations are translated at period-end exchange rates with the impacts of foreign currency translation recognized to foreign currency translation adjustment, a component of accumulated other comprehensive loss. Foreign currency transaction gains and losses are included in other income (expense) in the consolidated statements of operations and comprehensive loss. Fair Value of Financial Instruments As of December 31, 2016 and 2015, the carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximated their estimated fair value because of the short-term nature of the financial instruments. The Company determines the fair value of its assets and liabilities based on the exchange price that would be received for an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value maximize the use of observable inputs and minimize the use of unobservable inputs. A fair value hierarchy with three levels of inputs, of which the first two are considered observable and the last unobservable, is used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1). The next highest priority is based on quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in non-active markets or other observable inputs (Level 2). The lowest priority is given to unobservable inputs (Level 3). Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an initial maturity of 90 days or less to be cash equivalents. At December 31, 2016 and 2015, cash equivalents consisted of money market funds recorded at fair value and federal and corporate debt securities recorded at amortized costs. There were no investments in marketable securities at December 31, 2016 and $16.7 million were classified as cash equivalents as of December 31, 2015. The Company maintains cash and cash equivalents in bank accounts which, at times, may exceed Federal Deposit Insurance Corporation (“FDIC”) limits. The Company has not experienced any losses from maintaining balances in excess of FDIC limits. Short-Term Investments Short-term investments represent holdings of marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments are classified as available-for-sale and mature within 12 months from the balance sheet date. Investments with maturity dates greater than one year from the balance sheet date are classified as long-term investments. At the time that the maturity dates of these investments become one year or less, the securities are reclassified to short-term investments. The Company’s investments are recorded at fair value, with any unrealized gains and losses reported as a component of stockholders’ equity (deficit) until realized or until a determination is made that an other-than-temporary decline in market value has occurred. The cost of investments sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of interest income or expense. These investments are deemed Level 2 assets under the fair value hierarchy as their fair value is determined under a market approach using valuation models that utilize observable inputs, including maturity date, issue date, settlements date, and current interest rates. Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentrations of credit risk, consist principally of cash equivalents and accounts receivable. The Company generally does not require collateral and losses on accounts receivable have historically been within management’s expectations. The Company’s investment policy limits investments, when held, to certain types of debt securities issued by the U.S. government, its agencies, and institutions with investment-grade credit ratings, as well as corporate debt or commercial paper issued by the highest quality financial and non-financial companies, and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and equivalents and issuers of debt securities to the extent recorded on the consolidated balance sheets. Accounts Receivable Credit is granted to customers in the normal course of business, generally without collateral or any other security to support amounts due. Accounts are considered past due generally after 30 days. The Company maintains an allowance for doubtful accounts for estimated losses in the collection of accounts receivable. The Company makes estimates regarding the future ability of its customers to make required payments based on historical credit experience, delinquency and expected future trends. The Company will write off accounts receivable when it determines that the accounts receivable are uncollectible, typically upon customer bankruptcy or the customer’s non-response to continued collection efforts. The allowance for doubtful accounts was $0.2 million and $0.1 million as of December 31, 2016 and 2015, respectively. The Company also maintains an allowance for sales returns based on historical experience and evaluation of current sales and returns trends. The allowance for sales returns was $0.2 million and $0.3 million as of December 31, 2016 and 2015, respectively. Inventories Inventories are stated at the lower of cost to purchase or manufacture the inventory or the net realizable value of such inventory. Cost is determined using the standard cost method which approximates the first-in, first-out basis. Market value is determined as the lower of replacement cost or net realizable value. The Company regularly reviews inventory quantities in consideration of actual loss experiences, projected future demand, and remaining shelf life to record a provision for excess and obsolete inventory when appropriate. Property and Equipment Property and equipment are recorded at cost. Depreciation of furniture, office, computer and laboratory equipment is calculated on a straight-line basis over the asset’s estimated useful life, which ranges from two to ten years. Tooling and molds are depreciated on a straight-line basis over three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the remaining life of the lease or the useful life of the asset. Repair and maintenance expenditures are charged to earnings as incurred. Major repairs and maintenance expenditures that extend useful lives of property and equipment are capitalized. Deferred Offering Costs Deferred offering costs, primarily consisting of legal, accounting and other direct fees and costs relating to public offerings, are capitalized. As of December 31, 2016, $0.3 million of deferred offering costs were capitalized in other non-current assets on the consolidated balance sheet related to the public offering completed in the first quarter of 2017. As of December 31, 2015, there were no deferred offering costs capitalized. Business Combination On June 29, 2016, the Company acquired and entered into an exclusive license for the XeroGel™ assets with CogENT Therapeutics, LLC for $11.0 million in cash (the “XeroGel acquisition”). T . While the Company uses its best estimates and assumptions as a part of the purchase price allocation process to accurately value assets acquired at the acquisition date, its estimates are inherently uncertain and subject to refinement. (in thousands) Initial Purchase Change Final Purchase Technologies $ 6,000 $ 3,700 $ 9,700 Trade name 350 150 500 Tangible assets 323 — 323 Total identifiable assets 6,673 3,850 10,523 Goodwill $ 4,327 $ (3,850 ) $ 477 The Company may continue to assess and refine the purchase price allocation through the end of the measurement period, which, in accordance with applicable accounting standards, should not exceed one year from the date of the XeroGel acquisition. The intangible assets and goodwill acquired are considered Level 3 financial assets. The Company incurred transaction costs in connection with the acquisition of approximately $0.3 million for the year ended December 31, 2016, which are included in general and administrative expenses. Under the terms of the XeroGel acquisition agreements, the Company became the manufacturer of XeroGel nasal packing material and will continue to market and sell XeroGel nasal packing material to hospitals, offices and ambulatory surgery centers. Prior to the transaction, the Company was the exclusive distributor of XeroGel nasal packing material in the United States. The distribution agreement between the two parties was terminated in connection with the transaction. As a result of the XeroGel acquisition, the Company began recognizing all XeroGel revenue on a gross basis effective June 29, 2016. The Company has concluded that the XeroGel acquisition was not material for purposes of including pro forma information in this report and therefore has not provided any such information herein. Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in a business combination. Intangible assets are recorded at their estimated fair value at the date of acquisition. In the year following the period in which identified intangible assets become fully amortized, the fully amortized balances are removed from the gross asset and accumulated amortization amounts. Goodwill is not amortized, but is instead subject to impairment testing. Intangible assets with finite lives are amortized using a straight-line method over their respective useful lives. Goodwill Impairment Policy The Company chose November 1 to assess its annual goodwill for any impairment in order to closely align with the timing of its annual planning process. he first step of the goodwill impairment test is to perform a qualitative assessment before calculating the fair value of the reporting unit. If based on the qualitative factors, it is more likely than not that the fair value of the reporting unit is less than the carrying amount of the reporting unit, the Company is then required to perform the next step of the goodwill impairment test. The Company has performed a qualitative assessment of the reporting unit and determined that it was not more likely than not that the fair value of the reporting unit was less than the carrying amount of the reporting unit; therefore, the Company was not required to perform the next step of the goodwill impairment test. For the year ended December 31, 2016 no goodwill impairment was identified. The Company did not have any goodwill on its consolidated balance sheet prior to the XeroGel acquisition . Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. The Company has not recorded impairment charges on long-lived assets for the periods presented in these consolidated financial statements. Deferred Rent The Company accounts for rent expense related to operating leases by determining total minimum rent payments on the leases over their respective periods and recognizing the rent expense on a straight-line basis. The difference between the actual amount paid and the amount recorded as rent expense in each period presented is recorded as an adjustment to other non-current liabilities in the consolidated balance sheet. Debt Issuance and Debt Discount Debt issuance costs and discounts are recorded as a reduction of long-term debt. Amortization of debt issuance costs and the debt discount is calculated using the effective interest method over the term of the debt and is recorded in interest expense in the accompanying consolidated statements of operations and comprehensive loss. Revenue Recognition The Company recognizes revenue when persuasive evidence of a sales arrangement exists, delivery of goods has occurred through the transfer of title and risks and rewards of ownership, the selling price is fixed or determinable and collectability is reasonably assured. Revenue is reported net of the allowance for sales returns. Taxes assessed by a governmental authority that are directly imposed on revenue-producing transactions between a seller and a customer are not recorded as revenue. The Company entered into a distribution agreement with CogENT Therapeutics, LLC, (“CogENT”) in September 2013 and was an exclusive distributor of XeroGel nasal packing material in the United States from October 2013 to June 2016. For products shipped from the CogENT warehouse to customers, CogENT was responsible for all manufacturing, order fulfillment, quality and regulatory requirements of the product. For these direct shipment orders, the Company did not take title to CogENT products prior to products being ordered by customers or in the event CogENT products are returned by customers. The Company recorded transactions under this arrangement on a net basis based on the difference between the amounts billed to customers less the amounts paid to CogENT for the XeroGel product. In June 2016, the Company acquired and entered into an exclusive license for the XeroGel assets with CogENT for $11.0 million in cash. Under the terms of the agreements, the Company now manufactures and sells XeroGel nasal packing material to hospitals, offices and ASCs. The distribution agreement between the two parties was terminated in connection with the transaction. As a result of the XeroGel acquisition, the Company began recognizing all XeroGel revenue on a gross basis effective June 29, 2016. The Company’s net revenue from XeroGel sales for the period January 1, 2016 through June 28, 2016 and the years ended December 31, 2015 and 2014 were approximately $0.7 million, $1.2 million and $0.8 million, respectively. The Company records transactions on a gross basis for XeroGel product for which is takes title, ships the product and handles returns. The amounts of revenue recorded on a gross basis from XeroGel sales for the period from January 1, 2016 through June 28, 2016 and the years ended December 31, 2015 and 2014 were approximately $0.1 million, $0.2 million and $0.1 million, respectively. Shipping and Handling Shipping and handling costs charged to customers are included as a component of revenue and related costs are included in costs of goods sold. Cost of Goods Sold Cost of goods sold consists primarily of manufacturing overhead costs, material costs and direct labor. A significant portion of the Company’s cost of goods sold currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment, operations supervision and management, depreciation expense for production equipment, shipping costs and royalty expense payable in connection with sales of certain products. For those products the Company sells as a distributor, cost of goods sold consists primarily of transfer price. Research and Development Costs Research and development expenses consist primarily of engineering, product development, clinical and regulatory affairs, consulting services, materials, depreciation and other costs associated with products and technologies in development. These expenses include employee and non-employee compensation, including stock-based compensation, supplies, materials, consulting, related travel expenses and facility costs. Clinical expenses include clinical trial design, clinical site reimbursement, data management and travel expenses, and the cost of manufacturing products for clinical trials. Expenditures for research and development activities are charged to operations as incurred. Advertising Expense Expenditures for advertising are charged to operations as incurred. Advertising expenses were $1.2 million, $1.1 million and $0.6 million during the years ended December 31, 2016, 2015 and 2014, respectively. Common Stock Valuation and Stock-based Compensation Prior to the IPO, the Company maintained the Entellus Medical, Inc. 2006 Stock Incentive Plan (the “2006 Plan”) to provide long-term incentives for employees, consultants and members of the board of directors. The 2006 Plan allowed for the issuance of non-statutory and incentive stock options to employees and non-statutory stock options to employees, consultants and non-employee directors. In connection with the IPO, the 2006 Plan terminated, and the Company adopted a new equity incentive plan, the Entellus Medical, Inc. 2015 Incentive Award Plan (the “2015 Plan”). The Company is required to determine the fair value of equity incentive awards and recognize compensation expense for all equity incentive awards made to employees and directors, including employee stock options. The Company also determines the fair value of non-statutory stock options issued to consultants based on the fair value of the consultant’s commitment at the date of grant. Such expense is recognized over the requisite service period. In addition, stock-based compensation expense recognized in the consolidated statements of operations and comprehensive loss is based on awards expected to vest; and therefore, the amount of expense has been reduced for estimated forfeitures. The Company uses the straight-line method for expense attribution, except for awards issued with performance-based conditions which require an accelerated attribution method over the requisite performance and service periods. Under the applicable accounting guidance for equity incentive awards issued to non-employees, the date at which the fair value of such awards is measured is equal to the earlier of: 1) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached; or 2) the date at which the counterparty’s performance is complete. The Company recognizes stock-based compensation expense for the fair value of the vested portion of the non-employee awards in the consolidated statements of operations and comprehensive loss. The valuation model used for calculating the fair value of awards for stock-based compensation expense is the Black-Scholes option-pricing model (the “Black-Scholes model”). The Black-Scholes model requires the Company to make assumptions and judgments about the variables used in the calculation, including the expected term (weighted average period of time that the options granted are expected to be outstanding), the volatility of common stock and an assumed risk-free interest rate. The Company uses the “simplified method” to determine the expected term of the stock option. Volatility is based on an average of the historical volatilities of the common stock of publicly-traded companies with characteristics similar to those of the Company. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected term of the option. The expected dividend assumption is based on the Company’s history of not paying dividends and its expectation that it will not declare dividends for the foreseeable future. Potential forfeitures of awards are estimated based on the Company’s historical forfeiture experience. The estimate of forfeitures will be adjusted over the service period to the extent that actual forfeitures differ, or are expected to differ, from prior estimates. Convertible Preferred Stock Warrant Liability For a warrant classified as a derivative liability, the fair value of that warrant is recorded on the consolidated balance sheet when granted and adjusted to fair value at each financial reporting date. The changes in the fair value of the warrants are recorded in the consolidated statements of operations and comprehensive loss as a component of interest income or expense as appropriate. The warrants represent financial instruments that were categorized as Level 3. The Company issued warrants to purchase shares of convertible preferred stock in connection with the Company’s entry into its original credit facility in October 2012. The warrants were recorded at fair value using the Black-Scholes model. The fair value of these warrants was remeasured at each financial reporting period with any changes in fair value being recognized as a component of other income (expense) in the consolidated statements of operations and comprehensive loss. In connection with the IPO, in January 2015, the Company performed the final remeasurement of the warrant liability. There were costs of $0.4 million during the year ended December 31, 2015 recorded as interest expense from the final remeasurement. Upon the closing of the IPO, warrants to purchase shares of convertible preferred stock automatically converted into warrants to purchase shares of common stock. The Company reclassified the warrant liability to additional paid-in capital, as the warrants met the definition of an equity instrument, in the amount of $0.6 million during the year ended December 31, 2015. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company applies a recognition threshold for income tax positions taken or expected to be taken on a tax return. The impact of an uncertain tax position taken or expected to be taken on an income tax return are recognized in the consolidated financial statements at the largest amount that is more-likely-than not to be sustained upon audit by the relevant taxing authority. An uncertain tax position is not recognized in the consolidated financial statements unless it is more-likely-than not of being sustained. The Company has no reserve for unrecognized tax benefits at December 31, 2016 and 2015; and accordingly, there is no interest or penalties recorded on the consolidated balance sheet for such reserves. The Company is currently open to audit under the statute of limitations by the Internal Revenue Service and the appropriate state income taxing authorities for 2006 through 2016. As of December 31, 2016, the Company had a valuation allowance of $51.9 million recorded against its deferred tax assets. The Company a y Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and dilutive potential shares of common stock outstanding during the period. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for those periods as all potentially dilutive shares consisting of convertible preferred stock, stock options and warrants were antidilutive in those periods. The Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. The shares of the Company’s convertible preferred stock participated in any dividends declared by the Company and were therefore considered to be participating securities. Comprehensive Loss Comprehensive loss consists of net loss, changes in unrealized gains and losses on available-for-sale marketable securities and changes in unrealized translation gains and losses. Accumulated other comprehensive income is presented in the accompanying consolidated balance sheets, when applicable. Segment, Geographical and Customer Concentration The Company operates in one segment. No single customer accounted or geographic area for more than 10% of its revenue during the years ended December 31, 2016, 2015 and 2014. Recent Accounting Pronouncements In May 2014, the Financial and Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. This standard will eliminate the transaction and industry specific revenue recognition guidance under current U.S. GAAP and replace it with a principles-based approach for determining revenue recognition. In December 2016, the FASB issued ASU 2016-20, Technical Corrections and Improvements to Topic 606 – Revenue from Contracts with Customers, to clarify the Codification or to correct unintended application of guidance. The new guidance is effective for annual and interim periods beginning after December 15, 2018. ASU 2014-09 allows for full retrospective adoption applied to all periods presented or modified retrospective adoption with the cumulative effect of initially applying the standard recognized at the date of initial application. In March 2016, the FASB issued ASU 2016-08, Principal versus Agent Considerations – Reporting Revenue Gross versus Net. This ASU clarifies the revenue recognition implementation guidance for preparers on certain aspects of principal versus agent consideration. The amendments in this ASU are effective for private companies and emerging growth companies beginning after December 15, 2018. The Company has performed a review of the requirements of the new guidance and has identified which of its revenue streams will be within the scope of ASU 2014-09. The Company is working through an adoption plan which includes a review of customer contracts, applying the five-step model of the new standard, to each revenue stream and comparing the results to its current accounting; an evaluation of the method of adoption; and assessing changes that might be necessary to information technology systems, processes, and internal controls to capture new data and address changes in financial reporting. Because of the nature of the work that remains, at this time the Company is unable to reasonably estimate the impact of adoption on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance, which changes the presentation of debt issuance costs in financial statements. Under ASU 2015-03, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. ASU 2015-03 is effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. A company should apply the new guidance on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Upon transition, a company is required to comply with the applicable disclosures for a change in an accounting principle. The guidance only affects the presentation of debt issuance costs in the balance sheet and has no impact on results of operations. The Company applied ASU 2015-03 on January 1, 2016 and reclassified debt issuance costs from long-term assets to long-term debt. Debt issuance costs included in long-term debt in the accompanying consolidated financial statements were $0.1 million and $0.2 million at December 31, 2016 and December 31, 2015, respectively. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. ASU 2016-01 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The Company does not expect that adoption of ASU 2016-01 will have a significant impact on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases, which requires that lease arrangements longer than twelve months result in an entity recognizing an asset and liability. The updated guidance in this ASU are effective for private companies and emerging growth companies beginning after December 15, 2019. The Company is currently evaluating the imp

Composition of Certain Financia

Composition of Certain Financial Statement Items	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Composition of Certain Financial Statement Items	NOTE C – COMPOSITION OF CERTAIN FINANCIAL STATEMENT ITEMS Inventories December 31, December 31, (in thousands) 2016 2015 Finished goods $ 3,562 $ 1,487 Work in process 536 388 Raw materials 3,128 2,014 Total $ 7,226 $ 3,889 Property and Equipment December 31, December 31, (in thousands) 2016 2015 Furniture and office equipment $ 873 $ 533 Computer hardware and software 2,831 2,187 Laboratory equipment 4,336 2,915 Tooling and molds 1,512 1,243 Leasehold improvements 2,006 583 $ 11,558 $ 7,461 Less accumulated depreciation and amortization (5,465 ) (3,766 ) Property and equipment in progress 394 431 Total $ 6,487 $ 4,126 Depreciation and amortization expense was $1.7 million, $1.0 million and $0.6 million during the years ended December 31, 2016, 2015 and 2014, respectively. Intangible Assets December 31, December 31, (in thousands) 2016 2015 Technologies $ 9,700 $ — Trade name 500 — $ 10,200 $ — Less accumulated amortization (360 ) — Total $ 9,840 $ — In connection with the XeroGel acquisition, the Company acquired the technology-based intangible assets described in the above table and the XeroGel trade name. The technologies are amortized over a useful life of approximately 14 years, based on the remaining useful life of the licenses acquired as management plans to fully utilize the technologies over the full useful life, and the trade name is amortized over a useful life of 14 years. Amortization expense was $0.4 million during the year ended December 31, 2016. Accrued Expenses December 31, December 31, (in thousands) 2016 2015 Compensation and commissions payable $ 8,674 $ 3,898 Royalty payable 1,851 1,800 Other accrued expenses 2,480 1,297 Total $ 13,005 $ 6,995 Interest Expense December 31, December 31, December 31, (in thousands) 2016 2015 2014 Interest expense $ 2,248 $ 2,247 $ 1,750 Increase in fair value of convertible preferred stock warrants — 357 154 Total $ 2,248 $ 2,604 $ 1,904

Liquidity and Business Risks

Liquidity and Business Risks	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Liquidity and Business Risks	NOTE D – LIQUIDITY AND BUSINESS RISKS As of December 31, 2016 and 2015, the Company had cash and cash equivalents of $21.4 million and $28.5 million and an accumulated deficit of $150.8 million and $122.1 million, respectively. In February 2015, the Company completed its IPO by issuing 5.3 million shares of common stock at an offering price of $17.00 per share, for net proceeds to the Company of approximately $81.0 million after deducting underwriting discounts and commissions and offering expenses payable by the Company. In the first quarter of 2017, the Company completed a public offering of shares of its common stock, issuing a total of 2.9 million shares of common stock (including 0.5 million shares issued after exercise by the underwriters of their option to purchase additional shares) at an offering price of $17.00 per share. Certain existing stockholders of the Company also sold approximately 1.2 million shares of common stock in the offering. The Company received estimated net proceeds of approximately $45.4 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. The Company did not receive any proceeds from the sale of shares by the existing selling stockholders. Prior to the public offerings, the Company financed its operations with a combination of revenue, private placements of convertible preferred securities and amounts borrowed under its credit facility. The Company expects that its cash and cash equivalents, short-term investments and anticipated revenue will be sufficient to fund its operations through at least the next twenty-four months from the date of this .

Short-Term Investments

Short-Term Investments	12 Months Ended
	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
SHORT-TERM INVESTMENTS	NOTE E – SHORT-TERM INVESTMENTS The Company determines the appropriate classification of its investments at the time of purchase and revaluates such determinations at each balance sheet date. Marketable securities are classified as held-to-maturity when the Company has the positive intent and ability to hold the securities to maturity. Marketable securities for which the Company does not have the intent or ability to hold to maturity are classified as available-for-sale. Marketable securities classified as available-for-sale are carried at fair market value, with the unrealized gains and losses included in the determination of comprehensive income and reported in stockholders’ equity. The following is a summary of the available-for-sale investments by type of instrument, which are included in short-term investments in the consolidated balance sheet as of December 31, 2016 and December 31, 2015. Unrealized Unrealized Gain in Losses in Accumulated Accumulated Other Other Amortized Comprehensive Comprehensive Estimated December 31, 2016 (in thousands) Cost Loss Loss Fair Value Short-Term Commercial paper $ 2,495 $ 2 $ — $ 2,497 Corporate bonds 4,099 — (2 ) 4,097 Foreign assets 4,250 1 — 4,251 Total available-for-sale securities $ 10,844 $ 3 $ (2 ) $ 10,845 Unrealized Unrealized Gain in Losses in Accumulated Accumulated Other Other Amortized Comprehensive Comprehensive Estimated December 31, 2015 (in thousands) Cost Loss Loss Fair Value Short-Term Commercial paper $ 9,482 $ 10 $ — $ 9,492 Corporate bonds 19,605 — (19 ) 19,586 Government bonds 1,999 — — 1,999 Foreign assets 7,140 — (7 ) 7,133 Total available-for-sale securities $ 38,226 $ 10 $ (26 ) $ 38,210 Based on an evaluation of securities that have been in a loss position, the Company did not recognize any other-than-temporary impairment charges during the years ended December 31, 2016 and December 31, 2015. The Company considered various factors, including a credit and liquidity assessment of the underlying securities and the Company’s intent and ability to hold the underlying securities until the estimated date of recovery of its amortized cost. As of December 31, 2016 and December 31, 2015, available-for-sale maturities as noted in the table above mature in one year or less.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	NOTE F – FAIR VALUE MEASUREMENTS As of December 31, 2016 and 2015, the carrying amounts of cash and cash equivalents, receivables, accounts payable and accrued expenses approximated their estimated fair values because of the short-term nature of these financial instruments. Fair value is defined as the price that would be received upon the sale of an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three categories: • Level 1: Quoted market prices in active markets for identical assets or liabilities. • Level 2: Includes other than Level 1 inputs that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs for which all significant inputs are observable or can be corroborated by observable market data for substantially the full term of the asset or liabilities. • Level 3: Unobservable inputs that are supported by little or no market activities, which would require the Company to develop its own assumptions. Short-term Investments The following is a summary of available-for-sale investments by type of instrument measured at fair value on a recurring basis at December 31, 2016 and December 31, 2015. December 31, 2016 (in thousands) Level 1 Level 2 Level 3 Total Commercial paper $ — $ 2,497 $ — $ 2,497 Corporate bonds — 4,097 — 4,097 Foreign assets — 4,251 — 4,251 Total $ — $ 10,845 $ — $ 10,845 December 31, 2015 (in thousands) Level 1 Level 2 Level 3 Total Commercial paper $ — $ 9,492 $ — $ 9,492 Corporate bonds — 19,586 — 19,586 Government bonds — 1,999 — 1,999 Foreign assets — 7,133 — 7,133 Total $ — $ 38,210 $ — $ 38,210 There were no transfers in or out of Level 1, Level 2 or Level 3 fair value measurement during the years ended December 31, 2016 and December 31, 2015. The Company has not experienced any significant realized gains or losses on its investments in the periods presented in the consolidated statements of operations and comprehensive loss.

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Debt	NOTE G – DEBT The Company has a credit facility (the “credit facility”) with Oxford Finance LLC under the terms of an amended and restated loan and security agreement, which was amended most recently in February 2017. Under the credit facility, the Company can borrow up to a total of $25.0 million in three tranches at a fixed rate of 9.40%. The first tranche of $15.0 million, including the refinance of $7.5 million previously outstanding, was borrowed in December 2013. In connection with the funding of the first tranche, the Company paid a prorated final payment fee on the original credit facility of $0.1 million. The second tranche of up to $5.0 million was available through December 31, 2014, all of which was borrowed during the three months ended December 31, 2014. The third tranche of up to $5.0 million was available at any time through December 31, 2015, subject to certain six-month revenue milestones. Although the specified revenue milestones for the third tranche were achieved, the Company elected not to borrow additional funds. In addition to the principal and interest payments, under the credit facility the Company is required to pay a final payment fee of 7.15% on all amounts outstanding, which is being accrued over the credit facility term and will be due at the earlier of maturity or prepayment. If the Company repays the amounts borrowed under the credit facility prior to maturity, the Company will also be required to pay a prepayment fee equal to 0.75%, with respect to the principal amount that is prepaid. The credit facility includes affirmative and restrictive covenants and events of default, including the following events of default: payment defaults, breaches of covenants, judgment defaults, cross defaults to certain other contracts, certain events with respect to governmental approvals if such events could cause a material adverse change, a material impairment in the perfection or priority of the lender’s security interest or in the value of the collateral, a material adverse change in the business, operations or condition of the Company or any of its subsidiaries and a material impairment of the prospect of repayment of the credit facility. Upon the occurrence of an event of default, a default increase in the interest rate of an additional 5.00% could be applied to the outstanding loan balance and the lender could declare all outstanding obligations immediately due and payable and take such other actions as set forth in the amended and restated loan and security agreement. The Company’s obligations under the credit facility are secured by a first priority security interest in substantially all of its assets, other than its intellectual property. There are no financial covenants contained in the credit facility and the Company is in compliance with the affirmative and restrictive covenants as of December 31, 2016. As of December 31, 2016 and 2015, the Company had $20.0 million of debt outstanding and no unused availability under the credit facility. In connection with the original credit facility and in conjunction with the close of the first tranche in October 2012, the Company issued the lender warrants to purchase 0.2 million shares of Series E Preferred Stock at an exercise price of $1.9594 per share. In connection with the IPO in February 2015, the warrants became exercisable for up to 38 shares of the Company’s common stock with an exercise price of $7.84 per share. Each warrant may be exercised on a cashless basis in whole or in part. Using the Black-Scholes valuation model, management estimated the fair value of these warrants to be approximately $0.1 million at issuance of the warrant. The following assumptions were used to estimate the fair value: expected volatility of 45.00%, risk-free interest rate of 1.64%, and expected term of 10 years. These warrants were considered to be costs incurred as part of the credit facility and were recorded as a debt discount which was offset against the loan, and were to be amortized over the life of the original credit facility based on the effective interest method to interest expense. In connection with one of the amendments to the amended and restated loan and security agreement, the Company amortized the remaining debt discount to interest expense. No stock warrants were issued in conjunction with such amendment. Based on a 22-month amortization period, the Company’s principal payments are due under the amended credit facility as follows for the years ending December 31: (in thousands) 2017 $ 9,118 2018 10,882 $ 20,000 At December 31, 2016 and 2015, the carrying amount of debt approximated fair value because the fixed interest rate approximates current market rates of interest available in the market. The fair value of the Company’s debt is considered a Level 3 measurement.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stockholders' Equity	NOTE H– STOCKHOLDERS’ EQUITY Preferred Stock The Company’s amended and restated certificate of incorporation authorizes 10.0 million shares of preferred stock. As of December 31, 2016 and 2015, no shares of preferred stock were outstanding. Common Stock In May 2014, the Company amended its certificate of incorporation to increase the authorized number of shares of common stock available for issuance from 57.0 million to 57.6 million shares of $0.001 par value common stock. In December 2014, the Company further amended its Certificate of Incorporation to increase the authorized number of shares of common stock available for issuance to 62.3 million shares. In connection with the IPO, the Company further amended and restated its certificate of incorporation to increase the authorized number of shares of common stock available for issuance to 200.0 million shares of common stock. Stockholders are generally entitled to one vote for each share of common stock held on all matters submitted to a vote of the stockholders and do not have any cumulative voting rights. Stockholders are entitled to receive proportionally any dividends declared by the Company’s Board of Directors, subject to any preferential dividend rights of any then outstanding preferred stock. In the event of the Company’s liquidation or dissolution, stockholders are entitled to share ratably in all assets remaining after payment of all debts and other liabilities, subject to any preferential rights of any then outstanding preferred stock. Stockholders have no preemptive, subscription, redemption or conversion rights. 2006 Stock Incentive Plan Under the 2006 Plan approved by the Company’s Board of Directors in August 2006, 3,541,308 shares of common stock were reserved for issuance of incentive stock options (“ISOs”), non-statutory stock options (“NSOs”), stock bonuses and restricted stock to employees, officers, directors and consultants of the Company as of December 31, 2014. ISOs granted under the 2006 Plan generally vest ratably over a four-year vesting term and expire 10 years from the grant date. NSOs vest per the specific agreement and expire 10 years from the date of grant. At December 31, 2014, there were 23 shares available for issuance under the 2006 Plan. In connection with the IPO, the 2006 Plan terminated, and the Company adopted a new equity incentive plan, the 2015 Plan. 2015 Incentive Award Plan In December 2014, the Company’s Board of Directors adopted, and in January 2015, the Company’s stockholders approved, the 2015 Incentive Award Plan (“2015 Plan”). The 2015 Plan became effective on the effective date of the IPO, at which time the Company ceased making awards under the 2006 Plan. Under the 2015 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and certain other awards to individuals who are employees, officers, directors or consultants of the Company. Awards granted under the 2015 Plan generally vest equally over a four-year vesting term and expire 10 years from the grant date. A total of 1,345,570 shares of common stock were initially reserved for issuance under the 2015 Plan. In addition, the number of shares of common stock available for issuance under the 2015 Plan will be annually increased by an amount equal to the lesser of (A) 875,000 shares, (B) 4% of the outstanding shares of the Company’s common stock as of the last day of the Company’s immediately preceding fiscal year or, an amount determined by the Company’s Board of Directors. Furthermore, any shares subject to awards granted under the 2006 Plan which terminate, expire or lapse without the delivery of shares to the holder thereof become available under the 2015 Plan. In the first quarter of 2016, in accordance with this “evergreen” provision, the number of shares available under the 2015 Plan was increased in the amount of approximately 751,750 shares. As of December 31, 2016, 569,968 shares of common stock were available for issuance under the 2015 Plan. A summary of the Company’s stock option activity and related information is as follows: Weighted average Aggregate Weighted remaining intrinsic average contractual value (shares in thousands) Options exercise price term ($000) Balance at December 31, 2013 1,216 $ 1.18 Granted 1,396 10.55 Exercised (466 ) 1.24 Cancelled — — Forfeited (48 ) 2.43 Balance at December 31, 2014 2,098 7.38 Granted 745 21.53 Exercised (209 ) 1.55 Cancelled — — Forfeited (51 ) 14.43 Balance at December 31, 2015 2,583 11.79 Granted 948 16.13 Exercised (78 ) 2.97 Cancelled — — Forfeited (104 ) 17.06 Balance at December 31, 2016 3,349 $ 13.06 7.6 years $ 21,863 Exercisable 1,464 $ 9.97 6.6 years $ 14,008 During the years ended December 31, 2016, 2015 and 2014, the aggregate pre-tax intrinsic value of options exercised was $1.3 million, $3.2 million and $4.2 million, respectively. The aggregate pre-tax intrinsic value was calculated as the difference between the exercise prices of the underlying options and the estimated fair value of the common stock on the date of exercise or December 31, 2016, 2015 and 2014, as applicable. During the years ended December 31, 2016, 2015 and 2014, the fair value of share vesting was $5.2 million, $2.5 million and $0.2 million. The total cash received upon the exercise of options was $0.2 million, $0.3 million and $0.6 million during the years ended December 31, 2016, 2015 and 2014, respectively. During the year ended December 31, 2016, the Company issued time-based restricted stock units (“RSUs”) covering 11,771 shares of common stock that vest equally over four years at a per share weighted average fair value of $16.99. No RSUs vested or were forfeited during the year ended December 31, 2016. During the year ended December 31, 2016, the Company recognized less than $0.1 million of expense related to RSUs. Early Exercise of Stock Options Stock options granted under the 2006 Plan provide option holders the right to elect to exercise unvested options in exchange for restricted common stock. As of December 31, 2013, 41,174 shares remained unvested and subject to a repurchase right held by the Company at the original issuance price in the event the optionees’ service was voluntarily or involuntarily terminated. On October 31, 2014, a director resigned from the Board of Directors of the Company and the Company repurchased the remaining 27,894 unvested shares at a total purchase price of less than $0.1 million in November 2014. Reserved Shares The Company is required to reserve and keep available out of its authorized but unissued shares of common stock a number of shares sufficient to satisfy the exercise of options granted and available for grant under the 2006 Plan and 2015 Plans. The number of such shares of common stock reserved for the exercise and issuance of the following warrants, options, restricted stock units and shares outstanding as of December 31, 2016 and 2015, were as follows: December 31, (in thousands) 2016 2015 Warrants issued in connection with the credit facility 38 38 Restricted stock units 12 — 2006 Stock Incentive Plan, options outstanding 1,770 1,861 2015 Stock Incentive Plan, options outstanding 1,579 723 3,399 2,622 Employee Stock Purchase Plan In December 2014, the Company’s Board of Directors adopted, and in January 2015 the Company’s stockholders approved, the Entellus Medical, Inc. 2015 Employee Stock Purchase Plan (“ESPP”). Under the ESPP, the Company has set two six-month offering periods during each calendar year, one beginning January 1 and ending on June 30, and the other beginning July 1 and ending on December 31, during which employees can choose to have up to 20% of their eligible compensation withheld to purchase less than 2,000 shares of the Company’s common stock during each offering period. The purchase price of the shares is 85% of the market price on the first or last trading day of the offering period, whichever is lower. A total of 200,000 shares of common stock were initially reserved for issuance under the ESPP. In addition, the number of shares of common stock available for issuance under the ESPP will be annually increased on the first day of each fiscal year during the term of the ESPP, beginning with the 2016 fiscal year, by an amount equal to the lesser of (A) 1% of the shares of the Company’s common stock outstanding on the date of the adoption of the plan or (B) a lesser amount determined by the Company’s Board of Directors. In the first quarter of 2016, in accordance with this “evergreen” provision, the number of shares available for grant under the ESPP increased in the amount of 16,488 shares, resulting in a total of 216,488 shares of common stock reserved for issuance under the ESPP. During the year ended December 31, 2016, the Company issued 35,962 shares of its common stock to participants under the ESPP. The Company recognized $0.2 million and zero in stock-based compensation expense related to the ESPP during the years ended December 31, 2016 and December 31, 2015, respectively.

Stock Based Compensation Expens

Stock Based Compensation Expense	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock Based Compensation Expense	NOTE I – STOCK-BASED COMPENSATION EXPENSE Stock-based compensation expense was reflected in the consolidated statement of operations and comprehensive loss for the years ended December 31, 2016, 2015 and 2014, as follows: Years ended December 31, (in thousands) 2016 2015 2014 Cost of goods sold $ 106 $ 65 $ 11 Selling and marketing 2,142 750 111 Research and development 632 260 46 General and administrative 3,035 1,736 80 Total $ 5,915 $ 2,811 $ 248 The amount of unearned stock-based compensation currently estimated to be expensed through the year 2020 related to unvested employee stock-based awards as of December 31, 2016, is approximately $14.1 million. The weighted average period over which the unearned stock-based compensation is expected to be recognized as of December 31, 2016, is approximately 2.5 years. If there are any modifications or cancellations of the underlying unvested securities, the Company may be required to accelerate, increase or cancel any remaining unearned stock-based compensation expense. Future stock-based compensation expense and unearned stock-based compensation will increase to the extent that the Company grants additional stock-based awards. The Company estimates the fair value of stock-based compensation on the date of grant using the Black-Scholes option-pricing model. The Black-Scholes model determines the fair value of stock-based awards based on the fair market value of the Company’s common stock on the date of grant and is affected by assumptions regarding a number of highly complex and subjective variables. These variables include, but are not limited to, the fair market value of the Company’s common stock, volatility over the expected term of the awards and actual and projected employee stock option exercise behaviors. The Company has opted to use the “simplified method” for estimating the expected term of options, whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. Due to the Company’s limited operating history and company-specific historical and implied volatility data, the Company has based its estimate of expected volatility on the blended historical volatility of a group of similar companies that are publicly traded and the Company’s historical volatility. The historical volatility data was computed using the daily closing prices for the selected companies’ shares during the equivalent period of the calculated expected term of the stock-based awards. The Company will continue to analyze the historical stock price volatility and expected term assumptions as more historical data for the Company’s common stock becomes available. The risk-free rate assumption is based on the U.S. Treasury instruments with maturities similar to the expected term of the Company’s stock options. The expected dividend assumption is based on the Company’s history of not paying dividends and its expectation that it will not declare dividends for the foreseeable future. As stock-based compensation expense recognized in the consolidated financial statements is based on awards ultimately expected to vest, it has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from estimates. Forfeitures are estimated based on estimated future employee turnover and historical experience. The fair value of the options granted to employees and directors during the years ended December 31, 2016, 2015 and 2014, was estimated as of the grant date using the Black-Scholes model assuming the weighted average assumptions listed in the following table: Years ended December 31, 2016 2015 2014 Expected life in years 6.1 6.0 5.8 Risk-free interest rate 1.6 % 1.8 % 1.7 % Expected dividend yield 0 % 0 % 0 % Expected volatility 51 % 56 % 54 % Weighted average fair value $ 7.96 $ 11.41 $ 5.32 The fair value of the ESPP options granted to employees during the years ended December 31, 2016, 2015 and 2014, was estimated as of the grant date using the Black-Scholes model assuming the weighted average assumptions listed in the following table: Year ended December 31, 2016 Expected life in years 0.5 Risk-free interest rate 0.4 % Expected dividend yield 0 % Expected volatility 49 % Weighted average fair value $ 5.30 Performance-Based Options Options issued during the year ended December 31, 2014 included grants to certain employees totaling 23 shares that contained vesting conditions contingent on the achievement of certain milestones. Assuming continued service by the employee, the option would vest immediately upon achievement of the performance criteria. At December 31, 2014, certain milestones were achieved and therefore five shares vested immediately. The Company recorded stock-based compensation expense totaling less than $0.1 million related to these options. The remaining 18 shares were cancelled. There were no performance-based option activity for the years ended December 31, 2016 and 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	NOTE J – INCOME TAXES The components of loss before taxes for the years ended December 31, 2016, 2015 and 2014, consist of the following: Years ended December 31, (in thousands) 2016 2015 2014 Domestic $ (28,337 ) $ (17,860 ) $ (6,929 ) Foreign (387 ) (440 ) — Total loss before income taxes $ (28,724 ) $ (18,300 ) $ (6,929 ) Income tax expense differs from the amount computed by applying the statutory federal income tax rate as follows: Years ended December 31, 2016 2015 2014 Tax at statutory federal rate 34.0 % 34.0 % 34.0 % State tax, net of federal benefit 1.9 % 1.8 % 1.1 % Meals and entertainment (1.4 %) (2.0 % ) (4.2 %) Stock-based compensation (1.9 %) (1.9 % ) (0.8 %) Other 0.7 % (0.3 % ) 0.8 % Change in valuation allowance (33.3 %) (31.6 % ) (30.9 %) Total 0 % 0.0 % 0.0 % The tax effects of temporary differences that give rise to significant portions of the net deferred tax asset (liability) were as follows: Years ended December 31, (in thousands) 2016 2015 Deferred tax asset: Accounts receivable $ 110 $ 136 Inventories 112 71 Accrued expenses 363 158 Property and equipment 44 97 Research and development credits generated 1,440 1,091 Net operating loss carryforward 47,883 40,185 Stock-based compensation expense 2,286 780 Other 69 32 Total deferred tax assets 52,307 42,550 Valuation allowance (51,899 ) (42,299 ) Total deferred tax assets, net of valuation allowance 408 251 Deferred tax liabilities: Prepaid expense (395 ) (251 ) Definite-lived intangible assets (13 ) — Goodwill (6 ) — Total deferred tax liabilities (414 ) (251 ) Net deferred tax liabilities $ (6 ) $ — In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will not be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. Based on the level of historical taxable income and projections of future taxable income over the periods in which the deferred tax assets are deductible, management believes that it is more likely than not that the Company will not realize the benefits of these deductible differences. Accordingly, the Company has recorded a valuation allowance against its net deferred tax assets, excluding the indefinite-lived goodwill deferred tax liabilities as of December 31, 2016 and 2015. The Company’s valuation allowance increased by $9.6 million and $5.7 million in 2016 and 2015, respectively, due to the increase in total deferred tax assets. As of December 31, 2016 and 2015, the Company had federal tax net operating loss carryforwards of approximately $138.5 million and $116.4 million, respectively, which will be available to offset earnings during the carryforward period. If not used, these carryforwards begin to expire in 2026. The Company’s research and development credit carryforwards, if not used, begin to expire in 2026. At December 31, 2016, there were $1.6 million of unrecognized deferred tax assets that arose from tax deductions for equity compensation in excess of compensation recognized for financial reporting during years when net operating losses were created. Since the Company has adopted ASU 2016-09 effective January 1, 2017, these deferred tax assets will become recognized but will be subject to a full valuation allowance. As such, there will be no net impact on the financial statements from this adoption. At December 31, 2016 and 2015 the total unrecognized tax benefit was zero. The Company does not believe that its unrecognized tax benefits will significantly change within the next 12 months. The Company’s 2006 to 2016 tax years remain open and subject to examination by the United States. The Company remains subject to possible examination in various other jurisdictions that are not expected to result in material tax adjustments.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Earnings Per Share	NOTE K – EARNINGS PER SHARE Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and dilutive potential shares of common stock outstanding during the period. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for those periods as all potentially dilutive shares consisting of convertible preferred stock, restricted stock units, stock options and warrants were antidilutive in those periods. The following table sets forth the computation of the Company’s net loss per share: Years ended December 31, (in thousands, except per share amounts) 2016 2015 2014 Net loss $ (28,730 ) $ (18,300 ) $ (6,929 ) Weighted average common stock outstanding 18,839 17,217 1,499 Net loss per share, basic and diluted $ (1.53 ) $ (1.06 ) $ (4.62 ) The following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted average shares outstanding because such securities have an antidilutive impact due to losses reported: Years ended December 31, (in thousands, except per share amounts) 2016 2015 2014 Convertible preferred stock outstanding — — 11,404 Convertible preferred stock warrants — — 38 Common stock warrants 38 38 — Common stock options 3,349 2,649 2,098 Common stock RSUs 12 — — Total 3,399 2,687 13,540

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	NOTE L – COMMITMENTS AND CONTINGENCIES License Agreement with Acclarent, Inc. In February 2011, the Company entered into a license agreement with Acclarent, Inc. (“Acclarent”) in connection with the settlement of then-ongoing litigation in which Acclarent alleged that the Company’s FinESS and XprESS products infringed certain claims of five of their patents, which allegations the Company denied. In October 2012, the Company agreed with Acclarent to amend certain terms of the license agreement (as amended, the “Acclarent License”). Pursuant to the Acclarent License, Acclarent granted the Company a worldwide, non-exclusive, royalty-bearing license under certain patents held by Acclarent to manufacture, use and commercialize the Company’s currently marketed XprESS, PathAssist and FinESS products and certain future versions of those products (collectively, the “Covered Products”) in the field of the expansion of paranasal sinuses and sinus pathways. Under the Acclarent License, the Company made an initial up-front, lump-sum payment to Acclarent as a retroactive royalty payment. The Company is also required to pay Acclarent an ongoing royalty in the low double-digit percentages, on a country-by-country basis, on net sales of Covered Products. Royalty expense is included in the costs of goods sold and is recognized in the period when revenue is recognized on Covered Products. The Acclarent License will expire upon the expiration or abandonment of the last to expire of the patents licensed to us under the agreement. Acclarent has the right to terminate the agreement upon 60 days’ notice in the event of the Company’s uncured material breach. Amounts due for royalties payable are recorded within accrued expenses on the consolidated balance sheets. Operating Leases As of December 31, 2016, the Company has three leased facilities under operating lease agreements. The Company entered into a 41-month lease in February 2012, effective April 1, 2012, for its manufacturing facility and corporate headquarters. The Company entered into a 50-month lease on June 30, 2014, effective July 1, 2014, for additional distribution space in a second facility. On February 26, 2015, the Company exercised its right to extend the lease term of its manufacturing facility and corporate headquarters for an additional three years through August 2018. On June 30, 2015, the Company entered into amendments to each lease agreement, among other things, to expand the space occupied by the Company at the property at which the Company’s corporate headquarters are located, and to extend the term of each lease agreement through June 2021, with an option to extend each lease for an additional term through June 2024. Rental payments on operating leases are charged to expense on a straight-line basis over the period of the lease. These lease agreements require the Company to pay executory costs such as real estate taxes, insurance and repairs, and includes renewal and escalation clauses. In connection with the XeroGel acquisition, the Company assumed a lease agreement for manufacturing facility space in Hayward, California through August 31, 2017. Rental payments on operating leases are charged to expense on a straight-line basis over the period of the lease. This lease agreement requires the Company to pay executory costs such, as real estate taxes, insurance and repairs, and includes renewal and escalation clauses. Approximate minimum future obligations which include monthly contractual lease payments under operating leases with initial terms in excess of one year are as follows: (in thousands) 2017 $ 430 2018 395 2019 388 2020 389 2021 197 Total $ 1,799 Total lease expense was approximately $0.6 million, $0.3 million and $0.3 million for the years ended December 31, 2016, 2015 and 2014, respectively. Other Commitments In June 2016, the Company entered into an Amended and Restated Fiagon NA Distribution Agreement with Fiagon NA Corporation in which the Company was granted exclusive distribution rights in the United States and Canada for Fiagon Image Guidance Systems and certain components, parts and related ancillary products i) to hospitals, ii) to ENT physicians in the office, clinic, and surgery centers, and iii) under ENT healthcare system contracts. The terms of the Fiagon Distribution Agreement require the Company to purchase minimum quantities of Fiagon IGS and certain other disposable products through August 9, 2020 in order for the Company to retain exclusive distribution rights.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plan	NOTE M – EMPLOYEE BENEFIT PLAN The Company maintains a tax-qualified 401(k) retirement plan (“401(k) Plan”) for its U.S. employees. Eligible employees may make pre-tax 401(k) contributions under the 401(k) Plan, up to Internal Revenue Code limits. In addition, the Company, in its sole discretion, may make annual matching contributions and/or non-elective employer contributions to the 401(k) Plan. No such discretionary non-elective employer contributions were made during the years ended December 31, 2016, 2015 and 2014 and no such discretionary matching contributions were made during the years ended December 31, 2015 and 2014. During 2016, the Company has accrued for matching contributions that the Company may, in its discretion, make to the 401(k) Plan for the 2016 plan year (ending December 31, 2016) with accruals generally based on a matching contribution for each eligible employee that would be the lesser of: (1) 50% of the eligible employee's 2016 pre-tax 401(k) contributions and (2) 50% of up to 6% the eligible employee's 2016 eligible compensation. The Company’s matching contribution expense during the year ended December 31, 2016 was $0.5 million and zero during the years ended December 31, 2015 and 2014. The Company’s non-elective employer contribution expense was zero during the years ended December 31, 2016, 2015 and 2014. The Company also provides retirement benefits for Entellus Medical Europe, Ltd., employees. Total contributions to retirement plans for Entellus Medical Europe employees were less than $0.1 million in 2016 and in 2015 and zero in 2014.

Segment and Geographical Data

Segment and Geographical Data	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Segment and Geographical Data	NOTE N – SEGMENT AND GEOGRAPHICAL DATA Operating segments are defined as components of an enterprise for which separate discrete financial information is available and evaluated regularly by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company globally manages the business within one reporting segment. Segment information is consistent with how management reviews the business, makes investing and resource allocation decisions and assesses operating performance. Products are sold principally in the United States. The following table represents total revenue by geographic area, based on the location of the customer: Years ended December 31, (in thousands) 2016 2015 2014 United States $ 71,648 $ 60,911 $ 48,820 International 3,536 659 — Total $ 75,184 $ 61,570 $ 48,820 All of the Company’s long-lived assets are located in the United States.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Event	NOTE O – SUBSEQUENT EVENT In the first quarter of 2017, the Company completed a public offering of shares of its common stock, issuing a total of 2.9 million shares of common stock (including 0.5 million shares issued after exercise by the underwriters of their option to purchase additional shares) at an offering price of $17.00 per share. Certain existing stockholders of the Company also sold approximately 1.2 million shares of common stock in the offering. The Company received estimated net proceeds of approximately $45.4 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. The Company did not receive any proceeds from the sale of shares by the existing selling stockholders.

Quarterly Results of Operations

Quarterly Results of Operations	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations	NOTE P – QUARTERLY RESULTS OF OPERATIONS (UNAUDITED) The following is a summary of the Company’s unaudited quarterly results of operations for the years December 31, 2016 and 2015: Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share amounts) 2016 2016 2016 2016 Revenue $ 16,902 $ 18,730 $ 17,880 $ 21,672 Cost of goods sold 4,000 4,459 4,648 5,613 Gross profit 12,902 14,271 13,232 16,059 Operating expenses: Selling and marketing 13,407 13,086 15,364 14,970 Research and development 1,912 1,873 2,047 1,960 General and administrative 3,949 3,838 4,807 5,966 Total operating expense 19,268 18,797 22,218 22,896 Loss from operations (6,366 ) (4,526 ) (8,986 ) (6,837 ) Other income (expense): Interest income 70 83 75 50 Interest expense (562 ) (562 ) (562 ) (562 ) Other non-operating (expense) income (14 ) (16 ) (12 ) 3 Loss before income tax expense (6,872 ) (5,021 ) (9,485 ) (7,346 ) Income tax (expense) benefit — — (34 ) 28 Net loss $ (6,872 ) $ (5,021 ) $ (9,519 ) $ (7,318 ) Net loss per share, basic and diluted $ (0.37 ) $ (0.27 ) $ (0.50 ) $ (0.39 ) Weighted average common shares used to compute net loss per share, basic and diluted 18,801 18,824 18,855 18,876 Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share amounts) 2015 2015 2015 2015 Revenue $ 13,502 $ 15,191 $ 14,804 $ 18,073 Cost of goods sold 2,949 3,348 3,431 4,330 Gross profit 10,553 11,843 11,373 13,743 Operating expenses: Selling and marketing 9,887 9,815 12,308 12,937 Research and development 1,300 1,308 1,392 1,387 General and administrative 2,816 3,074 3,230 3,914 Total operating expense 14,003 14,197 16,930 18,238 Loss from operations (3,450 ) (2,354 ) (5,557 ) (4,495 ) Other income (expense): Interest income 21 50 47 53 Interest expense (919 ) (562 ) (561 ) (562 ) Other non-operating expense — (2 ) — (9 ) Total other expense, net (898 ) (514 ) (514 ) (518 ) Net loss $ (4,348 ) $ (2,868 ) $ (6,071 ) $ (5,013 ) Net loss per share, basic and diluted $ (0.35 ) $ (0.15 ) $ (0.32 ) $ (0.27 ) Weighted average common shares used to compute net loss per share, basic and diluted 12,542 18,718 18,738 18,784

Schedule II - Valuation and Qua

Schedule II - Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation And Qualifying Accounts [Abstract]
Schedule II - Valuation and Qualifying Accounts	SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS Beginning Ending (in thousands) Balance Additions Deductions Balance Allowance for doubtful accounts receivable Year ended December 31, 2016 $ 135 $ 34 $ 19 $ 150 Year ended December 31, 2015 150 46 61 135 Year ended December 31, 2014 135 49 34 150 Reserve for sales returns and allowances Year ended December 31, 2016 $ 251 $ 66 $ 159 $ 158 Year ended December 31, 2015 140 230 119 251 Year ended December 31, 2014 100 120 80 140

Summary of Significant Accoun24

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Initial Public Offering	Initial Public Offering In February 2015, the Company completed its initial public offering (“IPO”) by issuing 5.3 million shares of common stock at an offering price of $17.00 per share, for net proceeds to the Company of approximately $81.0 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. In connection with the IPO, the Company’s outstanding shares of convertible preferred stock were automatically converted into an aggregate of 11.4 million shares of common stock and warrants exercisable for convertible preferred stock were automatically converted into warrants to purchase up to an aggregate of less than 0.1 million shares of common stock, resulting in the reclassification of the related redeemable convertible preferred stock warrant liability of $0.6 million to additional paid-in-capital.
1-for-4 Reverse Stock Split	1-for-4 Reverse Stock Split In connection with the IPO, the Company’s board of directors and stockholders approved a reverse stock split of the Company’s common stock on a 1-for-4 basis. The reverse stock split became effective on January 12, 2015. The par value of the common stock was not adjusted as a result of the reverse stock split. Adjustments corresponding to the reverse stock split were made to the ratio at which the convertible preferred stock converted into common stock immediately prior to the closing of the IPO. Accordingly, all share and per share amounts for all periods presented in these consolidated financial statements and notes thereto have been adjusted retroactively, where applicable, to reflect the reverse stock split and adjustment of the preferred stock’s conversion ratios.
Basis of Preparation	Basis of Preparation The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”).
JOBS Act Accounting Election	JOBS Act Accounting Election As an emerging growth company under the Jumpstart Our Business Startups Act of 2012 (“JOBS Act”), the Company is eligible to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. The Company has elected to take advantage of the extended transition period for adopting new or revised accounting standards that have different effective dates for public and private companies until such time as those standards apply to private companies.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Entellus Medical, Inc., and its wholly owned subsidiary. All significant intercompany transactions and accounts 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 financial statements and the reported amounts of revenue and expenses during the reporting period. Actual results could differ from those estimates.
Foreign Currency Translation	Foreign Currency Translation Sales and expenses denominated in foreign currencies are translated at average exchange rates in effect throughout the year. Assets and liabilities of foreign operations are translated at period-end exchange rates with the impacts of foreign currency translation recognized to foreign currency translation adjustment, a component of accumulated other comprehensive loss. Foreign currency transaction gains and losses are included in other income (expense) in the consolidated statements of operations and comprehensive loss.
Fair Value of Financial Instruments	Fair Value of Financial Instruments As of December 31, 2016 and 2015, the carrying amounts of cash and cash equivalents, accounts receivable, accounts payable and accrued expenses approximated their estimated fair value because of the short-term nature of the financial instruments. The Company determines the fair value of its assets and liabilities based on the exchange price that would be received for an asset or paid to transfer a liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value maximize the use of observable inputs and minimize the use of unobservable inputs. A fair value hierarchy with three levels of inputs, of which the first two are considered observable and the last unobservable, is used to measure fair value. The fair value hierarchy gives the highest priority to quoted prices in active markets for identical assets or liabilities (Level 1). The next highest priority is based on quoted prices for similar assets or liabilities in active markets or quoted prices for identical or similar assets or liabilities in non-active markets or other observable inputs (Level 2). The lowest priority is given to unobservable inputs (Level 3).
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an initial maturity of 90 days or less to be cash equivalents. At December 31, 2016 and 2015, cash equivalents consisted of money market funds recorded at fair value and federal and corporate debt securities recorded at amortized costs. There were no investments in marketable securities at December 31, 2016 and $16.7 million were classified as cash equivalents as of December 31, 2015. The Company maintains cash and cash equivalents in bank accounts which, at times, may exceed Federal Deposit Insurance Corporation (“FDIC”) limits. The Company has not experienced any losses from maintaining balances in excess of FDIC limits.
Short-Term Investments	Short-Term Investments Short-term investments represent holdings of marketable securities in accordance with the Company’s investment policy and cash management strategy. Short-term investments are classified as available-for-sale and mature within 12 months from the balance sheet date. Investments with maturity dates greater than one year from the balance sheet date are classified as long-term investments. At the time that the maturity dates of these investments become one year or less, the securities are reclassified to short-term investments. The Company’s investments are recorded at fair value, with any unrealized gains and losses reported as a component of stockholders’ equity (deficit) until realized or until a determination is made that an other-than-temporary decline in market value has occurred. The cost of investments sold is determined based on the specific identification method and any realized gains or losses on the sale of investments are reflected as a component of interest income or expense. These investments are deemed Level 2 assets under the fair value hierarchy as their fair value is determined under a market approach using valuation models that utilize observable inputs, including maturity date, issue date, settlements date, and current interest rates.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to concentrations of credit risk, consist principally of cash equivalents and accounts receivable. The Company generally does not require collateral and losses on accounts receivable have historically been within management’s expectations. The Company’s investment policy limits investments, when held, to certain types of debt securities issued by the U.S. government, its agencies, and institutions with investment-grade credit ratings, as well as corporate debt or commercial paper issued by the highest quality financial and non-financial companies, and places restrictions on maturities and concentration by type and issuer. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash and equivalents and issuers of debt securities to the extent recorded on the consolidated balance sheets.
Accounts Receivable	Accounts Receivable Credit is granted to customers in the normal course of business, generally without collateral or any other security to support amounts due. Accounts are considered past due generally after 30 days. The Company maintains an allowance for doubtful accounts for estimated losses in the collection of accounts receivable. The Company makes estimates regarding the future ability of its customers to make required payments based on historical credit experience, delinquency and expected future trends. The Company will write off accounts receivable when it determines that the accounts receivable are uncollectible, typically upon customer bankruptcy or the customer’s non-response to continued collection efforts. The allowance for doubtful accounts was $0.2 million and $0.1 million as of December 31, 2016 and 2015, respectively. The Company also maintains an allowance for sales returns based on historical experience and evaluation of current sales and returns trends. The allowance for sales returns was $0.2 million and $0.3 million as of December 31, 2016 and 2015, respectively.
Inventories	Inventories Inventories are stated at the lower of cost to purchase or manufacture the inventory or the net realizable value of such inventory. Cost is determined using the standard cost method which approximates the first-in, first-out basis. Market value is determined as the lower of replacement cost or net realizable value. The Company regularly reviews inventory quantities in consideration of actual loss experiences, projected future demand, and remaining shelf life to record a provision for excess and obsolete inventory when appropriate.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Depreciation of furniture, office, computer and laboratory equipment is calculated on a straight-line basis over the asset’s estimated useful life, which ranges from two to ten years. Tooling and molds are depreciated on a straight-line basis over three to five years. Leasehold improvements are amortized on a straight-line basis over the shorter of the remaining life of the lease or the useful life of the asset. Repair and maintenance expenditures are charged to earnings as incurred. Major repairs and maintenance expenditures that extend useful lives of property and equipment are capitalized.
Deferred Offering Costs	Deferred Offering Costs Deferred offering costs, primarily consisting of legal, accounting and other direct fees and costs relating to public offerings, are capitalized. As of December 31, 2016, $0.3 million of deferred offering costs were capitalized in other non-current assets on the consolidated balance sheet related to the public offering completed in the first quarter of 2017. As of December 31, 2015, there were no deferred offering costs capitalized.
Business Combination	Business Combination On June 29, 2016, the Company acquired and entered into an exclusive license for the XeroGel™ assets with CogENT Therapeutics, LLC for $11.0 million in cash (the “XeroGel acquisition”). T . While the Company uses its best estimates and assumptions as a part of the purchase price allocation process to accurately value assets acquired at the acquisition date, its estimates are inherently uncertain and subject to refinement. (in thousands) Initial Purchase Change Final Purchase Technologies $ 6,000 $ 3,700 $ 9,700 Trade name 350 150 500 Tangible assets 323 — 323 Total identifiable assets 6,673 3,850 10,523 Goodwill $ 4,327 $ (3,850 ) $ 477 The Company may continue to assess and refine the purchase price allocation through the end of the measurement period, which, in accordance with applicable accounting standards, should not exceed one year from the date of the XeroGel acquisition. The intangible assets and goodwill acquired are considered Level 3 financial assets. The Company incurred transaction costs in connection with the acquisition of approximately $0.3 million for the year ended December 31, 2016, which are included in general and administrative expenses. Under the terms of the XeroGel acquisition agreements, the Company became the manufacturer of XeroGel nasal packing material and will continue to market and sell XeroGel nasal packing material to hospitals, offices and ambulatory surgery centers. Prior to the transaction, the Company was the exclusive distributor of XeroGel nasal packing material in the United States. The distribution agreement between the two parties was terminated in connection with the transaction. As a result of the XeroGel acquisition, the Company began recognizing all XeroGel revenue on a gross basis effective June 29, 2016. The Company has concluded that the XeroGel acquisition was not material for purposes of including pro forma information in this report and therefore has not provided any such information herein.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the fair value of net assets acquired in a business combination. Intangible assets are recorded at their estimated fair value at the date of acquisition. In the year following the period in which identified intangible assets become fully amortized, the fully amortized balances are removed from the gross asset and accumulated amortization amounts. Goodwill is not amortized, but is instead subject to impairment testing. Intangible assets with finite lives are amortized using a straight-line method over their respective useful lives.
Goodwill Impairment Policy	Goodwill Impairment Policy The Company chose November 1 to assess its annual goodwill for any impairment in order to closely align with the timing of its annual planning process. he first step of the goodwill impairment test is to perform a qualitative assessment before calculating the fair value of the reporting unit. If based on the qualitative factors, it is more likely than not that the fair value of the reporting unit is less than the carrying amount of the reporting unit, the Company is then required to perform the next step of the goodwill impairment test. The Company has performed a qualitative assessment of the reporting unit and determined that it was not more likely than not that the fair value of the reporting unit was less than the carrying amount of the reporting unit; therefore, the Company was not required to perform the next step of the goodwill impairment test. For the year ended December 31, 2016 no goodwill impairment was identified. The Company did not have any goodwill on its consolidated balance sheet prior to the XeroGel acquisition .
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to future undiscounted net cash flows expected to be generated by the asset. If such assets are considered to be impaired, the impairment to be recognized is measured by the amount by which the carrying amount of the assets exceed the fair value of the assets. Assets to be disposed of are reported at the lower of the carrying amount or fair value less costs to sell. The Company has not recorded impairment charges on long-lived assets for the periods presented in these consolidated financial statements.
Deferred Rent	Deferred Rent The Company accounts for rent expense related to operating leases by determining total minimum rent payments on the leases over their respective periods and recognizing the rent expense on a straight-line basis. The difference between the actual amount paid and the amount recorded as rent expense in each period presented is recorded as an adjustment to other non-current liabilities in the consolidated balance sheet.
Debt Issuance and Debt Discount	Debt Issuance and Debt Discount Debt issuance costs and discounts are recorded as a reduction of long-term debt. Amortization of debt issuance costs and the debt discount is calculated using the effective interest method over the term of the debt and is recorded in interest expense in the accompanying consolidated statements of operations and comprehensive loss.
Revenue Recognition	Revenue Recognition The Company recognizes revenue when persuasive evidence of a sales arrangement exists, delivery of goods has occurred through the transfer of title and risks and rewards of ownership, the selling price is fixed or determinable and collectability is reasonably assured. Revenue is reported net of the allowance for sales returns. Taxes assessed by a governmental authority that are directly imposed on revenue-producing transactions between a seller and a customer are not recorded as revenue. The Company entered into a distribution agreement with CogENT Therapeutics, LLC, (“CogENT”) in September 2013 and was an exclusive distributor of XeroGel nasal packing material in the United States from October 2013 to June 2016. For products shipped from the CogENT warehouse to customers, CogENT was responsible for all manufacturing, order fulfillment, quality and regulatory requirements of the product. For these direct shipment orders, the Company did not take title to CogENT products prior to products being ordered by customers or in the event CogENT products are returned by customers. The Company recorded transactions under this arrangement on a net basis based on the difference between the amounts billed to customers less the amounts paid to CogENT for the XeroGel product. In June 2016, the Company acquired and entered into an exclusive license for the XeroGel assets with CogENT for $11.0 million in cash. Under the terms of the agreements, the Company now manufactures and sells XeroGel nasal packing material to hospitals, offices and ASCs. The distribution agreement between the two parties was terminated in connection with the transaction. As a result of the XeroGel acquisition, the Company began recognizing all XeroGel revenue on a gross basis effective June 29, 2016. The Company’s net revenue from XeroGel sales for the period January 1, 2016 through June 28, 2016 and the years ended December 31, 2015 and 2014 were approximately $0.7 million, $1.2 million and $0.8 million, respectively. The Company records transactions on a gross basis for XeroGel product for which is takes title, ships the product and handles returns. The amounts of revenue recorded on a gross basis from XeroGel sales for the period from January 1, 2016 through June 28, 2016 and the years ended December 31, 2015 and 2014 were approximately $0.1 million, $0.2 million and $0.1 million, respectively.
Shipping and Handling	Shipping and Handling Shipping and handling costs charged to customers are included as a component of revenue and related costs are included in costs of goods sold.
Cost of Goods Sold	Cost of Goods Sold Cost of goods sold consists primarily of manufacturing overhead costs, material costs and direct labor. A significant portion of the Company’s cost of goods sold currently consists of manufacturing overhead costs. These overhead costs include the cost of quality assurance, material procurement, inventory control, facilities, equipment, operations supervision and management, depreciation expense for production equipment, shipping costs and royalty expense payable in connection with sales of certain products. For those products the Company sells as a distributor, cost of goods sold consists primarily of transfer price.
Research and Development Costs	Research and Development Costs Research and development expenses consist primarily of engineering, product development, clinical and regulatory affairs, consulting services, materials, depreciation and other costs associated with products and technologies in development. These expenses include employee and non-employee compensation, including stock-based compensation, supplies, materials, consulting, related travel expenses and facility costs. Clinical expenses include clinical trial design, clinical site reimbursement, data management and travel expenses, and the cost of manufacturing products for clinical trials. Expenditures for research and development activities are charged to operations as incurred.
Advertising Expense	Advertising Expense Expenditures for advertising are charged to operations as incurred. Advertising expenses were $1.2 million, $1.1 million and $0.6 million during the years ended December 31, 2016, 2015 and 2014, respectively.
Common Stock Valuation and Stock-based Compensation	Common Stock Valuation and Stock-based Compensation Prior to the IPO, the Company maintained the Entellus Medical, Inc. 2006 Stock Incentive Plan (the “2006 Plan”) to provide long-term incentives for employees, consultants and members of the board of directors. The 2006 Plan allowed for the issuance of non-statutory and incentive stock options to employees and non-statutory stock options to employees, consultants and non-employee directors. In connection with the IPO, the 2006 Plan terminated, and the Company adopted a new equity incentive plan, the Entellus Medical, Inc. 2015 Incentive Award Plan (the “2015 Plan”). The Company is required to determine the fair value of equity incentive awards and recognize compensation expense for all equity incentive awards made to employees and directors, including employee stock options. The Company also determines the fair value of non-statutory stock options issued to consultants based on the fair value of the consultant’s commitment at the date of grant. Such expense is recognized over the requisite service period. In addition, stock-based compensation expense recognized in the consolidated statements of operations and comprehensive loss is based on awards expected to vest; and therefore, the amount of expense has been reduced for estimated forfeitures. The Company uses the straight-line method for expense attribution, except for awards issued with performance-based conditions which require an accelerated attribution method over the requisite performance and service periods. Under the applicable accounting guidance for equity incentive awards issued to non-employees, the date at which the fair value of such awards is measured is equal to the earlier of: 1) the date at which a commitment for performance by the counterparty to earn the equity instrument is reached; or 2) the date at which the counterparty’s performance is complete. The Company recognizes stock-based compensation expense for the fair value of the vested portion of the non-employee awards in the consolidated statements of operations and comprehensive loss. The valuation model used for calculating the fair value of awards for stock-based compensation expense is the Black-Scholes option-pricing model (the “Black-Scholes model”). The Black-Scholes model requires the Company to make assumptions and judgments about the variables used in the calculation, including the expected term (weighted average period of time that the options granted are expected to be outstanding), the volatility of common stock and an assumed risk-free interest rate. The Company uses the “simplified method” to determine the expected term of the stock option. Volatility is based on an average of the historical volatilities of the common stock of publicly-traded companies with characteristics similar to those of the Company. The risk-free rate is based on the U.S. Treasury yield curve in effect at the time of grant for periods corresponding with the expected term of the option. The expected dividend assumption is based on the Company’s history of not paying dividends and its expectation that it will not declare dividends for the foreseeable future. Potential forfeitures of awards are estimated based on the Company’s historical forfeiture experience. The estimate of forfeitures will be adjusted over the service period to the extent that actual forfeitures differ, or are expected to differ, from prior estimates.
Convertible Preferred Stock Warrant Liability	Convertible Preferred Stock Warrant Liability For a warrant classified as a derivative liability, the fair value of that warrant is recorded on the consolidated balance sheet when granted and adjusted to fair value at each financial reporting date. The changes in the fair value of the warrants are recorded in the consolidated statements of operations and comprehensive loss as a component of interest income or expense as appropriate. The warrants represent financial instruments that were categorized as Level 3. The Company issued warrants to purchase shares of convertible preferred stock in connection with the Company’s entry into its original credit facility in October 2012. The warrants were recorded at fair value using the Black-Scholes model. The fair value of these warrants was remeasured at each financial reporting period with any changes in fair value being recognized as a component of other income (expense) in the consolidated statements of operations and comprehensive loss. In connection with the IPO, in January 2015, the Company performed the final remeasurement of the warrant liability. There were costs of $0.4 million during the year ended December 31, 2015 recorded as interest expense from the final remeasurement. Upon the closing of the IPO, warrants to purchase shares of convertible preferred stock automatically converted into warrants to purchase shares of common stock. The Company reclassified the warrant liability to additional paid-in capital, as the warrants met the definition of an equity instrument, in the amount of $0.6 million during the year ended December 31, 2015.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax base and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The Company applies a recognition threshold for income tax positions taken or expected to be taken on a tax return. The impact of an uncertain tax position taken or expected to be taken on an income tax return are recognized in the consolidated financial statements at the largest amount that is more-likely-than not to be sustained upon audit by the relevant taxing authority. An uncertain tax position is not recognized in the consolidated financial statements unless it is more-likely-than not of being sustained. The Company has no reserve for unrecognized tax benefits at December 31, 2016 and 2015; and accordingly, there is no interest or penalties recorded on the consolidated balance sheet for such reserves. The Company is currently open to audit under the statute of limitations by the Internal Revenue Service and the appropriate state income taxing authorities for 2006 through 2016. As of December 31, 2016, the Company had a valuation allowance of $51.9 million recorded against its deferred tax assets. The Company a y
Net Loss Per Share	Net Loss per Share Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and dilutive potential shares of common stock outstanding during the period. Because the Company has reported a net loss for all periods presented, diluted net loss per share is the same as basic net loss per share for those periods as all potentially dilutive shares consisting of convertible preferred stock, stock options and warrants were antidilutive in those periods. The Company allocates no loss to participating securities because they have no contractual obligation to share in the losses of the Company. The shares of the Company’s convertible preferred stock participated in any dividends declared by the Company and were therefore considered to be participating securities.
Comprehensive Loss	Comprehensive Loss Comprehensive loss consists of net loss, changes in unrealized gains and losses on available-for-sale marketable securities and changes in unrealized translation gains and losses. Accumulated other comprehensive income is presented in the accompanying consolidated balance sheets, when applicable.
Segment Geographical and Customer Concentration	Segment, Geographical and Customer Concentration The Company operates in one segment. No single customer accounted or geographic area for more than 10% of its revenue during the years ended December 31, 2016, 2015 and 2014.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial and Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers. This standard will eliminate the transaction and industry specific revenue recognition guidance under current U.S. GAAP and replace it with a principles-based approach for determining revenue recognition. In December 2016, the FASB issued ASU 2016-20, Technical Corrections and Improvements to Topic 606 – Revenue from Contracts with Customers, to clarify the Codification or to correct unintended application of guidance. The new guidance is effective for annual and interim periods beginning after December 15, 2018. ASU 2014-09 allows for full retrospective adoption applied to all periods presented or modified retrospective adoption with the cumulative effect of initially applying the standard recognized at the date of initial application. In March 2016, the FASB issued ASU 2016-08, Principal versus Agent Considerations – Reporting Revenue Gross versus Net. This ASU clarifies the revenue recognition implementation guidance for preparers on certain aspects of principal versus agent consideration. The amendments in this ASU are effective for private companies and emerging growth companies beginning after December 15, 2018. The Company has performed a review of the requirements of the new guidance and has identified which of its revenue streams will be within the scope of ASU 2014-09. The Company is working through an adoption plan which includes a review of customer contracts, applying the five-step model of the new standard, to each revenue stream and comparing the results to its current accounting; an evaluation of the method of adoption; and assessing changes that might be necessary to information technology systems, processes, and internal controls to capture new data and address changes in financial reporting. Because of the nature of the work that remains, at this time the Company is unable to reasonably estimate the impact of adoption on its consolidated financial statements. In April 2015, the FASB issued ASU 2015-03, Simplifying the Presentation of Debt Issuance, which changes the presentation of debt issuance costs in financial statements. Under ASU 2015-03, an entity presents such costs in the balance sheet as a direct deduction from the related debt liability rather than as an asset. Amortization of the costs is reported as interest expense. ASU 2015-03 is effective for fiscal years and interim periods within those fiscal years, beginning after December 15, 2015. Early adoption is permitted for financial statements that have not been previously issued. A company should apply the new guidance on a retrospective basis, wherein the balance sheet of each individual period presented should be adjusted to reflect the period-specific effects of applying the new guidance. Upon transition, a company is required to comply with the applicable disclosures for a change in an accounting principle. The guidance only affects the presentation of debt issuance costs in the balance sheet and has no impact on results of operations. The Company applied ASU 2015-03 on January 1, 2016 and reclassified debt issuance costs from long-term assets to long-term debt. Debt issuance costs included in long-term debt in the accompanying consolidated financial statements were $0.1 million and $0.2 million at December 31, 2016 and December 31, 2015, respectively. In January 2016, the FASB issued ASU 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities, which addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. ASU 2016-01 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The Company does not expect that adoption of ASU 2016-01 will have a significant impact on its consolidated financial statements. In February 2016, the FASB issued ASU 2016-02, Leases, which requires that lease arrangements longer than twelve months result in an entity recognizing an asset and liability. The updated guidance in this ASU are effective for private companies and emerging growth companies beginning after December 15, 2019. The Company is currently evaluating the impact of the updated guidance on its consolidated financial statements. In March 2016, the FASB issued ASU 2016-09, Compensation – Stock Compensation, which is intended to simplify several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, the estimation of forfeitures, shares withheld for taxes and classification of shares withheld for taxes on the statement of cash flows. As part of the adoption of this guidance the Company has elected to account for forfeitures of share-based awards as they occur. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses to require the measurement of expected credit losses for financial instruments held at the reporting date based on historical experience, current conditions and reasonable forecasts. The main objective of this ASU is to provide financial statement users with more decision-useful information about the expected credit losses on financial instruments and other commitments to extend credit held by a reporting entity at each reporting date. This ASU is effective for private companies and emerging growth companies beginning after December 15, 2020; the ASU allows for early adoption as of the beginning of an interim or annual reporting period beginning after December 15, 2018. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. In August 2016, the FASB issued ASU 2016-15, Statements of Cash Flows – Classifications of Certain Cash Receipts and Cash Payments to clarify how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This ASU is effective for private companies and emerging growth companies beginning after December 15, 2018; the ASU allows for early adoption. The Company does not believe that adoption of ASU 2016-15 will have a significant impact on its consolidated financial statements. In January 2017, the FASB issued ASU 2017-01, Business Combinations – Clarifying the Definition of a Business, to clarify the definition of a business with the objective of adding guidance to assist entities with evaluating whether transactions should be accounted for as acquisitions (or dispositions) of assets or businesses. This ASU is effective for private companies and emerging growth companies beginning after December 15, 2018, the ASU allows for early adoption. The Company does not believe that adoption of ASU 2017-01 will have a significant impact on its consolidated financial statements.

Summary of Significant Accoun25

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of Adjustments to Assets Acquired	As a result, during the measurement period, the Company has recorded adjustments to the assets acquired as follows: (in thousands) Initial Purchase Change Final Purchase Technologies $ 6,000 $ 3,700 $ 9,700 Trade name 350 150 500 Tangible assets 323 — 323 Total identifiable assets 6,673 3,850 10,523 Goodwill $ 4,327 $ (3,850 ) $ 477

Composition of Certain Financ26

Composition of Certain Financial Statement Items (Tables)	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Inventories	Inventories December 31, December 31, (in thousands) 2016 2015 Finished goods $ 3,562 $ 1,487 Work in process 536 388 Raw materials 3,128 2,014 Total $ 7,226 $ 3,889
Schedule of Property and Equipment	Property and Equipment December 31, December 31, (in thousands) 2016 2015 Furniture and office equipment $ 873 $ 533 Computer hardware and software 2,831 2,187 Laboratory equipment 4,336 2,915 Tooling and molds 1,512 1,243 Leasehold improvements 2,006 583 $ 11,558 $ 7,461 Less accumulated depreciation and amortization (5,465 ) (3,766 ) Property and equipment in progress 394 431 Total $ 6,487 $ 4,126
Schedule of Intangible Assets	Intangible Assets December 31, December 31, (in thousands) 2016 2015 Technologies $ 9,700 $ — Trade name 500 — $ 10,200 $ — Less accumulated amortization (360 ) — Total $ 9,840 $ —
Schedule of Accrued Expenses	Accrued Expenses December 31, December 31, (in thousands) 2016 2015 Compensation and commissions payable $ 8,674 $ 3,898 Royalty payable 1,851 1,800 Other accrued expenses 2,480 1,297 Total $ 13,005 $ 6,995
Schedule of Interest Expense	Interest Expense December 31, December 31, December 31, (in thousands) 2016 2015 2014 Interest expense $ 2,248 $ 2,247 $ 1,750 Increase in fair value of convertible preferred stock warrants — 357 154 Total $ 2,248 $ 2,604 $ 1,904

Short-Term Investments (Tables)

Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Summary of Investments by Type of Instrument	The following is a summary of the available-for-sale investments by type of instrument, which are included in short-term investments in the consolidated balance sheet as of December 31, 2016 and December 31, 2015. Unrealized Unrealized Gain in Losses in Accumulated Accumulated Other Other Amortized Comprehensive Comprehensive Estimated December 31, 2016 (in thousands) Cost Loss Loss Fair Value Short-Term Commercial paper $ 2,495 $ 2 $ — $ 2,497 Corporate bonds 4,099 — (2 ) 4,097 Foreign assets 4,250 1 — 4,251 Total available-for-sale securities $ 10,844 $ 3 $ (2 ) $ 10,845 Unrealized Unrealized Gain in Losses in Accumulated Accumulated Other Other Amortized Comprehensive Comprehensive Estimated December 31, 2015 (in thousands) Cost Loss Loss Fair Value Short-Term Commercial paper $ 9,482 $ 10 $ — $ 9,492 Corporate bonds 19,605 — (19 ) 19,586 Government bonds 1,999 — — 1,999 Foreign assets 7,140 — (7 ) 7,133 Total available-for-sale securities $ 38,226 $ 10 $ (26 ) $ 38,210

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Summary of Available-for-sale Investments at Fair Value on Recurring Basis	The following is a summary of available-for-sale investments by type of instrument measured at fair value on a recurring basis at December 31, 2016 and December 31, 2015. December 31, 2016 (in thousands) Level 1 Level 2 Level 3 Total Commercial paper $ — $ 2,497 $ — $ 2,497 Corporate bonds — 4,097 — 4,097 Foreign assets — 4,251 — 4,251 Total $ — $ 10,845 $ — $ 10,845 December 31, 2015 (in thousands) Level 1 Level 2 Level 3 Total Commercial paper $ — $ 9,492 $ — $ 9,492 Corporate bonds — 19,586 — 19,586 Government bonds — 1,999 — 1,999 Foreign assets — 7,133 — 7,133 Total $ — $ 38,210 $ — $ 38,210

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Principal Payments due under Amended Credit Facility	Based on a 22-month amortization period, the Company’s principal payments are due under the amended credit facility as follows for the years ending December 31: (in thousands) 2017 $ 9,118 2018 10,882 $ 20,000

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock Option Activity and Related Information	A summary of the Company’s stock option activity and related information is as follows: Weighted average Aggregate Weighted remaining intrinsic average contractual value (shares in thousands) Options exercise price term ($000) Balance at December 31, 2013 1,216 $ 1.18 Granted 1,396 10.55 Exercised (466 ) 1.24 Cancelled — — Forfeited (48 ) 2.43 Balance at December 31, 2014 2,098 7.38 Granted 745 21.53 Exercised (209 ) 1.55 Cancelled — — Forfeited (51 ) 14.43 Balance at December 31, 2015 2,583 11.79 Granted 948 16.13 Exercised (78 ) 2.97 Cancelled — — Forfeited (104 ) 17.06 Balance at December 31, 2016 3,349 $ 13.06 7.6 years $ 21,863 Exercisable 1,464 $ 9.97 6.6 years $ 14,008
Summary of Common Stock Reserved for Exercise and Issuance of Warrants, Options, Restricted Stock Units and Shares Outstanding	The number of such shares of common stock reserved for the exercise and issuance of the following warrants, options, restricted stock units and shares outstanding as of December 31, 2016 and 2015, were as follows: December 31, (in thousands) 2016 2015 Warrants issued in connection with the credit facility 38 38 Restricted stock units 12 — 2006 Stock Incentive Plan, options outstanding 1,770 1,861 2015 Stock Incentive Plan, options outstanding 1,579 723 3,399 2,622

Stock Based Compensation Expe31

Stock Based Compensation Expense (Tables)	12 Months Ended
	Dec. 31, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Stock-based Compensation Expense in Consolidated Statement of Operations and Comprehensive Loss	Stock-based compensation expense was reflected in the consolidated statement of operations and comprehensive loss for the years ended December 31, 2016, 2015 and 2014, as follows: Years ended December 31, (in thousands) 2016 2015 2014 Cost of goods sold $ 106 $ 65 $ 11 Selling and marketing 2,142 750 111 Research and development 632 260 46 General and administrative 3,035 1,736 80 Total $ 5,915 $ 2,811 $ 248
Summary of Weighted Average Assumptions Used in Black-Scholes Model in Estimating Fair Value of Option Granted	The fair value of the options granted to employees and directors during the years ended December 31, 2016, 2015 and 2014, was estimated as of the grant date using the Black-Scholes model assuming the weighted average assumptions listed in the following table: Years ended December 31, 2016 2015 2014 Expected life in years 6.1 6.0 5.8 Risk-free interest rate 1.6 % 1.8 % 1.7 % Expected dividend yield 0 % 0 % 0 % Expected volatility 51 % 56 % 54 % Weighted average fair value $ 7.96 $ 11.41 $ 5.32
Summary of Weighted Average Assumptions Used in Black-Scholes Model in Estimating Fair Value of ESPP Option Granted	The fair value of the ESPP options granted to employees during the years ended December 31, 2016, 2015 and 2014, was estimated as of the grant date using the Black-Scholes model assuming the weighted average assumptions listed in the following table: Year ended December 31, 2016 Expected life in years 0.5 Risk-free interest rate 0.4 % Expected dividend yield 0 % Expected volatility 49 % Weighted average fair value $ 5.30

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Components of Loss Before Taxes	The components of loss before taxes for the years ended December 31, 2016, 2015 and 2014, consist of the following: Years ended December 31, (in thousands) 2016 2015 2014 Domestic $ (28,337 ) $ (17,860 ) $ (6,929 ) Foreign (387 ) (440 ) — Total loss before income taxes $ (28,724 ) $ (18,300 ) $ (6,929 )
Reconciliation of Federal Statutory to Effective Income Tax Rate	Income tax expense differs from the amount computed by applying the statutory federal income tax rate as follows: Years ended December 31, 2016 2015 2014 Tax at statutory federal rate 34.0 % 34.0 % 34.0 % State tax, net of federal benefit 1.9 % 1.8 % 1.1 % Meals and entertainment (1.4 %) (2.0 % ) (4.2 %) Stock-based compensation (1.9 %) (1.9 % ) (0.8 %) Other 0.7 % (0.3 % ) 0.8 % Change in valuation allowance (33.3 %) (31.6 % ) (30.9 %) Total 0 % 0.0 % 0.0 %
Schedule of Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to significant portions of the net deferred tax asset (liability) were as follows: Years ended December 31, (in thousands) 2016 2015 Deferred tax asset: Accounts receivable $ 110 $ 136 Inventories 112 71 Accrued expenses 363 158 Property and equipment 44 97 Research and development credits generated 1,440 1,091 Net operating loss carryforward 47,883 40,185 Stock-based compensation expense 2,286 780 Other 69 32 Total deferred tax assets 52,307 42,550 Valuation allowance (51,899 ) (42,299 ) Total deferred tax assets, net of valuation allowance 408 251 Deferred tax liabilities: Prepaid expense (395 ) (251 ) Definite-lived intangible assets (13 ) — Goodwill (6 ) — Total deferred tax liabilities (414 ) (251 ) Net deferred tax liabilities $ (6 ) $ —

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of Net Loss Per Share	The following table sets forth the computation of the Company’s net loss per share: Years ended December 31, (in thousands, except per share amounts) 2016 2015 2014 Net loss $ (28,730 ) $ (18,300 ) $ (6,929 ) Weighted average common stock outstanding 18,839 17,217 1,499 Net loss per share, basic and diluted $ (1.53 ) $ (1.06 ) $ (4.62 )
Schedule of Antidilutive Securities Outstanding Excluded from Computation of Diluted Weighted Average Shares Outstanding	The following potentially dilutive securities outstanding have been excluded from the computations of diluted weighted average shares outstanding because such securities have an antidilutive impact due to losses reported: Years ended December 31, (in thousands, except per share amounts) 2016 2015 2014 Convertible preferred stock outstanding — — 11,404 Convertible preferred stock warrants — — 38 Common stock warrants 38 38 — Common stock options 3,349 2,649 2,098 Common stock RSUs 12 — — Total 3,399 2,687 13,540

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments And Contingencies Disclosure [Abstract]
Summary of Annual Future Minimum Lease Payments	Approximate minimum future obligations which include monthly contractual lease payments under operating leases with initial terms in excess of one year are as follows: (in thousands) 2017 $ 430 2018 395 2019 388 2020 389 2021 197 Total $ 1,799

Segment and Geographical Data (

Segment and Geographical Data (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Revenue by Geographical Area, Based on the Location of Customer	The following table represents total revenue by geographic area, based on the location of the customer: Years ended December 31, (in thousands) 2016 2015 2014 United States $ 71,648 $ 60,911 $ 48,820 International 3,536 659 — Total $ 75,184 $ 61,570 $ 48,820

Quarterly Results of Operatio36

Quarterly Results of Operations (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results of Operations	The following is a summary of the Company’s unaudited quarterly results of operations for the years December 31, 2016 and 2015: Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share amounts) 2016 2016 2016 2016 Revenue $ 16,902 $ 18,730 $ 17,880 $ 21,672 Cost of goods sold 4,000 4,459 4,648 5,613 Gross profit 12,902 14,271 13,232 16,059 Operating expenses: Selling and marketing 13,407 13,086 15,364 14,970 Research and development 1,912 1,873 2,047 1,960 General and administrative 3,949 3,838 4,807 5,966 Total operating expense 19,268 18,797 22,218 22,896 Loss from operations (6,366 ) (4,526 ) (8,986 ) (6,837 ) Other income (expense): Interest income 70 83 75 50 Interest expense (562 ) (562 ) (562 ) (562 ) Other non-operating (expense) income (14 ) (16 ) (12 ) 3 Loss before income tax expense (6,872 ) (5,021 ) (9,485 ) (7,346 ) Income tax (expense) benefit — — (34 ) 28 Net loss $ (6,872 ) $ (5,021 ) $ (9,519 ) $ (7,318 ) Net loss per share, basic and diluted $ (0.37 ) $ (0.27 ) $ (0.50 ) $ (0.39 ) Weighted average common shares used to compute net loss per share, basic and diluted 18,801 18,824 18,855 18,876 Three Months Ended March 31, June 30, September 30, December 31, (in thousands, except per share amounts) 2015 2015 2015 2015 Revenue $ 13,502 $ 15,191 $ 14,804 $ 18,073 Cost of goods sold 2,949 3,348 3,431 4,330 Gross profit 10,553 11,843 11,373 13,743 Operating expenses: Selling and marketing 9,887 9,815 12,308 12,937 Research and development 1,300 1,308 1,392 1,387 General and administrative 2,816 3,074 3,230 3,914 Total operating expense 14,003 14,197 16,930 18,238 Loss from operations (3,450 ) (2,354 ) (5,557 ) (4,495 ) Other income (expense): Interest income 21 50 47 53 Interest expense (919 ) (562 ) (561 ) (562 ) Other non-operating expense — (2 ) — (9 ) Total other expense, net (898 ) (514 ) (514 ) (518 ) Net loss $ (4,348 ) $ (2,868 ) $ (6,071 ) $ (5,013 ) Net loss per share, basic and diluted $ (0.35 ) $ (0.15 ) $ (0.32 ) $ (0.27 ) Weighted average common shares used to compute net loss per share, basic and diluted 12,542 18,718 18,738 18,784

Organization - Additional Infor

Organization - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of reportable segments	1

Summary of Significant Accoun38

Summary of Significant Accounting Policies - Additional Information (Detail)	Jun. 29, 2016USD ($)	Jan. 12, 2015	Feb. 28, 2015USD ($)$ / sharesshares	Jun. 28, 2016USD ($)	Dec. 31, 2016USD ($)SegmentCustomer	Dec. 31, 2015USD ($)Customer	Dec. 31, 2014USD ($)Customer	Jun. 30, 2016USD ($)
Accounting Policies [Line Items]
Proceeds from initial public offering, net of issuance costs						$ 80,953,000
Reverse stock split conversion ratio		0.25
Period for considering accounts receivable as past due					30 days
Allowance for doubtful accounts receivable					$ 200,000	100,000
Allowance for sales returns					200,000	300,000
Deferred offering costs					300,000	0
Payments to acquire business in cash					11,000,000
Goodwill impairment					0
Goodwill				$ 0	477,000
Advertising expense					1,200,000	1,100,000	$ 600,000
Changes in fair value of convertible preferred stock warrants						357,000	$ 80,000
Reserve for unrecognized tax benefits					0	0
Interest or penalties on unrecognized tax benefits					0	0
Deferred tax assets, valuation allowance					51,899,000	$ 42,299,000
Loss allocated to participating securities					$ 0
Number of operating segment | Segment					1
Number of customers accounted or geographic area for more than 10% of revenue | Customer					0	0	0
Debt issuance costs					$ 116,000	$ 176,000
Interest Expense [Member]
Accounting Policies [Line Items]
Changes in fair value of convertible preferred stock warrants						400,000
CogENT Therapeutics, LLC [Member]
Accounting Policies [Line Items]
Payments to acquire business in cash	$ 11,000,000
Business acquisition, transaction costs					300,000
Goodwill					477,000			$ 4,327,000
Net revenue				700,000		1,200,000	$ 800,000
Gross revenue				$ 100,000		200,000	$ 100,000
Cash and Cash Equivalents [Member]
Accounting Policies [Line Items]
Investment in marketable securities					$ 0	16,700,000
Maximum [Member] | Furniture and Office Equipment [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					10 years
Maximum [Member] | Computer Hardware and Software [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					10 years
Maximum [Member] | Laboratory Equipment [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					10 years
Maximum [Member] | Tooling and Molds [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					5 years
Minimum [Member] | Furniture and Office Equipment [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					2 years
Minimum [Member] | Computer Hardware and Software [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					2 years
Minimum [Member] | Laboratory Equipment [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					2 years
Minimum [Member] | Tooling and Molds [Member]
Accounting Policies [Line Items]
Estimated useful life of property and equipment					3 years
Initial Public Offering [Member]
Accounting Policies [Line Items]
Common stock, shares issued | shares			5,300,000
Common stock offering price per share | $ / shares			$ 17
Proceeds from initial public offering, net of issuance costs			$ 81,000,000
Number of common stock converted from preferred stock | shares			11,400,000
Preferred stock warrant liability reclassified			$ 600,000			$ 600,000
Initial Public Offering [Member] | Maximum [Member]
Accounting Policies [Line Items]
Shares purchasable upon conversion of preferred stock | shares			100,000

Summary of Significant Accoun39

Summary of Significant Accounting Policies - Schedule of Adjustments to Assets Acquired (Detail) - USD ($)	6 Months Ended
	Dec. 31, 2016	Jun. 30, 2016	Jun. 28, 2016
Initial Purchase Price Allocation
Goodwill	$ 477,000		$ 0
CogENT Therapeutics, LLC [Member]
Initial Purchase Price Allocation
Tangible assets	323,000	$ 323,000
Total identifiable assets	10,523,000	6,673,000
Goodwill	477,000	4,327,000
Change
Total identifiable assets	3,850,000
Goodwill	(3,850,000)
CogENT Therapeutics, LLC [Member] | Technologies [Member]
Initial Purchase Price Allocation
Intangible assets	9,700,000	6,000,000
Change
Intangible assets	3,700,000
CogENT Therapeutics, LLC [Member] | Trade Name [Member]
Initial Purchase Price Allocation
Intangible assets	500,000	$ 350,000
Change
Intangible assets	$ 150,000

Composition of Certain Financ40

Composition of Certain Financial Statement Items - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Finished goods	$ 3,562	$ 1,487
Work in process	536	388
Raw materials	3,128	2,014
Total	$ 7,226	$ 3,889

Composition of Certain Financ41

Composition of Certain Financial Statement Items - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	$ 11,558	$ 7,461
Less accumulated depreciation and amortization	(5,465)	(3,766)
Property and equipment in progress	394	431
Total	6,487	4,126
Furniture and Office Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	873	533
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	2,831	2,187
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	4,336	2,915
Tooling and Molds [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	1,512	1,243
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, Gross	$ 2,006	$ 583

Composition of Certain Financ42

Composition of Certain Financial Statement Items - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Finite Lived Intangible Assets [Line Items]
Depreciation and amortization of fixed assets	$ 1.7	$ 1	$ 0.6
Amortization expenses	$ 0.4
Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Useful life of Intangible asset	14 years
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Useful life of Intangible asset	14 years

Composition of Certain Financ43

Composition of Certain Financial Statement Items - Schedule of Intangible Assets (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 10,200
Less accumulated amortization	(360)
Total	9,840
Technologies [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	9,700
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 500

Composition of Certain Financ44

Composition of Certain Financial Statement Items - Schedule of Accrued Expenses (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Compensation and commissions payable	$ 8,674	$ 3,898
Royalty payable	1,851	1,800
Other accrued expenses	2,480	1,297
Accrued expenses, Total	$ 13,005	$ 6,995

Composition of Certain Financ45

Composition of Certain Financial Statement Items - Schedule of Interest Expense (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Interest Expenses [Line Items]
Interest expense									$ 2,248	$ 2,247	$ 1,750
Increase in fair value of convertible preferred stock warrants										357	80
Interest expense, Total	$ 562	$ 562	$ 562	$ 562	$ 562	$ 561	$ 562	$ 919	$ 2,248	2,604	1,904
Convertible Preferred Stock [Member]
Schedule Of Interest Expenses [Line Items]
Increase in fair value of convertible preferred stock warrants										$ 357	$ 154

Liquidity and Business Risks -

Liquidity and Business Risks - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2015	Mar. 31, 2017	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2013
Subsidiary, Sale of Stock [Line Items]
Cash and cash equivalents			$ 28,548,000	$ 21,417,000	$ 3,484,000	$ 7,709,000
Accumulated deficit			122,058,000	$ 150,788,000
Proceeds from initial public offering, net of issuance costs			$ 80,953,000
Initial Public Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued	5.3
Common stock offering price per share	$ 17
Proceeds from initial public offering, net of issuance costs	$ 81,000,000
Secondary Public Offering [Member] | Scenario Forecast [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued		2.9
Common stock offering price per share		$ 17
Proceeds from issuance of common stock, net of issuance costs		$ 45,400,000
Additional Share Purchase by Underwriters [Member] | Scenario Forecast [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock, shares issued		0.5
Sale by Certain Existing Shareholders [Member] | Scenario Forecast [Member]
Subsidiary, Sale of Stock [Line Items]
Common stock sold by certain existing stockholders		1.2
Proceeds from sale of shares by existing selling stockholders		$ 0

Short-term Investments - Summar

Short-term Investments - Summary of Investments by Type of Instrument (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 10,844	$ 38,226
Unrealized Gain in Accumulated Other Comprehensive Loss	3	10
Unrealized Losses in Accumulated Other Comprehensive Loss	(2)	(26)
Estimated Fair Value	10,845	38,210
Short-term Investments [Member] | Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,495	9,482
Unrealized Gain in Accumulated Other Comprehensive Loss	2	10
Estimated Fair Value	2,497	9,492
Short-term Investments [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,099	19,605
Unrealized Losses in Accumulated Other Comprehensive Loss	(2)	(19)
Estimated Fair Value	4,097	19,586
Short-term Investments [Member] | Foreign Assets [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	4,250	7,140
Unrealized Gain in Accumulated Other Comprehensive Loss	1
Unrealized Losses in Accumulated Other Comprehensive Loss		(7)
Estimated Fair Value	$ 4,251	7,133
Short-term Investments [Member] | Government Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		1,999
Estimated Fair Value		$ 1,999

Short-term Investments - Additi

Short-term Investments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Other-than-temporary impairment charges	$ 0	$ 0

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Available-for-sale Investments at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	$ 10,845	$ 38,210
Fair Value, Measurements, Recurring [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	10,845	38,210
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	10,845	38,210
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	2,497	9,492
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member] | Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	2,497	9,492
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	4,097	19,586
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	4,097	19,586
Fair Value, Measurements, Recurring [Member] | Foreign Assets [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	4,251	7,133
Fair Value, Measurements, Recurring [Member] | Foreign Assets [Member] | Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments	$ 4,251	7,133
Fair Value, Measurements, Recurring [Member] | Government Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments		1,999
Fair Value, Measurements, Recurring [Member] | Government Bonds [Member] | Level 2 [Member]
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale investments		$ 1,999

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Transfer of assets between level 1, level 2 or level 3	$ 0	$ 0

Debt - Additional Information (

Debt - Additional Information (Detail)	Apr. 01, 2017USD ($)Payment	Mar. 15, 2017USD ($)	Feb. 28, 2017USD ($)Tranches	Dec. 31, 2013USD ($)	Oct. 31, 2012$ / sharesshares	Dec. 31, 2016USD ($)shares	Dec. 31, 2015USD ($)	Feb. 28, 2015$ / sharesshares	Dec. 31, 2014USD ($)
Debt Instrument [Line Items]
Line of credit facility, amount outstanding						$ 20,000,000
Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding						$ 20,000,000	$ 20,000,000
Maturity date of debt instrument						Dec. 1, 2018
Credit facility final payment fee						7.15%
Default increase in additional interest rate				5.00%
Line of credit facility, unused available amount						$ 0	0
Exercise price of warrants | $ / shares								$ 7.84
Estimated fair value of warrants						$ 100,000
Expected volatility						45.00%
Risk-free interest rate						1.64%
Expected life in years						10 years
Stock warrants issued in conjunction with amended facility | shares						0
Credit Facility [Member] | Series E Preferred Stock [Member]
Debt Instrument [Line Items]
Issuance of warrants to purchase stock | shares					200,000
Exercise price of warrants | $ / shares					$ 1.9594
Credit Facility [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding				$ 15,000,000
Payment fee				100,000
Credit Facility [Member] | Third Tranche [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity							$ 5,000,000
Credit Facility [Member] | Prior to First Anniversary
Debt Instrument [Line Items]
Credit facility prepayment fee						0.75%
Credit Facility [Member] | Scenario Forecast [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 25,000,000
Fixed interest floor rate			9.40%
Number of tranches | Tranches			3
Maturity date of debt instrument			Mar. 15, 2017
Credit facility, first installment payments of principal and interest	$ 1,000,000	$ 1,800,000
Number of equal monthly payments of principal and interest | Payment	21
Credit Facility [Member] | Scenario, Previously Reported [Member] | First Tranche [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding				$ 7,500,000
Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Warrant exercisable in connection with IPO | shares								38,000
Credit Facility [Member] | Maximum [Member] | Second Tranche [Member]
Debt Instrument [Line Items]
Line of credit facility, amount outstanding									$ 5,000,000

Debt - Schedule of Principal Pa

Debt - Schedule of Principal Payments due under Amended Credit Facility (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Long Term Debt By Maturity [Abstract]
2,017	$ 9,118
2,018	10,882
Total principal payments	$ 20,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)	Nov. 30, 2014	Jan. 31, 2015	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	May 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock, shares authorized				10,000,000	10,000,000
Preferred stock, shares outstanding				0	0
Common stock, shares authorized				200,000,000	200,000,000	62,300,000	57,000,000	57,600,000
Common stock, par value				$ 0.001	$ 0.001	$ 0.001
Common stock reserved for issuance				3,399,000	2,622,000
Common stock available for issuance				3,349,000	2,583,000	2,098,000	1,216,000
Stock-based compensation				$ 5,915,000	$ 2,811,000	$ 248,000
Unvested and subject to a repurchase, shares							41,174
Repurchase of common stock, shares	27,894
Repurchase of common stock					1,000	$ 21,000
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance		200,000	216,488
Annual increase in shares available for grant			16,488
Weighted average fair value				$ 5.30
Stock-based compensation				$ 200,000	$ 0
Increase in share reserve as percentage of shares of Common Stock outstanding on plan adoption date				1.00%
First offering date				Jan. 1, 2016
Stock issued during period shares				35,962
Maximum percentage of compensation employees can withheld				20.00%
Purchase price as a percentage of market price				85.00%
Employee Stock Purchase Plan, Plan Description				Under the ESPP, the Company has set two six-month offering periods during each calendar year, one beginning January 1 and ending on June 30, and the other beginning July 1 and ending on December 31, during which employees can choose to have up to 20% of their eligible compensation withheld to purchase less than 2,000 shares of the Company’s common stock during each offering period. The purchase price of the shares is 85% of the market price on the first or last trading day of the offering period, whichever is lower.
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock	$ 100,000
Maximum [Member] | Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued during period shares				2,000
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance				12,000
2006 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						3,541,308
Option available for future grant						23
2006 Stock Incentive Plan [Member] | Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term						4 years
Expiry period for option granted						10 years
2006 Stock Incentive Plan [Member] | Non-Statutory Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiry period for option granted						10 years
2015 Incentive Award Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance		1,345,570		1,579,000	723,000
Annual increase in shares available for grant		875,000	751,750
Annual percentage increase in shares available for grant		4.00%
Common stock available for issuance				569,968
Aggregate pre-tax intrinsic value of options exercised				$ 1,300,000	$ 3,200,000	$ 4,200,000
Fair value of options vested				5,200,000	2,500,000	200,000
Total cash received upon the exercise of options				$ 200,000	$ 300,000	$ 600,000
2015 Incentive Award Plan [Member] | Incentive Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term					4 years
Expiry period for option granted					10 years
2015 Incentive Award Plan [Member] | Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting term				4 years
Restricted shares issued				11,771
Weighted average fair value				$ 16.99
Shares vested				0
Shares forfeited				0
2015 Incentive Award Plan [Member] | Restricted Stock Units [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation				$ 100,000

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, Beginning balance	2,583	2,098	1,216
Options Granted	948	745	1,396
Options Exercised	(78)	(209)	(466)
Options Forfeited	(104)	(51)	(48)
Options outstanding, Ending balance	3,349	2,583	2,098
Options Exercisable, Ending balance	1,464
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Beginning balance	$ 11.79	$ 7.38	$ 1.18
Weighted Average Exercise Price, Granted	16.13	21.53	10.55
Weighted Average Exercise Price, Exercised	2.97	1.55	1.24
Weighted Average Exercise Price, Forfeited	17.06	14.43	2.43
Weighted Average Exercise Price, Ending balance	13.06	$ 11.79	$ 7.38
Weighted Average Exercise Price, Exercisable	$ 9.97
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Term	7 years 7 months 6 days
Weighted Average Remaining Contractual Term, Exercisable	6 years 7 months 6 days
Aggregate Intrinsic Value	$ 21,863
Aggregate Intrinsic Value Exercisable	$ 14,008

Stockholders' Equity - Summar55

Stockholders' Equity - Summary of Common Stock Reserved for Exercise and Issuance of Warrants, Options, Restricted Stock Units and Shares Outstanding (Detail) - shares	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2015
Class Of Stock [Line Items]
Common stock reserved for exercise and issuance	3,399,000	2,622,000
2006 Equity Incentive Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for exercise and issuance	1,770,000	1,861,000
2015 Stock Incentive Plan [Member]
Class Of Stock [Line Items]
Common stock reserved for exercise and issuance	1,579,000	723,000	1,345,570
Restricted Stock Units [Member]
Class Of Stock [Line Items]
Common stock reserved for exercise and issuance	12,000
Credit Facility [Member]
Class Of Stock [Line Items]
Common stock reserved for exercise and issuance	38,000	38,000

Stock Based Compensation Expe56

Stock Based Compensation Expense - Summary of Stock-Based Compensation Expense in Consolidated Statement of Operations and Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 5,915	$ 2,811	$ 248
Cost of Goods Sold [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	106	65	11
Selling and Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,142	750	111
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	632	260	46
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,035	$ 1,736	$ 80

Stock Based Compensation Expe57

Stock Based Compensation Expense - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested employee stock-based award	$ 14,100,000
Options Granted	948,000	745,000	1,396,000
Stock-based compensation expense	$ 5,915,000	$ 2,811,000	$ 248,000
Number of employees stock options, cancelled	104,000	51,000	48,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for unearned stock-based compensation expense	2 years 6 months
Performance-Based Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Granted	0	0	23,000
Number of employees stock options, vested			5,000
Number of employees stock options, cancelled			18,000
Performance-Based Options [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 100,000

Stock Based Compensation Expe58

Stock Based Compensation Expense - Summary of Weighted Average Assumptions Used in Black-Scholes Model in Estimating Fair Value of Option Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years	6 months
Risk-free interest rate	0.40%
Expected dividend yield	0.00%
Expected volatility	49.00%
Weighted average fair value	$ 5.30
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life in years	6 years 1 month 6 days	6 years	5 years 9 months 18 days
Risk-free interest rate	1.60%	1.80%	1.70%
Expected dividend yield	0.00%	0.00%	0.00%
Expected volatility	51.00%	56.00%	54.00%
Weighted average fair value	$ 7.96	$ 11.41	$ 5.32

Income Taxes - Schedule of Comp

Income Taxes - Schedule of Components of Loss Before Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Domestic					$ (28,337)	$ (17,860)	$ (6,929)
Foreign					(387)	(440)
Loss before income tax expense	$ (7,346)	$ (9,485)	$ (5,021)	$ (6,872)	$ (28,724)	$ (18,300)	$ (6,929)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Federal Statutory to Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Tax at statutory federal rate	34.00%	34.00%	34.00%
State tax, net of federal benefit	1.90%	1.80%	1.10%
Meals and entertainment	(1.40%)	(2.00%)	(4.20%)
Stock-based compensation	(1.90%)	(1.90%)	(0.80%)
Other	0.70%	(0.30%)	0.80%
Change in valuation allowance	(33.30%)	(31.60%)	(30.90%)
Total	0.00%	0.00%	0.00%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax asset:
Accounts receivable	$ 110	$ 136
Inventories	112	71
Accrued expenses	363	158
Property and equipment	44	97
Research and development credits generated	1,440	1,091
Net operating loss carryforward	47,883	40,185
Stock-based compensation expense	2,286	780
Other	69	32
Total deferred tax assets	52,307	42,550
Valuation allowance	(51,899)	(42,299)
Total deferred tax assets, net of valuation allowance	408	251
Deferred tax liabilities:
Prepaid expense	(395)	(251)
Definite-lived intangible assets	(13)
Goodwill	(6)
Total deferred tax liabilities	(414)	$ (251)
Net deferred tax liabilities	$ (6)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Increase in valuation allowance, deferred tax assets	$ 9,600,000	$ 5,700,000
Unrecognized deferred tax assets	1,600,000
Total unrecognized tax benefits	$ 0	0
Earliest Tax Year [Member]
Income Taxes [Line Items]
Open tax year	2,006
Latest Tax Year [Member]
Income Taxes [Line Items]
Open tax year	2,016
Research and Development Credit Carryforwards [Member]
Income Taxes [Line Items]
Tax credit carryforwards expiration year	2,026
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 138,500,000	$ 116,400,000
Net operating loss carryforwards expiration year	2,026

Earnings Per Share - Schedule o

Earnings Per Share - Schedule of Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (7,318)	$ (9,519)	$ (5,021)	$ (6,872)	$ (5,013)	$ (6,071)	$ (2,868)	$ (4,348)	$ (28,730)	$ (18,300)	$ (6,929)
Weighted average common stock outstanding	18,876	18,855	18,824	18,801	18,784	18,738	18,718	12,542	18,839	17,217	1,499
Net loss per share, basic and diluted	$ (0.39)	$ (0.50)	$ (0.27)	$ (0.37)	$ (0.27)	$ (0.32)	$ (0.15)	$ (0.35)	$ (1.53)	$ (1.06)	$ (4.62)

Earnings Per Share - Schedule64

Earnings Per Share - Schedule of Antidilutive Securities Outstanding Excluded from Computation of Diluted Weighted Average Shares Outstanding (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding	3,399	2,687	13,540
Convertible Preferred Stock Outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding			11,404
Convertible Preferred Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding			38
Common Stock Warrants [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding	38	38
Common Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding	3,349	2,649	2,098
Common Stock RSUs [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive potential common shares excluded from computation of diluted weighted average shares outstanding	12

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Feb. 26, 2015	Jun. 30, 2014	Feb. 29, 2012	Dec. 31, 2016USD ($)Facilities	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Commitments And Contingencies Disclosure [Abstract]
Number of leased facilities under operating lease agreement | Facilities				3
Operating leased facility, period		50 months	41 months
Operating leased facility, effective date		Jul. 1, 2014	Apr. 1, 2012
Operating leased facility, additional period	3 years
Operating leased facility, amendment description				On June 30, 2015, the Company entered into amendments to each lease agreement, among other things, to expand the space occupied by the Company at the property at which the Company’s corporate headquarters are located, and to extend the term of each lease agreement through June 2021, with an option to extend each lease for an additional term through June 2024.
Total lease expense | $				$ 0.6	$ 0.3	$ 0.3

Commitment and Contingencies -

Commitment and Contingencies - Summary of Annual Future Minimum Lease Payments (Detail) $ in Thousands	Dec. 31, 2016USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,017	$ 430
2,018	395
2,019	388
2,020	389
2,021	197
Total minimum payment required	$ 1,799

Employee Benefit Plan - Additio

Employee Benefit Plan - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution expense	$ 500,000	$ 0	$ 0
Non-elective employer contribution expense	$ 0	0	0
401(k) Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Description of defined contribution plan	The Company maintains a tax-qualified 401(k) retirement plan (“401(k) Plan”) for its U.S. employees. Eligible employees may make pre-tax 401(k) contributions under the 401(k) Plan, up to Internal Revenue Code limits. In addition, the Company, in its sole discretion, may make annual matching contributions and/or non-elective employer contributions to the 401(k) Plan. No such discretionary non-elective employer contributions were made during the years ended December 31, 2016, 2015 and 2014 and no such discretionary matching contributions were made during the years ended December 31, 2015 and 2014. During 2016, the Company has accrued for matching contributions that the Company may, in its discretion, make to the 401(k) Plan for the 2016 plan year (ending December 31, 2016) with accruals generally based on a matching contribution for each eligible employee that would be the lesser of: (1) 50% of the eligible employee's 2016 pre-tax 401(k) contributions and (2) 50% of up to 6% the eligible employee's 2016 eligible compensation.
Defined contribution benefit plan, non-elective employer contribution	$ 0	0	0
Defined contribution benefit plan, employer contribution		0	0
Employer contribution percentage on employees pre-tax contribution	50.00%
Employers contribution on employee's 6% compensation	50.00%
Employer matching contribution as percentage of eligible employee's compensation	6.00%
Foreign Retirement Plans [Member] | Entellus Medical Europe, Ltd. [Member]
Defined Contribution Plan Disclosure [Line Items]
Total contributions to retirement plans			$ 0
Foreign Retirement Plans [Member] | Maximum [Member] | Entellus Medical Europe, Ltd. [Member]
Defined Contribution Plan Disclosure [Line Items]
Total contributions to retirement plans	$ 100,000	$ 100,000

Segment and Geographical Data -

Segment and Geographical Data - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016Segment
Segment Reporting [Abstract]
Number of reportable segments	1

Segment and Geographical Data69

Segment and Geographical Data - Schedule of Total Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenue	$ 21,672	$ 17,880	$ 18,730	$ 16,902	$ 18,073	$ 14,804	$ 15,191	$ 13,502	$ 75,184	$ 61,570	$ 48,820
United States
Segment Reporting Information [Line Items]
Total revenue									71,648	60,911	$ 48,820
International
Segment Reporting Information [Line Items]
Total revenue									$ 3,536	$ 659

Subsequent Event - Additional I

Subsequent Event - Additional Information (Detail) - Scenario Forecast [Member] $ / shares in Units, shares in Millions	3 Months Ended
	Mar. 31, 2017USD ($)$ / sharesshares
Secondary Public Offering [Member]
Subsequent Event [Line Items]
Common stock, shares issued	2.9
Common stock offering price per share | $ / shares	$ 17
Proceeds from issuance of common stock, net of issuance costs | $	$ 45,400,000
Additional Share Purchase by Underwriters [Member]
Subsequent Event [Line Items]
Common stock, shares issued	0.5
Sale by Certain Existing Shareholders [Member]
Subsequent Event [Line Items]
Common stock sold by certain existing stockholders	1.2
Proceeds from sale of shares by existing selling stockholders | $	$ 0

Quarterly Results of Operatio71

Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 21,672	$ 17,880	$ 18,730	$ 16,902	$ 18,073	$ 14,804	$ 15,191	$ 13,502	$ 75,184	$ 61,570	$ 48,820
Cost of goods sold	5,613	4,648	4,459	4,000	4,330	3,431	3,348	2,949	18,720	14,058	10,754
Gross profit	16,059	13,232	14,271	12,902	13,743	11,373	11,843	10,553	56,464	47,512	38,066
Operating expenses
Selling and marketing	14,970	15,364	13,086	13,407	12,937	12,308	9,815	9,887	56,827	44,947	32,763
Research and development	1,960	2,047	1,873	1,912	1,387	1,392	1,308	1,300	7,792	5,387	4,307
General and administrative	5,966	4,807	3,838	3,949	3,914	3,230	3,074	2,816	18,560	13,034	6,097
Total operating expenses	22,896	22,218	18,797	19,268	18,238	16,930	14,197	14,003	83,179	63,368	43,167
Loss from operations	(6,837)	(8,986)	(4,526)	(6,366)	(4,495)	(5,557)	(2,354)	(3,450)	(26,715)	(15,856)	(5,101)
Other income (expense)
Interest income	50	75	83	70	53	47	50	21	278	171	75
Interest expense	(562)	(562)	(562)	(562)	(562)	(561)	(562)	(919)	(2,248)	(2,604)	(1,904)
Other non-operating (expense) income	3	(12)	(16)	(14)	(9)		(2)		(39)	(11)	1
Total other expense, net					(518)	(514)	(514)	(898)
Loss before income tax expense	(7,346)	(9,485)	(5,021)	(6,872)					(28,724)	(18,300)	(6,929)
Income tax (expense) benefit	28	(34)							(6)
Net loss	$ (7,318)	$ (9,519)	$ (5,021)	$ (6,872)	$ (5,013)	$ (6,071)	$ (2,868)	$ (4,348)	$ (28,730)	$ (18,300)	$ (6,929)
Net loss per share, basic and diluted	$ (0.39)	$ (0.50)	$ (0.27)	$ (0.37)	$ (0.27)	$ (0.32)	$ (0.15)	$ (0.35)	$ (1.53)	$ (1.06)	$ (4.62)
Weighted average common shares used to compute net loss per share, basic and diluted	18,876	18,855	18,824	18,801	18,784	18,738	18,718	12,542	18,839	17,217	1,499

Schedule II - Valuation and Q72

Schedule II - Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 135	$ 150	$ 135
Additions	34	46	49
Deductions	19	61	34
Ending Balance	150	135	150
Reserve for Sales Returns and Allowances [Member]
Valuation And Qualifying Accounts Disclosure [Line Items]
Beginning Balance	251	140	100
Additions	66	230	120
Deductions	159	119	80
Ending Balance	$ 158	$ 251	$ 140