Conformis (CFMS) 10-K 9 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 28, 2018	Jun. 30, 2017
Document and Entity Information
Entity Registrant Name	CONFORMIS INC
Entity Central Index Key	1,305,773
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		60,861,852
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Entity Public Float			$ 94,870,205

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 18,348	$ 37,257
Investments	26,880	28,242
Accounts receivable, net	13,200	14,675
Inventories	9,184	11,720
Prepaid expenses and other current assets	2,246	3,954
Total current assets	69,858	95,848
Property and equipment, net	16,514	15,084
Other Assets
Restricted cash	462	300
Intangible assets, net	210	746
Goodwill	6,731	753
Other long-term assets	23	79
Total assets	93,798	112,810
Current liabilities
Accounts payable	4,891	5,474
Accrued expenses	7,720	8,492
Deferred revenue	305	305
Total current liabilities	12,916	14,271
Other long-term liabilities	651	164
Deferred tax liabilities	37	0
Deferred revenue	4,014	4,320
Long-term debt, less debt issuance costs	29,667	0
Total liabilities	47,285	18,755
Commitments and contingencies	0	0
Stockholders’ equity
Preferred stock, $0.00001 par value:	0	0
Common stock, $0.00001 par value:	0	0
Additional paid-in capital	486,570	476,486
Accumulated deficit	(436,821)	(382,930)
Accumulated other comprehensive (loss) income	(3,236)	499
Total stockholders’ equity	46,513	94,055
Total liabilities and stockholders’ equity	$ 93,798	$ 112,810

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	45,528,519	43,399,547
Common stock, shares outstanding	45,528,519	43,399,547

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Product	$ 77,100	$ 78,921	$ 62,791
Royalty	1,015	978	4,096
Total revenue	78,115	79,899	66,887
Cost of revenue	49,301	53,192	45,102
Gross profit	28,814	26,707	21,785
Operating expenses
Sales and marketing	38,788	41,086	37,558
Research and development	17,136	16,608	16,997
General and administrative	28,737	25,157	23,191
Total operating expenses	84,661	82,851	77,746
Loss from operations	(55,847)	(56,144)	(55,961)
Other income and expenses
Interest income	491	487	138
Interest expense	(2,119)	(138)	(1,385)
Loss on extinguishment of debt	0	0	(205)
Foreign currency transaction income (loss)	4,057	(1,607)	0
Other income (expense)	0	(123)	208
Total other income (expenses), net	2,429	(1,381)	(1,244)
Loss before income taxes	(53,418)	(57,525)	(57,205)
Income tax provision	162	63	41
Net loss	$ (53,580)	$ (57,588)	$ (57,246)
Net loss per share - basic and diluted	$ (1.24)	$ (1.39)	$ (2.60)
Weighted average common shares outstanding - basic and diluted	43,343,459	41,521,629	21,993,066

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (53,580)	$ (57,588)	$ (57,246)
Other comprehensive income (loss)
Foreign currency translation adjustments	(3,709)	1,027	(24)
Change in unrealized gain (loss) on available-for-sale securities, net of tax	(26)	(7)	0
Comprehensive loss	$ (57,315)	$ (56,568)	$ (57,270)

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholder's Equity - USD ($) $ in Thousands	Total	Common Stock	Series D convertible preferred stock	Series E-1 convertible preferred stock	Series E-2 convertible preferred stock	Preferred StockConvertible Preferred Stock	Preferred StockSeries D convertible preferred stock	Preferred StockSeries E-1 convertible preferred stock	Preferred StockSeries E-2 convertible preferred stock	Common Stock	Additional Paid-in Capital	Additional Paid-in CapitalCommon Stock	Additional Paid-in CapitalSeries D convertible preferred stock	Additional Paid-in CapitalSeries E-1 convertible preferred stock	Additional Paid-in CapitalSeries E-2 convertible preferred stock	Retained Earnings	Accumulated other comprehensive income (loss)	Restricted stock awardsCommon Stock
Beginning balance at Dec. 31, 2014	$ 49,827					$ 0				$ 0	$ 318,420					$ (268,096)	$ (497)
Preferred stock, shares outstanding, beginning balance (in shares) at Dec. 31, 2014						50,985,652
Common stock, shares outstanding, beginning balance (in shares) at Dec. 31, 2014										4,286,164
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, exercised options (in shares)										383,458
Adjustments to additional paid in capital, share-based compensation, stock options	806										806
Stock issued during period, shares, new issues (in shares)										10,350,000								174,530
Stock issued during period, value, new issues	139,766										139,766
Warrants issued	0
Stock issued during period, shares, warrants exercised							321,854	300,059	200,996	11,734
Stock issued during period, value, warrants exercised		$ 18	$ 450	$ 2,400	$ 1,608							$ 18	$ 450	$ 2,400	$ 1,608
Issuance of common stock - preferred stock conversion to common stock						(51,808,561)				(25,904,241)
Stock-based compensation expense	3,607										3,607
Net loss	(57,246)															(57,246)
Foreign currency translation adjustments	(24)
Ending balance at Dec. 31, 2015	141,212					$ 0				$ 0	467,075					(325,342)	(521)
Preferred stock, shares outstanding, ending balance (in shares) at Dec. 31, 2015						0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in period	$ (24)																(24)
Common stock, shares outstanding, ending balance (in shares) at Dec. 31, 2015	41,110,127									41,110,127
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, exercised options (in shares)										1,467,692
Adjustments to additional paid in capital, share-based compensation, stock options	$ 4,087										4,087
Stock issued during period, shares, new issues (in shares)																		804,019
Warrants issued	0
Stock issued during period, shares, warrants exercised										17,709
Stock-based compensation expense	5,324										5,324
Net loss	(57,588)															(57,588)
Foreign currency translation adjustments	1,027
Ending balance at Dec. 31, 2016	$ 94,055					$ 0				$ 0	476,486					(382,930)	499
Preferred stock, shares outstanding, ending balance (in shares) at Dec. 31, 2016	0					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in period	$ 1,020																1,020
Common stock, shares outstanding, ending balance (in shares) at Dec. 31, 2016	43,399,547									43,399,547
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative-effect adjustment from adoption of ASU 2016-09	$ 0										311					(311)
Issuance of common stock, exercised options (in shares)										535,734
Adjustments to additional paid in capital, share-based compensation, stock options	$ 2,108										2,108
Stock issued during period, shares, new issues (in shares)	228,946									228,946								1,195,196
Stock issued during period, value, new issues	$ 1,023										1,023
Stock issued during period, acquisitions (in shares)	169,096									169,096
Stock issued during period, acquisitions	$ 594										594
Warrants issued	$ 594
Issuance of common stock - preferred stock conversion to common stock	(25,904,241)
Stock-based compensation expense	$ 6,048										6,048
Net loss	(53,580)															(53,580)
Foreign currency translation adjustments	(3,709)
Ending balance at Dec. 31, 2017	$ 46,513					$ 0				$ 0	$ 486,570					$ (436,821)	(3,236)
Preferred stock, shares outstanding, ending balance (in shares) at Dec. 31, 2017	0					0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Change in period	$ (3,735)																$ (3,735)
Common stock, shares outstanding, ending balance (in shares) at Dec. 31, 2017	45,528,519									45,528,519

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net loss	$ (53,580)	$ (57,588)	$ (57,246)
Adjustments to reconcile net loss to net cash used by operating activities:
Depreciation and amortization expense	3,669	3,153	2,619
Amortization of debt discount	0	7	135
Stock-based compensation expense	6,048	5,324	3,607
Provision for bad debts on trade receivables	(15)	188	359
Impairment of long term assets	1,113	123	0
Disposal of long term assets	0	16	2
Loss on extinguishment of debt	0	0	205
Non-cash interest expense	100	0	0
Amortization/accretion on investments	202	315	0
Deferred tax	37	0	0
Changes in operating assets and liabilities:
Accounts receivable	1,490	4	(6,107)
Inventories	2,535	(200)	(3,829)
Prepaid expenses and other assets	1,770	(1,550)	(1,045)
Accounts payable and accrued liabilities	(1,406)	1,437	1,969
Deferred royalty revenue	(306)	(305)	4,932
Other long-term liabilities	487	(56)	(51)
Net cash used in operating activities	(37,856)	(49,132)	(54,450)
Cash flows from investing activities:
Acquisition of property and equipment	(5,233)	(7,161)	(4,643)
Business acquisition, net of cash acquired	(5,780)	0	0
(Increase) decrease in restricted cash	(162)	300	3,837
Purchase of investments	(30,991)	(65,614)	0
Maturity of investments	32,125	37,050	0
Net cash used in investing activities	(10,041)	(35,425)	(806)
Cash flows from financing activities:
Proceeds from exercise of common stock options	2,108	4,087	806
Proceeds from exercise of common stock warrant	0	0	18
Proceeds from exercise of preferred stock warrant	0	0	4,458
Debt issuance costs	(434)	0	0
Proceeds from issuance of debt	30,000	0	0
Payments on long-term debt	0	(485)	(10,278)
Payment on extinguishment of debt	0	0	(205)
Net proceeds from issuance of common stock	1,023	0	139,766
Net cash provided by financing activities	32,697	3,602	134,565
Foreign exchange effect on cash and cash equivalents	(3,709)	1,027	(24)
(Decrease) increase in cash and cash equivalents	(18,909)	(79,928)	79,285
Cash and cash equivalents, beginning of period	37,257	117,185	37,900
Cash and cash equivalents, end of period	18,348	37,257	117,185
Supplemental information:
Cash paid for income taxes	36	52	187
Cash paid for interest	1,449	48	1,284
Noncash investing and financing activities
Issuance of common stock for business acquisition	$ 594	$ 0	$ 0

Organization and Basis of Prese

Organization and Basis of Presentation	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization and Basis of Presentation	Organization and Basis of Presentation ConforMIS, Inc. and its subsidiaries (the “Company”) is a medical technology company that uses its proprietary iFit Image-to-Implant technology platform to develop, manufacture and sell joint replacement implants that are individually sized and shaped, which the Company refers to as customized, to fit each patient’s unique anatomy. The Company’s proprietary iFit® technology platform is potentially applicable to all major joints. The Company offers a broad line of customized knee implants designed to restore the natural shape of a patient’s knee. The Company was incorporated in Delaware and commenced operations in 2004. The Company introduced its iUni and iDuo in 2007, its iTotal CR in 2011 and its iTotal PS in 2015. The Company has its corporate offices in Billerica, Massachusetts. These consolidated financial statements and related notes have been prepared assuming that the Company will continue as a going concern, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. Liquidity and operations Since the Company’s inception in June 2004, it has financed its operations primarily through private placements of preferred stock, its initial public offering in July 2015, bank debt and convertible debt financings, equipment purchase loans, and product revenue beginning in 2007. The Company has not yet attained profitability and continues to incur operating losses and negative operating cash flows, which adversely impacts the Company's ability to continue as a going concern. At December 31, 2017 , the Company had an accumulated deficit of $436.8 million . At December 31, 2017 , the Company had cash and cash equivalents and investments of $45.2 million and $0.5 million in restricted cash allocated to a lease deposit. On January 6, 2017, the Company entered into the 2017 Secured Loan Agreement with Oxford consisting of three term loans issued by Oxford with $15 million issued for each of the first two term loans and $20 million issued for the third term loan, in each case, subject to the satisfaction of certain revenue milestones and customary drawdown conditions. Through the term loan facility with Oxford, the Company accessed the initial $15 million of borrowings at closing and another $15 million of borrowings on June 30, 2017, with an additional $20 million available, at its option, through June 2018, subject to the satisfaction of certain revenue milestones and customary drawdown conditions, which the Company does not expect will be satisfied by the end of June 2018. For further information regarding this facility, see "Note K-Debt and Notes Payable-2017 Secured Loan Agreement" to the consolidated financial statements appearing in this Annual Report on Form 10-K. In January 2017, the Company filed a shelf registration statement on Form S-3, which was declared effective by the SEC on May 9, 2017 (the "Shelf Registration Statement"). The Shelf Registration Statement allows the Company to sell from time to time up to $200 million of common stock, preferred stock, debt securities, warrants, or units comprised of any combination of these securities, for its own account in one or more offerings. On May 10, 2017, the Company filed with the SEC a prospectus supplement (the “Prospectus Supplement”) for the sale and issuance of up to $50 million of its common stock and entered into a Distribution Agreement with Canaccord Genuity, Inc. ("Canaccord"), pursuant to which Canaccord agreed to sell shares of the Company's common stock from time to time, as our agent, in an “at-the-market” offering ("ATM") as defined in Rule 415 promulgated under the U.S. Securities Act of 1933, as amended. The Company is not obligated to sell any shares under the Distribution Agreement. As of December 31, 2017 , the Company has sold 228,946 Shares under the Distribution Agreement resulting in net proceeds of $1.0 million . On January 29, 2018, the Company closed an offering of its common stock off of the Shelf Registration Statement and issued and sold 15,333,333 shares of its common stock (including 2,000,000 shares of common stock issued in connection with the exercise in full by the underwriters of their over-allotment option) at a public offering price of $1.50 per share, for aggregate net proceeds of approximately $21.3 million . For further information regarding this public offering, see "Note R - Subsequent Events - 2018 Common Stock Offering" in the financial statements and related notes appearing elsewhere in this Annual Report on Form 10-K. The Company anticipates that its principal sources of funds in the future will be revenue generated from the sales of its products, potential future capital raises through the issuance of equity or other securities, revenue that may be generated in connection with licensing its intellectual property, and potentially borrowings under our 2017 Secured Loan Agreement. The Company expects that its existing cash and cash equivalents as of December 31, 2017 , including borrowings made under its 2017 Secured Loan Agreement, coupled with the $21.3 million of net proceeds from the 2018 Common Stock Offering, and anticipated revenue from operations will enable the Company to fund its operating expenses and capital expenditure requirements and pay its debt service as it becomes due for at least the next 12 months from the date of filing. Management has based this expectation on assumptions that may prove to be wrong, such as the revenue that it expects to generate from the sale of its products and the gross profit the Company expects to generate from that revenue, and it could use its capital resources sooner than we expect. In the event the Company’s resources are not sufficient to fund its operations, the Company may need to engage in equity or debt financings to secure additional funds. The Company may not be able to obtain additional financing on terms favorable to the Company, or at all. Basis of presentation and use of estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenue and expenses during the reporting periods. The most significant estimates used in these consolidated financial statements include revenue recognition, accounts receivable valuation, inventory reserves, goodwill valuation, intangible valuation, purchase accounting, impairment assessments, equity instruments, stock compensation, income tax reserves and related allowances, and the lives of property and equipment. Actual results may differ from those estimates.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Concentrations of credit risk and other risks and uncertainties Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents and accounts receivable. The Company maintains the majority of its cash with accredited financial institutions. The Company and its contract manufacturers rely on sole source suppliers and service providers for certain components. There can be no assurance that a shortage or stoppage of shipments of the materials or components that the Company purchases will not result in a delay in production or adversely affect the Company’s business. On an on-going basis, the Company validates alternate suppliers relative to certain key components as needed. For the years ended December 31, 2017 , 2016 and 2015 , no customer represented greater than 10% of revenue. There were no customers that represented greater than 10% of total gross receivable balance at December 31, 2017 and 2016 . Principles of consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries including ImaTx, Inc. ("ImaTx"), ConforMIS Europe GmbH, ConforMIS UK Limited and ConforMIS Hong Kong Limited. All material intercompany balances and transactions have been eliminated in consolidation. Cash and cash equivalents The Company considers all highly liquid investment instruments with original maturities of 90 days or less when purchased, to be cash equivalents. The Company’s cash equivalents consist of demand deposits, money market accounts and repurchase agreements on deposit with certain financial institutions, in addition to cash deposits in excess of federally insured limits. Demand deposits are carried at cost which approximates their fair value. Money market accounts are carried at fair value based upon level 1 inputs. Repurchase agreements are valued using level 2 inputs. See “Note C — Fair Value Measurements” below. The associated risk of concentration is mitigated by banking with credit worthy financial institutions. The Company had $2.2 million as of December 31, 2017 and $1.6 million as of December 31, 2016 held in foreign bank accounts, that was not federally insured. In addition, the Company has recorded restricted cash of $0.5 million as of December 31, 2017 and $0.3 million as of December 31, 2016 , respectively. Restricted cash consisted of security provided for lease obligations. Investment securities The Company classifies its investment securities as available-for-sale. Those investments with maturities less than 12 months at the date of purchase are considered short-term investments. Those investments with maturities greater than 12 months at the date of purchase are considered long-term investments. The Company’s investment securities classified as available-for-sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security using the constant yield method. Dividend and interest income are recognized when earned and reported in other income. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold. Fair value of financial instruments Certain of the Company’s financial instruments, including cash and cash equivalents (excluding money market funds), accounts receivable, accounts payable, accrued expenses and other liabilities are carried at cost, which approximates their fair value because of the short-term maturity. Based on borrowing rates currently available to the Company for loans with similar terms, the carrying value of the Company’s long-term debt approximates its fair value. Accounts receivable and allowance for doubtful accounts Accounts receivable consist of billed and unbilled amounts due from medical facilities. Upon completion of a procedure, revenue is recognized and an unbilled receivable is recorded. Upon receipt of a purchase order number from a medical facility a billed receivable is recorded and the unbilled receivable is reversed. As a result, the unbilled receivable balance fluctuates based on the timing of the Company's receipt of purchase order numbers from the medical facilities. In estimating whether accounts receivable can be collected, the Company performs evaluations of customers and continuously monitors collections and payments and estimates an allowance for doubtful accounts based on the aging of the underlying invoices, collections experience to date and any specific collection issues that have been identified. The allowance for doubtful accounts is recorded in the period in which revenue is recorded or when collection risk is identified. Inventories Inventories consist of raw materials, work-in-process components and finished goods. Inventories are stated at the lower of cost, determined using the first-in first-out method, or net realizable value. The Company regularly reviews its inventory quantities on hand and related cost and records a provision for any excess or obsolete inventory based on its estimated forecast of product demand and existing product configurations. The Company also reviews its inventory value to determine if it reflects the lower of cost or market based on net realizable value. Appropriate consideration is given to inventory items sold at negative gross margin, purchase commitments and other factors in evaluating net realizable value. During the years ended December 31, 2017 , 2016 and 2015 , the Company recognized provisions of $2.6 million , $3.5 million and $2.7 million , respectively, to adjust its inventory value to the lower of cost or market for estimated unused product related to known and potential cancelled cases, which is included in cost of revenue. Property and equipment Property and equipment is stated at cost less accumulated depreciation and is depreciated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized over their useful life or the life of the lease, whichever is shorter. Assets capitalized under capital leases are amortized in accordance with the respective class of assets and the amortization is included with depreciation expense. Maintenance and repair costs are expensed as incurred. Business combinations and purchase accounting The Company includes the results of operations of the businesses that it acquires as of the applicable acquisition date. The purchase price of the acquisition is allocated to the assets acquired and liabilities assumed based on their estimated fair values. The excess of the purchase price over the fair values of these identifiable assets and liabilities is recorded as goodwill. Acquisition-related expenses are recognized separately from the business combination and are expensed as incurred. Intangibles and other long-lived assets Intangible assets consist of developed technology acquired as part of the ImaTx spin-out transaction in 2004 and a favorable lease asset from the Broad Peak Manufacturing, LLC ("BPM") acquisition in August 2017. Intangible assets are carried at cost less accumulated amortization. The Company tests impairment of long-lived assets when events or changes in circumstances indicate that the assets might be impaired. For assets with determinable useful lives, amortization is computed using the straight-line method over the estimated economic lives of the respective intangible assets. Furthermore, periodically the Company assesses whether long-lived assets, including intangible assets, should be tested for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. The amount of impairment, if any, is measured based on fair value, which is determined using estimated undiscounted cash flows to be generated from such assets or group of assets. If the cash flow estimates or the significant operating assumptions upon which they are based change in the future, the Company may be required to record impairment charges. In 2017, the Company recognized $1.1 million in impairment charges in general and administrative expense of which $0.8 million related to the discontinuance of a software capital project and $0.3 million related to intellectual property rights licensed as part of the ImaTx spin-out transaction in 2004. In 2016, a $0.1 million impairment charge was recognized in connection with certain manufacturing equipment previously purchased that will be returned to the seller in exchange for credit toward a future purchase, which value is less than the book value of the equipment. Goodwill Goodwill relates to amounts that arose in connection with the acquisition of ImaTx, Inc. in 2009 and the acquisition of BPM in August 2017. The Company tests goodwill at least annually for impairment, or more frequently when events or changes in circumstances indicate that the assets may be impaired. This impairment test is performed annually during the fourth quarter at the reporting unit level. Goodwill may be considered impaired if the carrying value of the reporting unit, including goodwill, exceeds the reporting unit’s fair value. The Company is comprised of one reporting unit. When testing goodwill for impairment, the Company first assesses the qualitative factors to determine whether it is more likely than not that the fair value of its reporting unit is less than its carrying amount. This qualitative analysis is used as a basis for determining whether it is necessary to perform the one-step goodwill impairment analysis. If the Company determines that it is more likely than not that its fair value is less than its carrying amount, then the one-step goodwill impairment test will be performed. If the one-step approach is performed, the Company will estimate fair value of the reporting unit using the market approach to compare the Company's market capitalization with the carrying amount of its net assets on the date of the test, since the Company has only one reporting unit. An impairment of goodwill is recognized when the carrying amount exceeds the fair value. During the Company's 2017 impairment test, the Company's qualitative analysis indicated that a step one analysis is required to determine the fair value of the reporting unit. The Company used the market approach noting the reporting unit's fair value was substantially in excess of its carrying value. During the years ended December 31, 2016 and 2015 , there were no triggering events which would require goodwill impairment assessment. Revenue recognition Product The Company generates revenue from the sale of customized implants and instruments to medical facilities through the use of a combination of direct sales personnel, independent sales representatives and distributors in the United States, Germany, the United Kingdom, Austria, Ireland, Switzerland, Singapore, Hong Kong, Malaysia and Monaco . Revenue was recognized when all of the following criteria are met: • persuasive evidence of an arrangement exists; • the sales price is fixed or determinable; • collection of the relevant receivable is probable at the time of sale; and • delivery has occurred or services have been rendered. The Company recognizes revenue upon completion of the procedure, which represents satisfaction of the required revenue recognition criteria. Once the revenue recognition criteria have been satisfied the Company does not offer rights of return or price protection and there are no post-delivery obligations. Royalty The Company accounted for its agreements with Wright Medical and MicroPort under ASC 605-25, Multiple-Element Arrangements and Staff Accounting Bulletin No. 104, Revenue Recognition (ASC 605). In accordance with ASC 605, the Company was required to identify and account for each of the separate units of accounting. The Company identified the relative selling price for each and then allocated the total consideration based on their relative values. Additionally, the Company recognized an initial $5.1 million in aggregate as deferred royalty revenue, to be recognized as royalty revenue ratably through 2031. The on-going royalty from MicroPort was recognized as royalty revenue upon receipt of payment. Shipping and handling costs Amounts invoiced to customers for shipping and handling are classified as revenue. Shipping and handling costs incurred are included in general and administrative expense. Shipping and handling expense was $1.4 million , $1.6 million and $2.7 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Taxes collected from customers and remitted to government authorities The Company’s policy is to present taxes collected from customers and remitted to government authorities on a net basis and not to include tax amounts in revenue. Research and development expense The Company’s research and development costs consist of engineering, product development, quality assurance, clinical and regulatory expense. These costs primarily relate to employee compensation, including salary, benefits and stock-based compensation. The Company also incurs costs related to consulting fees, materials and supplies, and marketing studies, including data management and associated travel expense. Research and development costs are expensed as incurred. Advertising expense Advertising costs are expensed as incurred, which are included in sales and marketing. Advertising expense was $0.4 million for the year ended December 31, 2017 , $0.3 million for the year ended December 31, 2016 and $0.3 million for the year ended December 31, 2015 . Segment reporting Operating segments are defined as components of an enterprise about which separate financial information is available and is evaluated on a regular basis by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources to an individual segment and in assessing performance of the segment. The Company’s chief operating decision-maker is its chief executive officer. The Company’s chief executive officer reviews financial information presented on an aggregate basis for purposes of allocating resources and evaluating financial performance. The Company has one business segment and there are no segment managers who are held accountable for operations, operating results and plans for products or components below the aggregate Company level. Accordingly, in light of the Company’s current product offerings, management has determined that the primary form of internal reporting is aligned with the offering of the ConforMIS customized joint replacement products and that the Company operates as one segment. See “Note O-Segment and Geographic Data”. Comprehensive loss At December 31, 2017 and 2016 , accumulated other comprehensive loss consists of foreign currency translation adjustments and changes in unrealized gain and loss of available-for-sale securities, net of tax. The following table summarizes accumulated beginning and ending balances for each item in Accumulated other comprehensive income (loss) (in thousands): Foreign currency translation adjustments Change in unrealized gain (loss) on available-for-sale securities, net of tax Accumulated other comprehensive income (loss) Balance December 31, 2016 $ 506 $ (7 ) $ 499 Change in period (3,709 ) (26 ) (3,735 ) Balance December 31, 2017 $ (3,203 ) $ (33 ) $ (3,236 ) Foreign currency translation and transactions The assets and liabilities of the Company’s foreign operations are translated into U.S. dollars at current exchange rates at the balance sheet date, and income and expense items are translated at average rates of exchange prevailing during the year. Net translation gains and losses are recorded in Accumulated other comprehensive (loss) income. Gains and losses realized from transactions denominated in foreign currencies, including intercompany balances not of a long-term investment nature, are included in the consolidated statements of operations. 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 consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases, operating losses and tax credit carry forwards. 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 effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. In evaluating the need for a valuation allowance, the Company considers all reasonably available positive and negative evidence, including recent earnings, expectations of future taxable income and the character of that income. In estimating future taxable income, the Company relies upon assumptions and estimates of future activity including the reversal of temporary differences. Presently, the Company believes that a full valuation allowance is required to reduce deferred tax assets to the amount expected to be realized. The tax benefit from an uncertain tax position is only recognized if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the consolidated financial statements from these positions are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate resolution. The Company reviews its tax positions on an annual basis and more frequently as facts surrounding tax positions change. Based on these future events, the Company may recognize uncertain tax positions or reverse current uncertain tax positions, the impact of which would affect the consolidated financial statements. The Company has operations in Germany and, until July 1,2017, the United Kingdom. The operating results of these operations will be permanently reinvested in those jurisdictions. As a result, the Company has only provided for income taxes at local rates when required. Accounting Standard Update ("ASU") No. 2016-09, "Compensation - Stock Compensation", was issued and adopted in January 2017. ASU 2016-09 eliminates additional paid in capital ("APIC") pools and requires excess tax benefits and tax deficiencies to be recorded in the income statement when the awards vest or are settled. In addition, modified retrospective adoption of ASU 2016-09 eliminates the requirement that excess tax benefits be realized (i.e., through a reduction in income taxes payable) before the Company can recognize them and therefore, it has accounted for a cumulative-effect adjustment of $7.7 million during the year ended December 31, 2017 to record excess tax benefits. Since the Company has a full valuation allowance on all deferred taxes, this has no impact on retained earnings or the tax position of the Company. On December 22, 2017, the Tax Act was enacted to provide for reconciliation pursuant to titles II and V of the concurrent resolution on the budget for fiscal year 2018. The tax act reduces the U.S. federal corporate income tax rate effective January 1, 2018 from its current 35% rate to a new 21% corporate rate and impose a one-time transition tax on unremitted foreign earnings on foreign subsidiaries. The Company has not yet completed its evaluation of the impact of the changes in the tax bill but expects the net impact of these changes will be favorable to its financial results in future fiscal quarters. Medical device excise tax The Company has been subject to the Health Care and Education Reconciliation Act of 2010 (the “Act”), which imposes a tax equal to 2.3% on the sales price of any taxable medical device by a medical device manufacturer, producer or importer of such device. Under the Act, a taxable medical device is any device defined in Section 201(h) of the Federal Food, Drug, and Cosmetic Act, intended for humans, which includes an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including any component, part, or accessory, which meets certain requirements. The Consolidated Appropriations Act of 2016 includes a two-year moratorium on the medical device excise tax, which moratorium suspended taxes on the sale of a taxable medical device by the manufacturer, producer, or importer of the device during the period beginning on January 1, 2016 and ending on December 31, 2017. As such, the Company did not incur medical device excise tax expense for the years ended December 31, 2017 and 2016 . The Company incurred medical device excise tax expense of $0.8 million for the year ended December 31, 2015 . On January 22, 2018, legislation was passed that suspends the medical device excise tax for sales in 2018 and 2019. The tax is not scheduled to take effect again until sales on or after January 1, 2020. It is unclear at this time if the suspension will be further extended, and we are currently subject to the tax after December 31, 2019. Stock-based compensation The Company accounts for stock-based compensation in accordance with ASC 718, Stock Based Compensation. ASC 718 requires all stock-based payments to employees and consultants, including grants of stock options, to be recognized in the consolidated statements of operations based on their fair values. The Company uses the Black-Scholes option pricing model to determine the weighted-average fair value of options granted and recognizes the compensation expense of stock-based awards on a straight-line basis over the vesting period of the award. The determination of the fair value of stock-based payment awards utilizing the Black-Scholes option pricing model is affected by the stock price, exercise price, and a number of assumptions, including expected volatility of the stock, expected life of the option, risk-free interest rate and expected dividends on the stock. The Company evaluates the assumptions used to value the awards at each grant date and if factors change and different assumptions are utilized, stock-based compensation expense may differ significantly from what has been recorded in the past. 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. Prior to the Company’s IPO in July 2015, the exercise price of stock option awards was determined by the Company's board of directors based on a number of factors in determining the option price, including: (1) past sales of the Company’s convertible preferred stock, and the rights, preferences and privileges of the Company stock, (2) obtaining FDA 510(k) clearance, and (3) achievement of budgeted results. See “Note M——Stockholders’ Equity” for a summary of the stock option activity under the Company’s stock-based compensation plan. Net loss per share The Company calculates net loss per share in accordance with ASC 260, "Earnings per Share". Basic earnings per share (“EPS”) is calculated by dividing the net income or loss for the period by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted EPS is computed by dividing the net income or loss for the period by the weighted average number of common shares outstanding for the period and the weighted average number of dilutive common stock equivalents outstanding for the period determined using the treasury stock method. The following table sets forth the computation of basic and diluted earnings per share attributable to stockholders (in thousands, except share and per share data): Years Ended December 31, (in thousands, except share and per share data) 2017 2016 2015 Numerator: Numerator for basic and diluted loss per share: Net loss $ (53,580 ) $ (57,588 ) $ (57,246 ) Denominator: Denominator for basic loss per share: Weighted average shares 43,343,459 41,521,629 21,993,066 Basic loss per share attributable to ConforMIS, Inc. stockholders $ (1.24 ) $ (1.39 ) $ (2.60 ) Diluted loss per share attributable to ConforMIS, Inc. stockholders $ (1.24 ) $ (1.39 ) $ (2.60 ) The following table sets forth potential shares of common stock equivalents that are not included in the calculation of diluted net loss per share because to do so would be anti-dilutive as of the end of each period presented: Years Ended December 31, 2017 2016 2015 Series A Preferred — — 873,591 Series B Preferred — — 1,144,885 Series C Preferred — — 1,256,752 Series D Preferred — — 3,410,570 Series E-1 Preferred — — 3,748,578 Series E-2 Preferred — — 2,628,037 Common stock warrants — 34,709 303,931 Stock options 365,105 1,959,030 3,566,421 Total 365,105 1,993,739 16,932,765 Recent accounting pronouncements In May 2017, the FASB issued ASU No. 2017-09, "Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting". This ASU provides clarification on when changes to the terms or conditions of a share-based payment award must be accounted for as a modification. The guidance will be effective in the first quarter of 2018, with early adoption permitted. The Company is does not believe that the adoption of ASU 2017-09 will have a material impact on its consolidated financial statements and expects to adopt this pronouncement commencing in the first quarter of 2018. In January 2017, the FASB issued ASU No. 2017-04, "Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment". This ASU removes the second step of the two-step test to determine goodwill impairment previously required. Entities will now apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. The guidance will be effective in the first quarter of 2020, with early adoption permitted. The Company has elected to early adopt this new pronouncement in 2017 noting no material impact on its consolidated financial statements . In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230) Restricted Cash a consensus of the FASB Emerging Issues Task Force”. The standard requires restricted cash and cash equivalents to be included with cash and cash equivalents on the statement of cash flows. The guidance will be effective in the first quarter of 2018, with early adoption permitted. The Company evaluated the impact of this pronouncement noting the Company's cash flow disclosure currently reflects ASU No. 2016-18 disclosure requirements. The Company expects to adopt this pronouncement commencing in the first quarter of 2018. In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)." This ASU amends various aspects of existing guidance for leases and requires additional disclosures about leasing arrangements. It will require companies to recognize lease assets and lease liabilities by lessees for those leases classified as operating leases under GAAP. Topic 842 retains a distinction between finance leases and operating leases. The classification criteria for distinguishing between finance leases and operating leases are substantially similar to the classification criteria for distinguishing between capital leases and operating leases in the previous leases guidance. This ASU is effective for annual periods beginning after December 15, 2018, including interim periods within those fiscal years; earlier adoption is permitted. In the financial statements in which the ASU is first applied, leases shall be measured and recognized at the beginning of the earliest comparative period presented with an adjustment to equity. Practical expedients are available for election as a package and if applied consistently to all leases. The Company is currently evaluating the impact of this pronouncement on its consolidated financial statements and expects to adopt this pronouncement commencing in the first quarter of 2019. In May 2014, the FASB issued ASU No. 2014-9, “Revenue from Contracts with Customers (Topic 606)”. ASU 2014-9 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying the revenue model to contracts within its scope, an entity identifies the contract(s) with a customer, identifies the performance obligations in the contract, determines the transaction price, allocates the transaction price to the performance obligations in the contract, and recognizes revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 applies to all contracts with customers that are within the scope of other topics in the FASB Accounting Standards Codification. ASU 2014-09 also requires significantly expanded disclosures about revenue recognition. Companies have the option of using either a full retrospective or a modified retrospective approach to adopt the guidance. In March 2016, the FASB issued ASU No 2016-08, "Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net)", which clarifies the implementation guidance on principal versus agent considerations. The guidance includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to the customers. In April 2016, the FASB issued ASU 2016-10, "Identifying Performance Obligations and Licensing" ("ASU 2016-10"). This ASU clarifies two aspects of ASU 2014-09, "Revenue from Contracts with Customers (Topic 606): identifying performance obligations and the licensing implementation guidance". Disclosure requirements are expanded regarding an entity’s assumptions, models and methods of estimations of the allowance. In November 2017, the FASB issued ASU 2017-14, "Income Statement - Reporting Comprehensive Income (Topic 220), Revenue Recognition (Topic 605), and Revenue from Contracts with Customers (Topic 606)", which amends the ASU 2016-10 to align SEC guidance with the new guidance in ASC 606. The Company has completed its assessment process to evaluate the impact, and will adopt this pronouncement and related disclosures commencing in the first quarter of 2018. The Company plans to adopt this standard using the modified retrospective approach as of January 1, 2018, which will apply to all contracts not completed as of January 1, 2018. The adoption of ASC 606 will require additional disclosure around the Company’s revenue recognition in its financial statements. The Company has established a cross-functional coordinated implementation team and engaged a third party consultant to assist with the assessment and implementation. The Company has completed the scoping and planning phase of the project, identified and reviewed customer contracts for each of its revenue streams, including royalty revenue, and has evaluated the results of those reviews relative to the new standard. Based on the results of the procedures, the Company does not expect a material impact on its consolidated financial statements with regards to revenue recognized from the sale of its product to customers. The Company expects that, based on its assessment, certain royalty revenue associated with the 2015 license agreements with Wright Medical and MicroPort will be accelerated upon the adoption of this new standard which will require an adjustment to retained earnings for approximately $4 million . The Company has also completed its evaluation of changes to its processes and int

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Fair Value Measurements topic of the FASB Codification establishes a framework for measuring fair value in accordance with US GAAP, clarifies the definition of fair value within that framework and expands disclosures about fair value measurements. This guidance requires disclosure regarding the manner in which fair value is determined for assets and liabilities and establishes a three-tiered value hierarchy into which these assets and liabilities must be grouped, based upon significant levels of inputs as follows: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Observable inputs, other than Level 1 prices, such as quoted prices in active markets for similar assets and liabilities, quoted prices for identical or similar assets and liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. This includes certain pricing models, discounted cash flow methodologies and similar techniques that use significant unobservable inputs. The Company's investment policy is consistent with the definition of available-for-sale securities. All investments have been classified within Level 1 or Level 2 of the fair value hierarchy because of the sufficient observable inputs for revaluation. The Company's Level 1 cash and equivalents and investments are valued using quoted prices that are readily and regularly available in the active market. The Company's Level 2 investments are valued using third-party pricing sources based on observable inputs, such as quoted prices for similar assets at the measurement date; or other inputs that are observable, either directly or indirectly. The following table summarizes, by major security type, the Company's assets that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy and where they are classified on the Consolidated Balance Sheets (in thousands): December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents Short-term (1) investments Cash $ 9,849 $ — $ — $ 9,849 $ 9,849 $ — Level 1 securities: Money market funds 3,499 — — 3,499 3,499 — U.S. treasury bonds 9,243 — (4 ) 9,239 — 9,239 Level 2 securities: Corporate bonds 4,935 — (6 ) 4,929 — 4,929 Agency bond 12,734 — (22 ) 12,712 — 12,712 Repurchase agreement 5,000 — — 5,000 5,000 — Total $ 45,260 $ — $ (32 ) $ 45,228 $ 18,348 $ 26,880 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents Short-term (1) investments Cash $ 8,504 $ — $ — $ 8,504 $ 8,504 $ — Level 1 securities: Money market funds 28,753 — — 28,753 28,753 — Level 2 securities: Corporate bonds 6,701 — (4 ) 6,697 — 6,697 Agency bonds 21,548 — (3 ) 21,545 — 21,545 Total $ 65,506 $ — $ (7 ) $ 65,499 $ 37,257 $ 28,242 (1) Contractual maturity due within one year.

Accounts Receivable

Accounts Receivable	12 Months Ended
	Dec. 31, 2017
Accounts Receivable, Net, Current [Abstract]
Accounts Receivable	Accounts Receivable Accounts receivable consisted of the following (in thousands): December 31, December 31, Total receivables $ 13,835 $ 15,356 Allowance for doubtful accounts and returns (635 ) (681 ) Accounts receivable, net $ 13,200 $ 14,675 Accounts receivable included unbilled receivable of $1.4 million and $2.5 million for the years ended December 31, 2017 and 2016 . Write-offs related to accounts receivable were approximately $92,000 for the year ended December 31, 2017 , $41,000 for the year ended December 31, 2016 and $88,000 for year ended December 31, 2015 . Summary of allowance for doubtful accounts and returns activity was as follows (in thousands): December 31, 2017 December 31, 2016 Beginning balance $ (681 ) $ (554 ) Provision for bad debts on trade receivables 15 (188 ) Other allowances (61 ) 20 Accounts receivable write offs 92 41 Ending balance $ (635 ) $ (681 )

Inventories

Inventories	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consisted of the following (in thousands): December 31, December 31, Raw Material $ 2,905 $ 3,331 Work in process 1,718 2,530 Finished goods 4,561 5,859 Total Inventories $ 9,184 $ 11,720 At December 31, 2017 and December 31, 2016 , inventories included write-downs of $0 and $0.2 million , respectively, related to units affected by the recall and sterilization capacity limitation.

Acquistion

Acquistion	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquistion	Acquisition On August 9, 2017, the Company completed the purchase of certain assets and assumed certain liabilities of Broad Peak Manufacturing, LLC (BPM), for approximately $6.4 million . Of the total purchase price paid, $5.8 million was in cash and $ 0.6 million of unregistered shares of common stock. The purchase was treated as a business combination as it met certain criteria stipulated in ASC 805 - Business Combinations. Prior to the acquisition, BPM provided substantially all of the polishing services for the Company’s femoral implant component. The Company expects the acquisition of the BPM assets will reduce the cost of polishing and improve overall gross margin. The Company completed the BPM purchase price allocation. Of the total purchase price, approximately $2.2 million related to earn out provisions tied to certain employee retention by the Company and achieving certain cost targets that was paid into an escrow account. An additional $0.7 million could be earned by BPM if the actual cost targets are exceeded. Alternatively, the earn out provisions could be paid back to the Company if the employee retention and cost targets are not achieved. The Company's best estimate of the range of possibilities is that none of the consideration in connection with employee retention or cost targets will be returned and that less than $0.1 million of additional consideration will be earned as a result of exceeding the cost targets. These estimates are based on various considerations regarding the employee retention and the streamlined cost structure associated with the polishing processes. For the year-ended December 31, 2017, the Company's estimate of contingent consideration did not require an adjustment to the variable consideration. Of the total purchase price of $6.4 million , $0.4 million was attributed to property and equipment, $6.0 million was attributed to goodwill and less than $0.1 million to other net assets acquired. Goodwill is primarily attributable to the future cost savings expected to arise after the acquisition and is deductible for tax purposes. The acquisition of BPM is strategically significant in reducing the manufacturing costs for the Company, however at the time of the acquisition and on December 31, 2017, the Company concluded that historical results of the BPM both individually and in the aggregate, were immaterial to the Company’s consolidated financial results and therefore additional pro-forma disclosures are not presented.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Property and Equipment Property and equipment consisted of the following (in thousands): Estimated Useful Life (Years) December 31, December 31, Equipment 5-7 $ 19,331 $ 16,651 Furniture and fixtures 5-7 955 414 Computer and software 3 7,877 7,027 Leasehold improvements 2-8 1,830 1,294 Total property and equipment 29,993 25,386 Accumulated depreciation (13,479 ) (10,302 ) Property and equipment, net $ 16,514 $ 15,084 Depreciation expense related to property and equipment was $3.4 million , $2.9 million and $2.4 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. In 2017, the Company recorded an impairment of $0.8 million related to the discontinuance of a software capital project. In 2016, the Company recorded $0.1 million in impairment charges in connection with certain manufacturing equipment previously purchased that was returned to the seller in exchange for a credit toward future purchase, which value is less than the book value of the equipment.

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2017
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets	Intangible Assets The components of intangible assets consisted of the following (in thousands): Estimated Useful Life (Years) December 31, 2017 December 31, 2016 Developed technology 10 $ 979 $ 979 Accumulated amortization (783 ) (681 ) Developed technology, net 196 298 License agreements 10 — 1,508 Accumulated amortization — (1,060 ) License technology, net — 448 Acquired favorable lease 5 15 — Accumulated amortization (1 ) — Acquired favorable lease, net 14 — Intangible assets, net $ 210 $ 746 The Company recognized amortization expense of $0.2 million in the years ended December 31, 2017 , 2016 and 2015 . The weighted-average remaining life of total amortizable intangible assets is 2.2 years for the developed technology and favorable lease asset. In the year ended December 31, 2017, the Company recorded an impairment charge of $0.3 million in general and administration expense in connection with the termination of the license agreements. See “Note B —Summary of Significant Accounting Policies” to the financial statements in this Annual Report on Form 10-K for a full description of the impairment charges related to intellectual property rights licensed as part of the ImaTx spin-out transaction in 2004. The estimated future aggregated amortization expense for intangible assets owned as of December 31, 2017 consisted of the following (in thousands): Amortization expense 2018 $ 101 2019 101 2020 3 2021 3 2022 2 $ 210

Accrued Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2017
Accrued Liabilities and Other Liabilities [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses consisted of the following (in thousands): December 31, 2017 December 31, 2016 Accrued employee compensation $ 2,989 $ 4,037 Deferred rent 115 101 Accrued legal expense 1,231 710 Accrued consulting expense 115 104 Accrued vendor charges 912 1,396 Accrued revenue share expense 968 992 Accrued clinical trial expense 196 256 Accrued other 1,194 896 $ 7,720 $ 8,492

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases - Real Estate The Company maintains its corporate headquarters in a leased building located in Billerica, Massachusetts. The Company moved its corporate headquarters from Bedford, Massachusetts in April 2017. The Company maintains its manufacturing facilities in leased buildings located in Wilmington, Massachusetts and Wallingford, Connecticut. The Billerica facility is leased under a long-term, non-cancellable lease that is scheduled to expire in October 2025. The Company leased the Bedford facility under a long-term, non-cancellable sublease that was set to expire in April 2017. In April 2017, the Company and the landlord of the Bedford facility agreed to a holdover of 30 days beyond the lease termination through May 31, 2017, which subsequently expired. The Company leases its Wilmington, Massachusetts facility under a long-term, non-cancellable lease that commenced in April 2015 and will expire in July 2022 (the "Wilmington Lease"). The Company also rents a satellite facility under short-term non-cancellable operating lease. On July 25, 2016, the Company entered into an amendment to the Wilmington Lease. Pursuant to the amendment, the Company exercised an option in its current lease to rent an additional 18,223 square feet of space adjacent to the Company’s existing premises. The Company took possession of the additional space in April 2017. The Company has a right to extend the term for one additional five -year period following termination of the lease in March 2022. The initial base rental rate for the additional space is $0.2 million annually, subject to 2% annual increases until the expiration of the initial term. On August 9, 2017, the Company entered into a lease for 4,099 square feet of space in Wallingford, Connecticut which houses the polishing and passivation processes. The lease term is five years with the option to extend for two additional years beyond the original term and an additional three years past the first extension term. The future minimum rental payments under the Company’s non-cancellable operating leases for real estate as of December 31, 2017 were as follows (in thousands): Year Minimum lease Payments 2018 $ 1,521 2019 1,558 2020 1,595 2021 1,633 2022 1,397 2023-2025 2,939 $ 10,643 Rent expense of $1.7 million for the year ended December 31, 2017 , $1.5 million for the year ended December 31, 2016 and $1.6 million for the year ended December 31, 2015 was charged to operations, respectively. The Company’s real estate operating lease agreements contain scheduled rent increases, which are being amortized over the terms of the agreements using the straight-line method. Deferred rent was $0.8 million as of December 31, 2017 , $0.3 million as of December 31, 2016 and $0.4 million and December 31, 2015 . Deferred rent is included in accrued expenses and other long-term liabilities. License and revenue share agreements Revenue share agreements The Company is party to revenue share agreements with certain past and present members of its scientific advisory board under which these advisors agreed to participate on its scientific advisory board and to assist with the development of the Company’s customized implant products and related intellectual property. These agreements provide that the Company will pay the advisor a specified percentage of the Company’s net revenue, ranging from 0.1 % to 1.33 %, with respect to the Company’s products on which the advisor made a technical contribution or, in some cases, which the Company covered by a claim of one of its patents on which the advisor is a named inventor. The specific percentage is determined by reference to product classifications set forth in the agreement and is tiered based on the level of net revenue collected by the Company on such product sales. The Company’s payment obligations under these agreements typically expire a fixed number of years after expiration or termination of the agreement, but in some cases expire on a product-by-product basis or expiration of the last to expire of the Company’s patents where the advisor is a named inventor that claims the applicable product. Philipp Lang, M.D., one of the Company’s directors and former Chief Executive Officer, joined the Company’s scientific advisory board in 2004 prior to becoming an employee. The Company first entered into a revenue share agreement with Dr. Lang in 2008 when he became the Company’s Chief Executive Officer. In 2011, the Company entered into an amended and restated revenue share agreement with Dr. Lang. Under this agreement, the specified percentage of the Company’s net revenue payable to Dr. Lang ranges from 0.875 % to 1.33 % and applies to all of the Company’s current products, including the Company’s iUni, iDuo, iTotal CR, and iTotal PS products, as well as certain other knee, hip and shoulder replacement products and related instrumentation the Company may develop in the future. The Company’s payment obligations under this agreement expire on a product-by-product basis on the last to expire of the Company’s patents on which Dr. Lang is named an inventor that claim the applicable product. These payment obligations survived the termination of Dr. Lang’s employment with the Company. The Company incurred revenue share expense paid to Dr. Lang of $1.0 million , $1.0 million and $0.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. The Company incurred aggregate revenue share expense including all amounts payable under the Company’s scientific advisory board and Dr. Lang revenue share agreements of $3.7 million during the year ended December 31, 2017 , representing 4.8% of product revenue, $3.5 million during the year ended December 31, 2016 , representing 4.4% of product revenue, and $3.2 million during the year ended December 31, 2015 , representing 5.0% of product revenue. Revenue share expense is included in research and development. See “Note L—Related Party Transactions” for further information regarding the Company’s arrangement with Dr. Lang. Other obligations In the ordinary course of business, the Company is a party to certain non-cancellable contractual obligations typically related to product royalty and research and development. The Company accrues a liability for such matters when it is probable that future expenditures will be made and such expenditures can be reasonably estimated. The following table summarizes the Company's contractual obligations as of the year ended December 31, 2017 (in thousands): Payment Due by Period Total Less than 1 year Years 1 to 3 Years 3 to 5 After 5 years Contractual Obligations (1)(2) $ 1,435 $ 378 $ 756 $ 301 $ — (1) Represents amounts payable under our product royalty agreement, operating leases for office equipment, and a software development collaboration project with a remaining term in excess of one year. (2) This table does not include: (a) revenue share obligations to past and present members of our scientific advisory board and one of our directors, as the amounts of such payments are not known with certainty; and (b) contracts that are entered into in the ordinary course of business that are not material in the aggregate in any period presented above. See "—Revenue share agreements" for a description of our revenue share arrangements. There have been no contingent liabilities requiring accrual at December 31, 2017 or December 31, 2016 . Legal proceedings In the ordinary course of the Company's business, the Company is subject to litigation, claims and administrative proceedings on a variety of matters, including patent infringement, product liability, securities-related claims, and other claims in the United States and in other countries where the Company sells its products. An estimate of the possible loss or range of loss as a result of any of these matters cannot be made; however, management does not believe that these matters, individually or in the aggregate, are material to its financial condition, results of operations or cash flows. On February 29, 2016, the Company filed a lawsuit against Smith & Nephew, Inc. (“Smith & Nephew”) in the United States District Court for the District of Massachusetts Eastern Division, and the Company amended its complaint on June 13, 2016 (the "Smith & Nephew Lawsuit"). The Smith & Nephew Lawsuit alleges that Smith & Nephew’s Visionaire® patient-specific instrumentation as well as the implants systems used in conjunction with the Visionaire instrumentation infringe nine of the Company's patents, and it requests, among other relief, monetary damages for willful infringement, enhanced damages and a permanent injunction. On May 27, 2016, Smith & Nephew filed its answer and counterclaims in response to the Company's lawsuit, which it subsequently amended on July 22, 2016. Smith & Nephew denied that its Visionaire® patient-specific instrumentation as well as the implants systems used in conjunction with the Visionaire instrumentation infringe the patents asserted by the Company in the lawsuit. It also alleged two affirmative defenses: that the Company's asserted patents are invalid and that the Company is barred from relief under the doctrine of laches. In addition, Smith & Nephew asserted a series of counterclaims, including counterclaims seeking declaratory judgments that Smith & Nephew’s accused products do not infringe the Company's patents and that the Company's patents are invalid. Smith & Nephew also alleged that ConforMIS infringes ten patents owned or exclusively licensed by Smith & Nephew: two of those patents Smith & Nephew alleges are infringed by the Company's iUni and iDuo products; three of those patents Smith & Nephew alleges are infringed by the Company's iTotal products; and five of those patents Smith & Nephew licenses from Kinamed, Inc. of Camarillo, California and alleges are infringed by the Company's iUni, iDuo and iTotal products. Due to Smith & Nephew’s licensing arrangement with Kinamed, Kinamed was named as a party to the lawsuit. Smith & Nephew and Kinamed requested, among other relief, monetary damages for willful infringement, enhanced damages and a permanent injunction. On March 9, 2017, the Court entered a stipulation of dismissal by the parties that dismissed from the lawsuit eight patents asserted by Smith & Nephew, including the patents involving Kinamed and two patents asserted by ConforMIS. Between September 21, 2016 and March 1, 2017, Smith & Nephew filed sixteen petitions with the United States Patent & Trademark Office (“USPTO”) requesting Inter Partes Review of the nine patents that the Company asserted against Smith & Nephew in the lawsuit. In its petitions, Smith & Nephew alleged that the Company's patents are obvious in light of certain prior art. As of October 31, 2017, the USPTO decided to institute IPR proceedings with respect to seven of the petitions; decided to deny the requests for IPR with respect to seven of the petitions; and, with respect to the remaining two petitions, decided to institute IPR proceedings for certain of the subject patent claims and to deny the requests for the remaining subject patent claims. In total, the USPTO instituted IPR proceedings for some or all of the subject patent claims in six of the patents in the Smith & Nephew lawsuit ( five patents that are currently asserted, and one of the patents that was voluntarily dismissed from the lawsuit), and denied the petitions for all subject claims in three of the patents ( two patents that are currently asserted and one of the patents that was voluntarily dismissed from the lawsuit). Smith & Nephew filed requests for rehearing in three of the petitions that were either partially or completely denied and filed requests for reexamination of two of the patents for which no IPR was instituted. The requests for rehearing were denied. On January 27, 2017, Smith & Nephew filed a motion seeking a stay of the Smith & Nephew Lawsuit until any requested IPRs are resolved, and the Company filed an opposition to that motion. On April 27, 2017, the Court stayed certain aspects of the proceedings and indicated that it will make a final decision on the motion to stay after the USPTO has decided more of the petitions for IPR. The Company is presently unable to predict the outcome of the motion to stay the proceedings, the instituted IPRs, the reexaminations, or the Smith & Nephew Lawsuit or to reasonably estimate a range of potential losses, if any, related thereto. An adverse outcome of some or all of the IPR proceedings, the reexaminations, or the Smith & Nephew Lawsuit could have a material adverse effect on the Company's business, financial condition or results of operations. Legal costs associated with legal proceedings are accrued as incurred. Indemnifications In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. In accordance with its bylaws, the Company has indemnification obligations to its officers and directors for certain events or occurrences, subject to certain limits, while they are serving at the Company’s request in such capacity. There have been no claims to date and the Company has a director and officer insurance policy that enables it to recover a portion of any amounts paid for future claims.

Debt and Notes Payable

Debt and Notes Payable	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt and Notes Payable	Debt and Notes Payable Long-term debt consisted of the following (in thousands): December 31, 2017 December 31, 2016 Oxford Finance, LLC, Term A Loan $ 15,000 $ — Oxford Finance, LLC, Term B Loan 15,000 30,000 — Less unamortized debt issuance costs (333 ) — Long-term debt, less debt issuance costs $ 29,667 $ — Principal payments due as of December 31, 2017 consisted of the following (in thousands): Principal 2018 $ — 2019 — 2020 13,750 2021 15,000 2022 1,250 Total $ 30,000 2017 Secured Loan Agreement On January 6, 2017, the Company entered into a senior secured $50 million loan and security agreement with Oxford (the "2017 Secured Loan Agreement"). Through the 2017 Secured Loan Agreement, the Company initially accessed $15 million of borrowings (the "Term A Loan"), with an additional $15 million of borrowings (the "Term B Loan"), and $20 million of borrowings, available to borrow, at its option, through December 2017 and June 2018, respectively, subject to the satisfaction of certain revenue milestones and customary drawdown conditions, which the Company does not expect will be satisfied by the end of June 2018. On March 9, 2017, the 2017 Secured Loan Agreement with Oxford was amended to include an additional revenue milestone in order for the Company to drawdown the second and third tranches. On June 30, 2017, the 2017 Secured Loan Agreement was further amended to, among other things, amend the period during which the Company was able to borrow the second term loan under the 2017 Secured Loan Agreement, and also to amend the associated financial covenants of the Company. Amending the 2017 Secured Loan Agreement made the Term B Loan available to the Company through the earlier of (i) June 30, 2017, or (ii) an event of default under the 2017 Secured Loan Agreement. Concurrently, on June 30, 2017, the Company drew down Term B Loan. Except as modified by the amendment, all terms and conditions of the 2017 Secured Loan Agreement remain in full force and effect. The proceeds of the Term B Loan will be used to fund the Company’s ongoing working capital needs. The 2017 Secured Loan Agreement is secured by substantially all of the Company’s personal property other than the Company’s intellectual property. Under the terms of the 2017 Secured Loan Agreement, the Company cannot grant a security interest in its intellectual property to any other party. The term loans under the 2017 Secured Loan Agreement bears interest at a floating annual rate calculated at the greater of 30 day LIBOR or 0.53% , plus 6.47% . The Company is required to make monthly interest only payments in arrears commencing on the second payment date following the funding date of each term loan, and continuing on the payment date of each successive month thereafter through and including the payment date immediately preceding the amortization date of February 1, 2020. Commencing on the amortization date, and continuing on the payment date of each month thereafter, the Company is required to make consecutive equal monthly payments of principal of each term loan, together with accrued interest, in arrears, to Oxford. All unpaid principal, accrued and unpaid interest with respect to each term loan, and a final payment in the amount of 5.0% of the amount of loans advanced, is due and payable in full on the term loan maturity date. The 2017 Secured Loan Agreement has a term of five years and matures on January 1, 2022. At the Company’s option, the Company may prepay all, but not less than all, of the term loans advanced by Oxford under the 2017 Secured Loan Agreement, subject to a prepayment fee and an amount equal to the sum of all outstanding principal of the term loans plus accrued and unpaid interest thereon through the prepayment date, a final payment, plus all other amounts that are due and payable, including Oxford's expenses and interest at the default rate with respect to any past due amounts. The 2017 Secured Loan Agreement also includes events of default, the occurrence and continuation of which could cause interest to be charged at the rate that is otherwise applicable plus 5.0% and would provide Oxford, as collateral agent with the right to exercise remedies against us and the collateral securing the Secured Loan Agreement, including foreclosure against assets securing the 2017 Secured Loan Agreement, including the Company’s cash. These events of default include, among other things, the Company’s failure to pay any amounts due under the 2017 Secured Loan Agreement, a breach of covenants under the 2017 Secured Loan Agreement, including, among other customary debt covenants, achieving certain revenue levels and limiting the amount of cash and cash equivalents held by the Company's foreign subsidiaries, the Company’s insolvency, a material adverse change, the occurrence of any default under certain other indebtedness in an amount greater than $500,000 , one or more judgments against the Company in an amount greater than $500,000 , a material adverse change with respect to any governmental approval and any delisting event. As of December 31, 2017 , the Company was not in breach of covenants under the 2017 Secured Loan Agreement.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Vertegen In April 2007, the Company entered into a license agreement with Vertegen, Inc., or Vertegen, which was amended in May 2015 (the “Vertegen Agreement”). Vertegen is an entity that is wholly owned by Dr. Lang, the Company’s former Chief Executive Officer. Under the Vertegen Agreement, Vertegen granted the Company an exclusive, worldwide license under specified Vertegen patent rights and related technology to make, use and sell products and services in the fields of diagnosis and treatment of articular disorders and disorders of the human spine. The Company may sublicense the rights licensed to it by Vertegen. The Company is required to use commercially reasonable efforts, at its sole expense, to prosecute the patent applications licensed to the Company by Vertegen. Pursuant to the Vertegen Agreement, the Company is required to pay Vertegen a 6% royalty on net sales of products covered by the patents licensed to the Company by Vertegen, the subject matter of which is directed primarily to spinal implants, and any proceeds from the Company enforcing the patent rights licensed to the Company by Vertegen. Such 6% royalty rate will be reduced to 3% in the United States during the five -year period following the expiration of the last-to-expire applicable patent in the United States and in the rest of the world during the five -year period following the expiration of the last-to-expire patent anywhere in the world. The Company has not sold any products subject to this agreement and has paid no royalties under this agreement. The Company has cumulatively paid approximately $150,000 in expenses as of December 31, 2017 and 2016 , and $140,000 as of December 31, 2015 , in connection with the filing and prosecution of the patent applications licensed to the Company by Vertegen. The Vertegen Agreement may be terminated by the Company at any time by providing notice to Vertegen. In addition, Vertegen may terminate the Vertegen Agreement in its entirety if the Company is in material breach of the agreement, and the Company fails to cure such breach during a specified period. Revenue share agreements As described in Note J, the Company is a party to certain agreements with advisors to participate as a member of the Company’s scientific advisory board. In September 2011, the Company entered into an amended and restated revenue share agreement with Philipp Lang, M.D., one of the Company’s directors and former Chief Executive Officer, which amended and restated a similar agreement entered into in 2008 when Dr. Lang stepped down as chair of the Company’s scientific advisory board and became the Company’s Chief Executive Officer. This agreement provides that the Company will pay Dr. Lang a specified percentage of our net revenue, ranging from 0.875 % to 1.33 %, with respect to all of our current and planned products, including the Company’s iUni, iDuo, iTotal CR, and iTotal PS products, as well as certain other knee, hip and shoulder replacement products and related instrumentation the Company may develop in the future. The specific percentage is determined by reference to product classifications set forth in the agreement and is tiered based on the level of net revenue collected by the Company on such product sales. The Company’s payment obligations expire on a product-by-product basis on the last to expire of the Company’s patents on which Dr. Lang is a named inventor that claim the applicable product. These payment obligations survived the termination of Dr. Lang’s employment with the Company. The Company incurred revenue share expense paid to Dr. Lang of $1.0 million , $1.0 million and $0.8 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Stockholders’ Equity Common stock Common stockholders are entitled to dividends as and when declared by the board of directors, subject to the rights of holders of all classes of stock outstanding having priority rights as to dividends. There have been no dividends declared to date. Summary of common stock activity was as follows: Shares Outstanding December 31, 2015 41,110,127 Issuance of common stock - option & warrant exercises 1,485,401 Issuance of restricted common stock 804,019 Outstanding December 31, 2016 43,399,547 Issuance of common stock - option 535,734 Issuance of restricted common stock 1,195,196 Issuance of common stock - ATM offering 228,946 Issuance of common stock - BPM acquisition 169,096 Outstanding December 31, 2017 45,528,519 Preferred stock The Company’s Restated Certificate of Incorporation authorizes the Company to issue 5,000,000 shares of preferred stock, $0.00001 par value, all of which is undesignated. No shares were issued and outstanding at December 31, 2017 and December 31, 2016 . Demand registration rights In conjunction with the IPO, the Company entered into an Amended and Restated Information and Registration Rights Agreement effective June 29, 2015 (the “Registration Rights Agreement”), which provided, among other things, registration rights to certain investors that had held the Company's preferred stock prior to the IPO. Subject to specified limitations set forth in a registration rights agreement, at any time, the holders of at least 25% of the then outstanding registrable shares may at any time demand in writing that the Company register all or a portion of the registrable shares under the Securities Act on a Form other than Form S-3 for an offering of at least 20% of the then outstanding registrable shares or a lesser percentage of the then outstanding registrable shares provided that it is reasonably anticipated that the aggregate offering price would exceed $20 million . The Company is not obligated to file a registration statement pursuant to these rights on more than two occasions. Additionally, after such time as the Company became eligible to use Form S-3, subject to specified limitations set forth in the registration rights agreement, the holders of at least 25% of the then outstanding registrable shares became able to at any time demand in writing that the Company register all or a portion of the registrable shares under the Securities Act on Form S-3 for an offering of at least 25% of the then outstanding registrable shares having an anticipated aggregate offering price to the public, net of selling expenses, of at least $5 million (a “Resale Registration Statement”). The Company is not obligated to effect a registration pursuant to a Resale Registration Statement on more than one occasion. Incidental registration rights If, the Company proposes to file a registration statement in connection with a public offering of its common stock , subject to certain exceptions, the holders of registrable shares are entitled to notice of registration and, subject to specified exceptions, including market conditions, the Company will be required, upon the holder’s request, to register their then held registrable shares. Warrants The Company also issued warrants to certain investors and consultants to purchase shares of the Company’s preferred stock and common stock. Based on the Company’s assessment of the warrants granted in 2013 and 2014 relative to ASC 480, Distinguishing Liabilities from Equity , the warrants are classified as equity. No warrants were issued in the years ended December 31, 2017 and 2016 . According to ASC 480, an entity shall classify as a liability any financial instrument, other than an outstanding share, that, at inception, both a) embodies an obligation to repurchase the issuer’s equity shares, or is indexed to such obligation and b) requires or may require the issuer to settle the obligation by transferring assets. The warrants do not contain any provision that requires the Company to repurchase the shares and are not indexed to such an obligation. The warrants also do not require the Company to settle by transferring assets. All warrants were exercisable immediately upon issuance. Common stock warrants The Company also issued warrants to certain investors and consultants to purchase shares of common stock. Warrants to purchase 28,926 shares of common stock were outstanding as of December 31, 2017 and 171,783 shares of common stock were outstanding as of December 31, 2016 . Outstanding warrants are currently exercisable with varying exercise expiration dates from 2020 through 2024. Summary of common stock warrant activity was as follows: Number of Warrants Weighted Average Exercise Price Per Share Number of Warrants Exercisable Weighted Average Price Per Share Weighted Average Contractual Life Outstanding December 31, 2015 751,779 $ 10.30 751,779 $ 10.30 1.33 Exercised (166,665 ) 9.00 (166,665 ) 9.00 — Cancelled/expired (413,331 ) — (413,331 ) — — Outstanding December 31, 2016 171,783 $ 7.47 171,783 $ 7.47 1.62 Cancelled/expired (142,857 ) 7.00 (142,857 ) 7.00 — Outstanding December 31, 2017 28,926 $ 9.80 28,926 $ 9.80 5.66 Stock option plans In June 2004, the Company authorized the adoption of the 2004 Stock Option and Incentive Plan (the “2004 Plan”). Under the 2004 Plan, options were granted to persons who were, at the time of grant, employees, officers, or directors of, or consultants or advisors to, the Company. The 2004 Plan provided for the granting of non-statutory options, incentive options, stock bonuses, and rights to acquire restricted stock. The option price at the date of grant was determined by the Board of Directors and, in the case of incentive options, could not be less than the fair market value of the common stock at the date of grant, as determined by the Board of Directors. Options granted under the 2004 Plan generally vest over a period of four years and are set to expire ten years from the date of grant. In February 2011, the Company terminated the 2004 Plan and all options outstanding under it were transferred to the 2011 Stock Option/Stock Issuance Plan (the “2011 Plan”). In February 2011, the Company authorized the adoption of the 2011 Plan. The 2011 Plan is divided into two separate equity programs, Option Grant Program and Stock Issuance Program. Per the 2011 Plan, options can be granted to persons who are, at the time, employees, officers, or directors of, or consultants or advisors to, the Company. The 2011 Plan provides for the granting of non-statutory options, incentive options and common stock. The price at the date of grant is determined by the Board of Directors and, in the case of incentive options and common stock, cannot be less than the fair market value of the common stock at the date of grant, as determined by the Board of Directors. Options granted under the 2011 Plan generally vest over a period of four years and expire ten years from the date of grant. In June 2015, the Company terminated the 2011 Plan and all options outstanding under it were transferred to the 2015 Stock Incentive Plan (the “2015 Plan”). The 2015 Plan provides for the grant of incentive stock options, nonstatutory stock options, stock appreciation rights, restricted stock awards, restricted stock units and other stock-based awards. The number of shares of our common stock that will be reserved for issuance under the 2015 Plan is the sum of: (1) 2,000,000 ; plus (2) the number of shares equal to the sum of the number of shares of our common stock then available for issuance under the 2011 Plan and the number of shares of our common stock subject to outstanding awards under the 2011 Plan or under the 2004 Plan that expire, terminate or are otherwise surrendered, canceled, forfeited or repurchased by us at their original issuance price pursuant to a contractual repurchase right; plus (3) an annual increase, to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2016 and continuing until, and including, the fiscal year ending December 31, 2025, equal to the least of (a) 3,000,000 shares of our common stock, (b) 3% of the number of shares of our common stock outstanding on the first day of such fiscal year and (c) an amount determined by the Board. Our employees, officers, directors, consultants and advisors will be eligible to receive awards under the 2015 Plan. Incentive stock options, however, may only be granted to our employees. Options and restricted stock awards granted under the 2015 Plan generally vest over a period of four years and expire ten years from the date of grant. As of December 31, 2017 , 1,051,471 shares of common stock were available for future issuance under the 2015 Plan. Activity under all stock option plans was as follows: Number of Options Weighted Average Exercise Price per Share Aggregate Intrinsic Value (In Thousands) Outstanding December 31, 2014 5,355,567 $ 4.87 Granted 403,086 12.20 Exercised (383,458 ) 2.10 $ 5,691 Expired (30,876 ) 5.97 Cancelled/Forfeited (95,990 ) 7.42 Outstanding December 31, 2015 5,248,329 $ 5.56 $ 61,741 Granted 179,178 8.78 Exercised (1,467,692 ) 2.78 8,219 Expired (81,251 ) 9.70 Cancelled/Forfeited (88,524 ) 9.93 Outstanding December 31, 2016 3,790,040 $ 6.60 $ 8,547 Granted 963,350 4.95 Exercised (535,734 ) 3.94 1,688 Expired (466,210 ) 7.17 Cancelled/Forfeited (123,451 ) 6.54 Outstanding December 31, 2017 3,627,995 $ 6.48 $ 96 Total vested and exercisable 2,696,151 $ 6.66 $ 96 The total fair value of stock options that vested during the year ended December 31, 2017 was $1.6 million . The weighted average remaining contractual term for the total stock options outstanding was 5.83 years at December 31, 2017 . The weighted average remaining contractual term for the total stock options vested and exercisable was 4.69 years at December 31, 2017 . Restricted common stock award activity under the plan was as follows: Number of Shares Weighted Average Fair Value Unvested December 31, 2014 — $ — Granted 174,530 22.31 Unvested December 31, 2015 174,530 22.31 Granted 873,589 8.61 Vested (66,839 ) 17.72 Forfeited (69,570 ) 11.83 Unvested December 31, 2016 911,710 $ 10.32 Granted 1,421,364 4.20 Vested (767,785 ) 7.11 Forfeited (226,168 ) 7.36 Unvested December 31, 2017 1,339,121 $ 6.06 The total fair value of restricted common stock awards that vested during the year ended December 31, 2017 was $ 5.5 million . Stock-based compensation The Company uses the Black-Scholes option pricing model to determine the fair value of stock options. The determination of the fair value of stock-based payment awards on the date of grant using a pricing model is affected by the value of the Company’s common stock as well as assumptions regarding a number of complex and subjective variables. The valuation of the Company’s common stock prior to the IPO was performed with the assistance of an independent third-party valuation firm using a methodology that includes various inputs including the Company’s historical and projected financial results, peer company public data and market metrics, such as risk-free interest and discount rates. As the valuations included unobservable inputs that were primarily based on the Company’s own assumptions, the inputs were considered level 3 inputs within the fair value hierarchy. The weighted average fair value of options granted was $2.49 for the year ended December 31, 2017 , $4.46 for the year ended December 31, 2016 and $5.52 for the year ended December 31, 2015 . The fair value of options at date of grant was estimated using the Black-Scholes option pricing model, based on the following assumptions: Years Ended December 31, 2017 2016 2015 Risk-free interest rate 2.10% - 2.30% 1.98% 1.37% - 1.77% Expected term (in years) 6.02 - 6.25 6.25 5.47 - 6.45 Dividend yield —% —% —% Expected volatility 51.00% - 53.00% 51.00% 49.00% - 50.00% Risk-free interest rate. The risk-free interest rate is based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected term on the options. Expected term. The expected term of stock options represents the period the stock options are expected to remain outstanding and is based on the “SEC Shortcut Approach” as defined in “Share-Based Payment” (SAB 107) ASC 718-10-S99, “Compensation—Stock Compensation—Overall—SEC Materials ,” which is the midpoint between the vesting date and the end of the contractual term. With certain stock option grants, the exercise price may exceed the fair value of the common stock. In these instances, the Company adjusts the expected term accordingly. Dividend yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future, and, therefore, used an expected dividend yield of zero in the valuation model. Expected volatility. Expected volatility measures the amount that a stock price has fluctuated or is expected to fluctuate during a period. The Company does not have sufficient history of market prices of its common stock as it is a newly public company. Therefore, the Company estimates volatility using historical volatilities of similar public entities. Forfeitures. Effective January 1, 2017, the Company elected to change its accounting policy to recognize forfeitures as they occur in accordance with ASU 2016-09, "Compensation - Stock Compensation". Prior to this election, the Company recognized share-based compensation net of estimated forfeitures over the vesting period of the respective grant. Stock-based compensation expense was $6.0 million , $5.3 million and $3.6 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Stock-based compensation expense was calculated based on awards ultimately expected to vest. To date, the amount of stock-based compensation capitalized as part of inventory was not material. The following is a summary of stock-based compensation expense (in thousands): Years Ended December 31, 2017 2016 2015 Cost of revenue $ 441 $ 333 $ 239 Sales and marketing 919 1,197 730 Research and development 1,920 1,466 784 General and administrative 2,768 2,328 1,854 $ 6,048 $ 5,324 $ 3,607 At December 31, 2017 , the Company had $2.6 million of total unrecognized compensation expense for options that will be recognized over a weighted average period of 3.11 years. At December 31, 2017 , the Company had $ 6.5 million of total unrecognized compensation expense for restricted awards recognized over a weighted average period of 2.94 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company files U.S. federal and state tax returns as well as foreign income tax returns. The Company has accumulated significant losses since its inception in 2004. For financial reporting purposes, income (loss) before income taxes for the years ended December 31, 2017 , 2016 and 2015 include the following components (in thousands): Years ended December 31, 2017 2016 2015 Loss before income taxes: U.S. $ (53,274 ) $ (51,576 ) $ (50,155 ) Non‑U.S. (144 ) (5,949 ) (7,050 ) $ (53,418 ) $ (57,525 ) $ (57,205 ) Significant components of the provision for income taxes for the years ended December 31, 2017 , 2016 and 2015 were as follows (in thousands): Years ended December 31, 2017 2016 2015 Current: Federal $ — $ — $ — State — — — Foreign 125 63 41 125 63 41 Deferred: Federal 31 — — State 6 — — Foreign — — — 37 — Total $ 162 $ 63 $ 41 The Company accounts for income taxes under FASB ASC 740 Accounting for Income Taxes . Deferred tax assets and liabilities are determined based upon differences between financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse. A reconciliation of the income tax expense (benefit) at the statutory federal income tax rate as reflected in the financial statements was as follows: Years ended December 31, 2017 2016 2015 Tax at U.S. statutory rate (34.00 )% (34.00 )% (34.00 )% State taxes, net of federal benefits (3.12 ) (2.70 ) (2.27 ) Permanent items 1.96 0.42 1.52 Tax credit (1.35 ) (1.06 ) (0.85 ) Change in valuation allowance (54.85 ) 33.95 31.07 Foreign rate differential (0.17 ) 1.04 1.68 Rate change 90.78 (0.06 ) 0.01 Uncertain tax positions 0.41 2.06 2.21 Other 0.64 0.46 0.70 0.30 % 0.11 % 0.07 % Deferred income taxes reflect the net tax effects of temporary differences between the carrying amount of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. On December 22, 2017, the Tax Act was signed into law. The new law did not have a significant impact on the Company’s consolidated financial statements for the year ended December 31, 2017 because it maintains a valuation allowance on the majority of its net operating losses and other deferred tax assets. However, the reduction of the U.S. federal corporate tax rate from 35% to 21% resulted in increases to the amounts reflected “Provision for (benefit from) income taxes attributable to valuation allowances” and “Rate change” captions for the year ended December 31, 2017 in the Company’s tax reconciliation table above compared to those amounts disclosed for the years ended December 31, 2016 and 2015. Significant components of the Company’s deferred tax assets (liabilities) consisted of the following (in thousands): Years ended December 31, 2017 2016 Deferred tax assets: Federal and state net operating loss carryforwards $ 90,437 $ 115,719 Foreign net operating loss carryforwards 2,561 2,561 Accrued expenses 157 280 Credits 6,055 5,091 Deferred revenue 1,068 1,709 Stock compensation expense 1,805 2,946 Other 2,111 2,757 Total deferred tax assets 104,194 131,063 Valuation allowance (103,430 ) (130,005 ) Net deferred tax assets 764 1,058 Deferred tax liabilities: Fixed assets (664 ) (841 ) Intangibles (134 ) (217 ) Other (3 ) — Net deferred tax liabilities (801 ) (1,058 ) Net deferred tax liabilities $ (37 ) $ — A valuation allowance is required to reduce the deferred tax assets reported if, based on weight of evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized. After consideration of all of the evidence, both positive and negative, the Company determined that a $103.4 million valuation allowance at December 31, 2017 was necessary to reduce the deferred tax assets to the amount that will more likely than not be realized. The change in the valuation allowance for the current year was $26.6 million . The Company provided a valuation allowance for the full amount, with the exception of the naked credit related to goodwill amortization, of its net deferred tax asset for all periods because realization of any future tax benefit cannot be sufficiently assured as the Company does not expect income in the near term. At December 31, 2017 , the Company had approximately $373.6 million of federal net operating loss carryforwards and approximately $198.9 million of state net operating loss carryforwards that if not utilized, will begin to expire in 2020 for federal tax purposes and continue to expire at various dates starting in 2018 for state tax purposes. The utilization of such net operating loss carryforwards and realization of tax benefits in future years depends predominantly upon having taxable income. Utilization of the NOL and credits may be subject to a substantial annual limitation due to ownership change limitations that have occurred or that could occur in the future, as required by Section 382 and Section 383 of the Code. These ownership changes may limit the amount of NOL that can be utilized annually to offset future taxable income and tax, respectively. In general, an “ownership change” as defined by Section 382 of the Code results from a transaction or series of transactions over a three‑year period resulting in an ownership change of more than 50 percentage points of the outstanding stock of a company by certain stockholders. The Company has completed a study to assess whether an ownership change has occurred or whether there have been multiple ownership changes since its formation. The results of this study indicated that the Company experienced ownership changes as defined by Section 382 of the Code. The Company has not identified NOLs or credits that, as a result of these restrictions, will expire unused. The Company also had foreign net operating losses of approximately $25.0 million as of December 31, 2017 , which may be available to offset future income recognized in the Federal Republic of Germany. The net operating losses in Germany have indefinite carryforward periods. The Company has adopted the accounting guidance related to uncertainty in income taxes. The total liability for unrecognized income tax benefits was approximately $5.1 million as of December 31, 2017 , $4.9 million as of December 31, 2016 and $3.7 million of December 31, 2015 . Of the total liability at December 31, 2017 and 2016 , $4.9 million and $4.8 million , respectively, were netted against deferred tax assets. The Company recognizes interest accrued and penalties, if applicable, related to unrecognized tax benefits in income tax expense. The Company does not expect any significant changes in the next 12 months. The reconciliation below summarized the Company's unrecognized tax benefits for the respective periods. These amounts primarily relate to transactions between the Company and its foreign subsidiaries, including accrued interest. Years ended December 31, 2017 2016 2015 Unrecognized tax benefits beginning of year $ 4,918 $ 3,730 $ 2,466 Gross change for current year positions 219 1,187 1,264 Unrecognized tax benefits end of the year $ 5,136 $ 4,918 $ 3,730 As of December 31, 2017 , the Company was open to examination in the U.S. federal and certain state jurisdictions for all of the Company’s tax years since the net operating losses may potentially be utilized in future years to reduce taxable income. The Company has been audited in Germany through 2015. The net operating loss carryforward from periods prior to 2015 may be utilized against taxable income in future periods and the net operating loss carryforward can be challenged at that time. At December 31, 2017 , foreign earnings, which were not significant, have been retained indefinitely by foreign subsidiary companies for reinvestment; therefore, no provision has been made for income taxes that would be payable upon the distribution of such earnings, and it would not be practicable to determine the amount of the related unrecognized deferred income tax liability. Upon repatriation of those earnings, in the form of dividends or otherwise, the Company would be subject to U.S. federal income taxes (subject to an adjustment for foreign tax credits) and withholding taxes payable to the various foreign countries. ASU No. 2016-09, "Compensation - Stock Compensation", was issued and adopted in January 2017. ASU 2016-09 eliminates APIC pools and requires excess tax benefits and tax deficiencies to be recorded in the income statement when the awards vest or are settled. In addition, modified retrospective adoption of ASU 2016-09 eliminates the requirement that excess tax benefits be realized (i.e., through a reduction in income taxes payable) before the Company can recognize them and therefore, it has accounted for a cumulative-effect adjustment of $7.7 million during the twelve months ended December 31, 2017 to record excess tax benefits. Since the Company has a full valuation allowance on all deferred taxes, this has no impact on retained earnings or the tax position of the Company. On December 22, 2017, the SEC staff issued SAB 118 to address the application of GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act. The Company has recognized the provisional tax impacts related to deemed repatriated earnings and the revaluation of deferred tax assets and liabilities and included these amounts in its consolidated financial statements for the year ended December 31, 2017. The Company has remeasured its deferred tax positions as of December 31, 2017 at the new enacted tax rate, resulting in a decrease to deferred tax assets in 2017 in the amount of $48.5 million . Since the Company has a valuation allowance on its deferred tax assets, there is no impact on current tax expense. For deferred taxes purposes, the Company recorded a benefit of approximately $19,000 due to the revaluation of the deferred tax liability hanging credit. These amounts are estimates and may change as U.S. treasury regulations and administrative guidance have not been finalized as of the date of this Form 10-K. The Company will continue to review the impact of these limitations as regulatory guidance is issued. The Company has an accumulated deficit from its foreign operations and does not have an associated liability from the repatriation tax on accumulated earnings in the Tax Act. The ultimate impact may differ from those provisional amounts, possibly materially, due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the Tax Act. The Company's accounting treatment is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018. As of December 31, 2017, foreign earnings, which were not significant, have been retained indefinitely by the Company's foreign subsidiaries for reinvestment.

Segment and Geographic Data

Segment and Geographic Data	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment and Geographic Data	Segment and Geographic Data The Company operates as one reportable segment as described in Note B to the Consolidated Financial Statements. The countries in which the Company has local revenue generating operations have been combined into the following geographic areas: the United States (including Puerto Rico), Germany and the rest of the world, which consists of Europe predominately (including the United Kingdom) and other foreign countries. Sales are attributable to a geographic area based upon the customer’s country of domicile. Net property, plant and equipment are based upon physical location of the assets. Geographic information consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Product Revenue United States $ 64,390 $ 62,366 $ 47,223 Germany 11,217 14,701 13,795 Rest of World 1,493 1,854 1,773 $ 77,100 $ 78,921 $ 62,791 December 31, 2017 2016 Property and equipment, net United States $ 16,424 $ 14,971 Rest of World 90 113 $ 16,514 $ 15,084

Employee Savings Plan

Employee Savings Plan	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Compensation and Employee Benefit Plans	Employee Savings Plan We have established an employee savings plan pursuant to Section 401(k) of the Internal Revenue Code. The plan allows participating employees to deposit into tax deferred investment accounts up to 80% of eligible earnings, subject to annual limits. We make contributions to the plan in an amount equal to 50% of elective deferrals on up to 4% of the participant’s eligible earnings. We contributed approximately $457,000 , $478,000 and $400,000 to the plan during the years ended December 31, 2017 , 2016 and 2015 , respectively.

Selected Quarterly Financial In

Selected Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Information	Selected Quarterly Financial Information (Unaudited) Three Months Ended December 31, 2017 September 30, 2017 June 30, 2017 March 31, 2017 Total revenue $ 20,751 $ 18,425 $ 18,484 $ 20,455 Gross profit 8,757 7,314 6,248 6,495 Net loss (11,858 ) (12,472 ) (12,090 ) (17,160 ) Net loss per share - basic and diluted $ (0.27 ) $ (0.29 ) $ (0.28 ) $ (0.40 ) Three Months Ended December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Total revenue $ 21,673 $ 18,643 $ 19,333 $ 20,250 Gross profit 8,045 5,998 6,001 6,663 Net loss (15,740 ) (12,762 ) (14,052 ) (15,034 ) Net loss per share - basic and diluted $ (0.37 ) $ (0.31 ) $ (0.34 ) $ (0.37 )

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events 2018 COMMON STOCK OFFERING On January 29, 2018, the Company closed an offering of its common stock off of the Shelf Registration Statement and issued and sold 15,333,333 shares of its common stock (including 2,000,000 shares of common stock issued in connection with the exercise in full by the underwriters of their over-allotment option) at a public offering price of $1.50 per share, for aggregate net proceeds of approximately $21.3 million . The Company intends to use the net proceeds of the offering of the shares for general corporate purposes, which may include research and development costs, sales and marketing costs, clinical studies, manufacturing development, the acquisition or licensing of other businesses or technologies, repayment and refinancing of debt, including the Company's secured term loan facility, working capital and capital expenditures.

Summary of Significant Accoun26

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of presentation and use of estimates	Basis of presentation and use of estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the consolidated financial statements, and the reported amounts of revenue and expenses during the reporting periods. The most significant estimates used in these consolidated financial statements include revenue recognition, accounts receivable valuation, inventory reserves, goodwill valuation, intangible valuation, purchase accounting, impairment assessments, equity instruments, stock compensation, income tax reserves and related allowances, and the lives of property and equipment. Actual results may differ from those estimates.
Concentrations of credit risk and other risks and uncertainties	Concentrations of credit risk and other risks and uncertainties Financial instruments that subject the Company to credit risk primarily consist of cash, cash equivalents and accounts receivable. The Company maintains the majority of its cash with accredited financial institutions. The Company and its contract manufacturers rely on sole source suppliers and service providers for certain components. There can be no assurance that a shortage or stoppage of shipments of the materials or components that the Company purchases will not result in a delay in production or adversely affect the Company’s business. On an on-going basis, the Company validates alternate suppliers relative to certain key components as needed. For the years ended December 31, 2017 , 2016 and 2015 , no customer represented greater than 10% of revenue. There were no customers that represented greater than 10% of total gross receivable balance at December 31, 2017 and 2016 .
Principles of consolidation	Principles of consolidation The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries including ImaTx, Inc. ("ImaTx"), ConforMIS Europe GmbH, ConforMIS UK Limited and ConforMIS Hong Kong Limited. All material intercompany balances and transactions have been eliminated in consolidation.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investment instruments with original maturities of 90 days or less when purchased, to be cash equivalents. The Company’s cash equivalents consist of demand deposits, money market accounts and repurchase agreements on deposit with certain financial institutions, in addition to cash deposits in excess of federally insured limits. Demand deposits are carried at cost which approximates their fair value. Money market accounts are carried at fair value based upon level 1 inputs. Repurchase agreements are valued using level 2 inputs. See “Note C — Fair Value Measurements” below. The associated risk of concentration is mitigated by banking with credit worthy financial institutions.
Investment securities	Investment securities The Company classifies its investment securities as available-for-sale. Those investments with maturities less than 12 months at the date of purchase are considered short-term investments. Those investments with maturities greater than 12 months at the date of purchase are considered long-term investments. The Company’s investment securities classified as available-for-sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses, deemed temporary in nature, are reported as a separate component of accumulated other comprehensive income (loss). A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums (discounts) are amortized (accreted) over the life of the related security using the constant yield method. Dividend and interest income are recognized when earned and reported in other income. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of securities sold.
Fair value of financial instruments	Fair value of financial instruments Certain of the Company’s financial instruments, including cash and cash equivalents (excluding money market funds), accounts receivable, accounts payable, accrued expenses and other liabilities are carried at cost, which approximates their fair value because of the short-term maturity. Based on borrowing rates currently available to the Company for loans with similar terms, the carrying value of the Company’s long-term debt approximates its fair value.
Accounts receivable and allowance for doubtful accounts	Accounts receivable and allowance for doubtful accounts Accounts receivable consist of billed and unbilled amounts due from medical facilities. Upon completion of a procedure, revenue is recognized and an unbilled receivable is recorded. Upon receipt of a purchase order number from a medical facility a billed receivable is recorded and the unbilled receivable is reversed. As a result, the unbilled receivable balance fluctuates based on the timing of the Company's receipt of purchase order numbers from the medical facilities. In estimating whether accounts receivable can be collected, the Company performs evaluations of customers and continuously monitors collections and payments and estimates an allowance for doubtful accounts based on the aging of the underlying invoices, collections experience to date and any specific collection issues that have been identified. The allowance for doubtful accounts is recorded in the period in which revenue is recorded or when collection risk is identified.
Inventories	Inventories Inventories consist of raw materials, work-in-process components and finished goods. Inventories are stated at the lower of cost, determined using the first-in first-out method, or net realizable value. The Company regularly reviews its inventory quantities on hand and related cost and records a provision for any excess or obsolete inventory based on its estimated forecast of product demand and existing product configurations. The Company also reviews its inventory value to determine if it reflects the lower of cost or market based on net realizable value. Appropriate consideration is given to inventory items sold at negative gross margin, purchase commitments and other factors in evaluating net realizable value.
Property and equipment	Property and equipment Property and equipment is stated at cost less accumulated depreciation and is depreciated using the straight-line method over the estimated useful lives of the respective assets. Leasehold improvements are amortized over their useful life or the life of the lease, whichever is shorter. Assets capitalized under capital leases are amortized in accordance with the respective class of assets and the amortization is included with depreciation expense. Maintenance and repair costs are expensed as incurred.
Business combinations and purchase accounting	Business combinations and purchase accounting The Company includes the results of operations of the businesses that it acquires as of the applicable acquisition date. The purchase price of the acquisition is allocated to the assets acquired and liabilities assumed based on their estimated fair values. The excess of the purchase price over the fair values of these identifiable assets and liabilities is recorded as goodwill. Acquisition-related expenses are recognized separately from the business combination and are expensed as incurred.
Intangibles and other long-lived assets	Intangibles and other long-lived assets Intangible assets consist of developed technology acquired as part of the ImaTx spin-out transaction in 2004 and a favorable lease asset from the Broad Peak Manufacturing, LLC ("BPM") acquisition in August 2017. Intangible assets are carried at cost less accumulated amortization. The Company tests impairment of long-lived assets when events or changes in circumstances indicate that the assets might be impaired. For assets with determinable useful lives, amortization is computed using the straight-line method over the estimated economic lives of the respective intangible assets. Furthermore, periodically the Company assesses whether long-lived assets, including intangible assets, should be tested for recoverability whenever events or circumstances indicate that their carrying value may not be recoverable. The amount of impairment, if any, is measured based on fair value, which is determined using estimated undiscounted cash flows to be generated from such assets or group of assets. If the cash flow estimates or the significant operating assumptions upon which they are based change in the future, the Company may be required to record impairment charges. In 2017, the Company recognized $1.1 million in impairment charges in general and administrative expense of which $0.8 million related to the discontinuance of a software capital project and $0.3 million related to intellectual property rights licensed as part of the ImaTx spin-out transaction in 2004. In 2016, a $0.1 million impairment charge was recognized in connection with certain manufacturing equipment previously purchased that will be returned to the seller in exchange for credit toward a future purchase, which value is less than the book value of the equipment.
Goodwill	Goodwill Goodwill relates to amounts that arose in connection with the acquisition of ImaTx, Inc. in 2009 and the acquisition of BPM in August 2017. The Company tests goodwill at least annually for impairment, or more frequently when events or changes in circumstances indicate that the assets may be impaired. This impairment test is performed annually during the fourth quarter at the reporting unit level. Goodwill may be considered impaired if the carrying value of the reporting unit, including goodwill, exceeds the reporting unit’s fair value. The Company is comprised of one reporting unit. When testing goodwill for impairment, the Company first assesses the qualitative factors to determine whether it is more likely than not that the fair value of its reporting unit is less than its carrying amount. This qualitative analysis is used as a basis for determining whether it is necessary to perform the one-step goodwill impairment analysis. If the Company determines that it is more likely than not that its fair value is less than its carrying amount, then the one-step goodwill impairment test will be performed. If the one-step approach is performed, the Company will estimate fair value of the reporting unit using the market approach to compare the Company's market capitalization with the carrying amount of its net assets on the date of the test, since the Company has only one reporting unit. An impairment of goodwill is recognized when the carrying amount exceeds the fair value. During the Company's 2017 impairment test, the Company's qualitative analysis indicated that a step one analysis is required to determine the fair value of the reporting unit. The Company used the market approach noting the reporting unit's fair value was substantially in excess of its carrying value. During the years ended December 31, 2016 and 2015 , there were no triggering events which would require goodwill impairment assessment.
Revenue recognition	Revenue recognition Product The Company generates revenue from the sale of customized implants and instruments to medical facilities through the use of a combination of direct sales personnel, independent sales representatives and distributors in the United States, Germany, the United Kingdom, Austria, Ireland, Switzerland, Singapore, Hong Kong, Malaysia and Monaco . Revenue was recognized when all of the following criteria are met: • persuasive evidence of an arrangement exists; • the sales price is fixed or determinable; • collection of the relevant receivable is probable at the time of sale; and • delivery has occurred or services have been rendered. The Company recognizes revenue upon completion of the procedure, which represents satisfaction of the required revenue recognition criteria. Once the revenue recognition criteria have been satisfied the Company does not offer rights of return or price protection and there are no post-delivery obligations. Royalty The Company accounted for its agreements with Wright Medical and MicroPort under ASC 605-25, Multiple-Element Arrangements and Staff Accounting Bulletin No. 104, Revenue Recognition (ASC 605). In accordance with ASC 605, the Company was required to identify and account for each of the separate units of accounting. The Company identified the relative selling price for each and then allocated the total consideration based on their relative values. Additionally, the Company recognized an initial $5.1 million in aggregate as deferred royalty revenue, to be recognized as royalty revenue ratably through 2031. The on-going royalty from MicroPort was recognized as royalty revenue upon receipt of payment.
Shipping and handling costs	Shipping and handling costs Amounts invoiced to customers for shipping and handling are classified as revenue. Shipping and handling costs incurred are included in general and administrative expense.
Taxes collected from customers and remitted to government authorities	Taxes collected from customers and remitted to government authorities The Company’s policy is to present taxes collected from customers and remitted to government authorities on a net basis and not to include tax amounts in revenue.
Research and development expense	Research and development expense The Company’s research and development costs consist of engineering, product development, quality assurance, clinical and regulatory expense. These costs primarily relate to employee compensation, including salary, benefits and stock-based compensation. The Company also incurs costs related to consulting fees, materials and supplies, and marketing studies, including data management and associated travel expense. Research and development costs are expensed as incurred.
Advertising expense	Advertising expense Advertising costs are expensed as incurred, which are included in sales and marketing.
Segment reporting	Segment reporting Operating segments are defined as components of an enterprise about which separate financial information is available and is evaluated on a regular basis by the chief operating decision-maker, or decision-making group, in deciding how to allocate resources to an individual segment and in assessing performance of the segment. The Company’s chief operating decision-maker is its chief executive officer. The Company’s chief executive officer reviews financial information presented on an aggregate basis for purposes of allocating resources and evaluating financial performance. The Company has one business segment and there are no segment managers who are held accountable for operations, operating results and plans for products or components below the aggregate Company level. Accordingly, in light of the Company’s current product offerings, management has determined that the primary form of internal reporting is aligned with the offering of the ConforMIS customized joint replacement products and that the Company operates as one segment. See “Note O-Segment and Geographic Data”.
Comprehensive loss	Comprehensive loss At December 31, 2017 and 2016 , accumulated other comprehensive loss consists of foreign currency translation adjustments and changes in unrealized gain and loss of available-for-sale securities, net of tax.
Foreign currency translation and transactions	Foreign currency translation and transactions The assets and liabilities of the Company’s foreign operations are translated into U.S. dollars at current exchange rates at the balance sheet date, and income and expense items are translated at average rates of exchange prevailing during the year. Net translation gains and losses are recorded in Accumulated other comprehensive (loss) income. Gains and losses realized from transactions denominated in foreign currencies, including intercompany balances not of a long-term investment nature, are included in the consolidated statements of operations.
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 consolidated financial statement carrying amounts of existing assets and liabilities and their respective tax bases, operating losses and tax credit carry forwards. 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 effect on deferred tax assets and liabilities of a change in tax rates is recognized as income in the period that includes the enactment date. In evaluating the need for a valuation allowance, the Company considers all reasonably available positive and negative evidence, including recent earnings, expectations of future taxable income and the character of that income. In estimating future taxable income, the Company relies upon assumptions and estimates of future activity including the reversal of temporary differences. Presently, the Company believes that a full valuation allowance is required to reduce deferred tax assets to the amount expected to be realized. The tax benefit from an uncertain tax position is only recognized if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the consolidated financial statements from these positions are measured based on the largest benefit that has a greater than fifty percent likelihood of being realized upon ultimate resolution. The Company reviews its tax positions on an annual basis and more frequently as facts surrounding tax positions change. Based on these future events, the Company may recognize uncertain tax positions or reverse current uncertain tax positions, the impact of which would affect the consolidated financial statements.
Medical device excise tax	Medical device excise tax The Company has been subject to the Health Care and Education Reconciliation Act of 2010 (the “Act”), which imposes a tax equal to 2.3% on the sales price of any taxable medical device by a medical device manufacturer, producer or importer of such device. Under the Act, a taxable medical device is any device defined in Section 201(h) of the Federal Food, Drug, and Cosmetic Act, intended for humans, which includes an instrument, apparatus, implement, machine, contrivance, implant, in vitro reagent, or other similar or related article, including any component, part, or accessory, which meets certain requirements. The Consolidated Appropriations Act of 2016 includes a two-year moratorium on the medical device excise tax, which moratorium suspended taxes on the sale of a taxable medical device by the manufacturer, producer, or importer of the device during the period beginning on January 1, 2016 and ending on December 31, 2017. As such, the Company did not incur medical device excise tax expense for the years ended December 31, 2017 and 2016 . The Company incurred medical device excise tax expense of $0.8 million for the year ended December 31, 2015 . On January 22, 2018, legislation was passed that suspends the medical device excise tax for sales in 2018 and 2019. The tax is not scheduled to take effect again until sales on or after January 1, 2020. It is unclear at this time if the suspension will be further extended, and we are currently subject to the tax after December 31, 2019.
Stock-based compensation	Stock-based compensation The Company accounts for stock-based compensation in accordance with ASC 718, Stock Based Compensation. ASC 718 requires all stock-based payments to employees and consultants, including grants of stock options, to be recognized in the consolidated statements of operations based on their fair values. The Company uses the Black-Scholes option pricing model to determine the weighted-average fair value of options granted and recognizes the compensation expense of stock-based awards on a straight-line basis over the vesting period of the award. The determination of the fair value of stock-based payment awards utilizing the Black-Scholes option pricing model is affected by the stock price, exercise price, and a number of assumptions, including expected volatility of the stock, expected life of the option, risk-free interest rate and expected dividends on the stock. The Company evaluates the assumptions used to value the awards at each grant date and if factors change and different assumptions are utilized, stock-based compensation expense may differ significantly from what has been recorded in the past. 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. Prior to the Company’s IPO in July 2015, the exercise price of stock option awards was determined by the Company's board of directors based on a number of factors in determining the option price, including: (1) past sales of the Company’s convertible preferred stock, and the rights, preferences and privileges of the Company stock, (2) obtaining FDA 510(k) clearance, and (3) achievement of budgeted results. See “Note M——Stockholders’ Equity” for a summary of the stock option activity under the Company’s stock-based compensation plan.
Net loss per share	Net loss per share The Company calculates net loss per share in accordance with ASC 260, "Earnings per Share". Basic earnings per share (“EPS”) is calculated by dividing the net income or loss for the period by the weighted average number of common shares outstanding for the period, without consideration for common stock equivalents. Diluted EPS is computed by dividing the net income or loss for the period by the weighted average number of common shares outstanding for the period and the weighted average number of dilutive common stock equivalents outstanding for the period determined using the treasury stock method.
Recent accounting pronouncements	Recent accounting pronouncements In May 2017, the FASB issued ASU No. 2017-09, "Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting". This ASU provides clarification on when changes to the terms or conditions of a share-based payment award must be accounted for as a modification. The guidance will be effective in the first quarter of 2018, with early adoption permitted. The Company is does not believe that the adoption of ASU 2017-09 will have a material impact on its consolidated financial statements and expects to adopt this pronouncement commencing in the first quarter of 2018. In January 2017, the FASB issued ASU No. 2017-04, "Intangibles- Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment". This ASU removes the second step of the two-step test to determine goodwill impairment previously required. Entities will now apply a one-step quantitative test and record the amount of goodwill impairment as the excess of a reporting unit's carrying amount over its fair value, not to exceed the total amount of goodwill allocated to the reporting unit. The new guidance does not amend the optional qualitative assessment of goodwill impairment. The guidance will be effective in the first quarter of 2020, with early adoption permitted. The Company has elected to early adopt this new pronouncement in 2017 noting no material impact on its consolidated financial statements . In November 2016, the FASB issued ASU No. 2016-18, “Statement of Cash Flows (Topic 230) Restricted Cash a consensus of the FASB Emerging Issues Task Force”. The standard requires restricted cash and cash equivalents to be included with cash and cash equivalents on the statement of cash flows. The guidance will be effective in the first quarter of 2018, with early adoption permitted. The Company evaluated the impact of this pronouncement noting the Company's cash flow disclosure currently reflects ASU No. 2016-18 disclosure requirements. The Company expects to adopt this pronouncement commencing in the first quarter of 2018. In February 2016, the FASB issued ASU No. 2016-02, "Leases (Topic 842)." This ASU amends various aspects of existing guidance for leases and requires additional disclosures about leasing arrangements. It will require companies to recognize lease assets and lease liabilities by lessees for those leases classified as operating leases under GAAP. Topic 842 retains a distinction between finance leases and operating leases. The classification criteria for distinguishing between finance leases and operating leases are substantially similar to the classification criteria for distinguishing between capital leases and operating leases in the previous leases guidance. This ASU is effective for annual periods beginning after December 15, 2018, including interim periods within those fiscal years; earlier adoption is permitted. In the financial statements in which the ASU is first applied, leases shall be measured and recognized at the beginning of the earliest comparative period presented with an adjustment to equity. Practical expedients are available for election as a package and if applied consistently to all leases. The Company is currently evaluating the impact of this pronouncement on its consolidated financial statements and expects to adopt this pronouncement commencing in the first quarter of 2019. In May 2014, the FASB issued ASU No. 2014-9, “Revenue from Contracts with Customers (Topic 606)”. ASU 2014-9 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. The core principle of the revenue model is that an entity recognizes revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. In applying the revenue model to contracts within its scope, an entity identifies the contract(s) with a customer, identifies the performance obligations in the contract, determines the transaction price, allocates the transaction price to the performance obligations in the contract, and recognizes revenue when (or as) the entity satisfies a performance obligation. ASU 2014-09 applies to all contracts with customers that are within the scope of other topics in the FASB Accounting Standards Codification. ASU 2014-09 also requires significantly expanded disclosures about revenue recognition. Companies have the option of using either a full retrospective or a modified retrospective approach to adopt the guidance. In March 2016, the FASB issued ASU No 2016-08, "Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net)", which clarifies the implementation guidance on principal versus agent considerations. The guidance includes indicators to assist an entity in determining whether it controls a specified good or service before it is transferred to the customers. In April 2016, the FASB issued ASU 2016-10, "Identifying Performance Obligations and Licensing" ("ASU 2016-10"). This ASU clarifies two aspects of ASU 2014-09, "Revenue from Contracts with Customers (Topic 606): identifying performance obligations and the licensing implementation guidance". Disclosure requirements are expanded regarding an entity’s assumptions, models and methods of estimations of the allowance. In November 2017, the FASB issued ASU 2017-14, "Income Statement - Reporting Comprehensive Income (Topic 220), Revenue Recognition (Topic 605), and Revenue from Contracts with Customers (Topic 606)", which amends the ASU 2016-10 to align SEC guidance with the new guidance in ASC 606. The Company has completed its assessment process to evaluate the impact, and will adopt this pronouncement and related disclosures commencing in the first quarter of 2018. The Company plans to adopt this standard using the modified retrospective approach as of January 1, 2018, which will apply to all contracts not completed as of January 1, 2018. The adoption of ASC 606 will require additional disclosure around the Company’s revenue recognition in its financial statements. The Company has established a cross-functional coordinated implementation team and engaged a third party consultant to assist with the assessment and implementation. The Company has completed the scoping and planning phase of the project, identified and reviewed customer contracts for each of its revenue streams, including royalty revenue, and has evaluated the results of those reviews relative to the new standard. Based on the results of the procedures, the Company does not expect a material impact on its consolidated financial statements with regards to revenue recognized from the sale of its product to customers. The Company expects that, based on its assessment, certain royalty revenue associated with the 2015 license agreements with Wright Medical and MicroPort will be accelerated upon the adoption of this new standard which will require an adjustment to retained earnings for approximately $4 million . The Company has also completed its evaluation of changes to its processes and internal controls, as necessary, to meet the requirements. Change in accounting policy regarding share-based compensation Effective January 1, 2017, the Company elected to change its accounting policy to recognize forfeitures as they occur in accordance with ASU 2016-09, "Compensation - Stock Compensation". Historically, the Company recognized share-based compensation net of estimated forfeitures over the vesting period of the respective grant. The new forfeiture policy election was adopted using a modified retrospective approach with a cumulative effect adjustment of $0.3 million to accumulated deficit and an offset to APIC as of January 1, 2017. ASU No. 2016-09, "Compensation - Stock Compensation", was issued and adopted in January 2017. ASU 2016-09 eliminates APIC pools and requires excess tax benefits and tax deficiencies to be recorded in the income statement when the awards vest or are settled. In addition, modified retrospective adoption of ASU 2016-09 eliminates the requirement that excess tax benefits be realized (i.e., through a reduction in income taxes payable) before we can recognize them and therefore, we have accounted for a cumulative-effect adjustment of $7.7 million for the year-ended December 31, 2017 to record excess tax benefits. Since the Company has a full valuation allowance on all deferred taxes, this has no impact on retained earnings or the tax position of the Company.

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of accumulated other comprehensive income (loss)	The following table summarizes accumulated beginning and ending balances for each item in Accumulated other comprehensive income (loss) (in thousands): Foreign currency translation adjustments Change in unrealized gain (loss) on available-for-sale securities, net of tax Accumulated other comprehensive income (loss) Balance December 31, 2016 $ 506 $ (7 ) $ 499 Change in period (3,709 ) (26 ) (3,735 ) Balance December 31, 2017 $ (3,203 ) $ (33 ) $ (3,236 )
Schedule of computation of basic and diluted earnings per share attributable to stockholders	The following table sets forth the computation of basic and diluted earnings per share attributable to stockholders (in thousands, except share and per share data): Years Ended December 31, (in thousands, except share and per share data) 2017 2016 2015 Numerator: Numerator for basic and diluted loss per share: Net loss $ (53,580 ) $ (57,588 ) $ (57,246 ) Denominator: Denominator for basic loss per share: Weighted average shares 43,343,459 41,521,629 21,993,066 Basic loss per share attributable to ConforMIS, Inc. stockholders $ (1.24 ) $ (1.39 ) $ (2.60 ) Diluted loss per share attributable to ConforMIS, Inc. stockholders $ (1.24 ) $ (1.39 ) $ (2.60 )
Schedule of potential shares of common stock equivalents that are antidilutive and not included in the calculation of diluted net loss per share	The following table sets forth potential shares of common stock equivalents that are not included in the calculation of diluted net loss per share because to do so would be anti-dilutive as of the end of each period presented: Years Ended December 31, 2017 2016 2015 Series A Preferred — — 873,591 Series B Preferred — — 1,144,885 Series C Preferred — — 1,256,752 Series D Preferred — — 3,410,570 Series E-1 Preferred — — 3,748,578 Series E-2 Preferred — — 2,628,037 Common stock warrants — 34,709 303,931 Stock options 365,105 1,959,030 3,566,421 Total 365,105 1,993,739 16,932,765

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table summarizes, by major security type, the Company's assets that are measured at fair value on a recurring basis and are categorized using the fair value hierarchy and where they are classified on the Consolidated Balance Sheets (in thousands): December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents Short-term (1) investments Cash $ 9,849 $ — $ — $ 9,849 $ 9,849 $ — Level 1 securities: Money market funds 3,499 — — 3,499 3,499 — U.S. treasury bonds 9,243 — (4 ) 9,239 — 9,239 Level 2 securities: Corporate bonds 4,935 — (6 ) 4,929 — 4,929 Agency bond 12,734 — (22 ) 12,712 — 12,712 Repurchase agreement 5,000 — — 5,000 5,000 — Total $ 45,260 $ — $ (32 ) $ 45,228 $ 18,348 $ 26,880 December 31, 2016 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value Cash and cash equivalents Short-term (1) investments Cash $ 8,504 $ — $ — $ 8,504 $ 8,504 $ — Level 1 securities: Money market funds 28,753 — — 28,753 28,753 — Level 2 securities: Corporate bonds 6,701 — (4 ) 6,697 — 6,697 Agency bonds 21,548 — (3 ) 21,545 — 21,545 Total $ 65,506 $ — $ (7 ) $ 65,499 $ 37,257 $ 28,242 (1) Contractual maturity due within one year.

Accounts Receivable (Tables)

Accounts Receivable (Tables)	12 Months Ended
	Dec. 31, 2017
Accounts Receivable, Net, Current [Abstract]
Schedule of accounts receivable	Accounts receivable consisted of the following (in thousands): December 31, December 31, Total receivables $ 13,835 $ 15,356 Allowance for doubtful accounts and returns (635 ) (681 ) Accounts receivable, net $ 13,200 $ 14,675
Allowance for doubtful accounts receivable	Summary of allowance for doubtful accounts and returns activity was as follows (in thousands): December 31, 2017 December 31, 2016 Beginning balance $ (681 ) $ (554 ) Provision for bad debts on trade receivables 15 (188 ) Other allowances (61 ) 20 Accounts receivable write offs 92 41 Ending balance $ (635 ) $ (681 )

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2017
Inventory Disclosure [Abstract]
Schedule of inventories	Inventories consisted of the following (in thousands): December 31, December 31, Raw Material $ 2,905 $ 3,331 Work in process 1,718 2,530 Finished goods 4,561 5,859 Total Inventories $ 9,184 $ 11,720

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): Estimated Useful Life (Years) December 31, December 31, Equipment 5-7 $ 19,331 $ 16,651 Furniture and fixtures 5-7 955 414 Computer and software 3 7,877 7,027 Leasehold improvements 2-8 1,830 1,294 Total property and equipment 29,993 25,386 Accumulated depreciation (13,479 ) (10,302 ) Property and equipment, net $ 16,514 $ 15,084

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Components of intangible assets	The components of intangible assets consisted of the following (in thousands): Estimated Useful Life (Years) December 31, 2017 December 31, 2016 Developed technology 10 $ 979 $ 979 Accumulated amortization (783 ) (681 ) Developed technology, net 196 298 License agreements 10 — 1,508 Accumulated amortization — (1,060 ) License technology, net — 448 Acquired favorable lease 5 15 — Accumulated amortization (1 ) — Acquired favorable lease, net 14 — Intangible assets, net $ 210 $ 746
Schedule of estimated future aggregated amortization expense	The estimated future aggregated amortization expense for intangible assets owned as of December 31, 2017 consisted of the following (in thousands): Amortization expense 2018 $ 101 2019 101 2020 3 2021 3 2022 2 $ 210

Accrued Expenses (Tables)

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2017
Accrued Liabilities and Other Liabilities [Abstract]
Schedule of accrued expenses	Accrued expenses consisted of the following (in thousands): December 31, 2017 December 31, 2016 Accrued employee compensation $ 2,989 $ 4,037 Deferred rent 115 101 Accrued legal expense 1,231 710 Accrued consulting expense 115 104 Accrued vendor charges 912 1,396 Accrued revenue share expense 968 992 Accrued clinical trial expense 196 256 Accrued other 1,194 896 $ 7,720 $ 8,492

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum rental payments under the entity's non-cancellable operating leases	The future minimum rental payments under the Company’s non-cancellable operating leases for real estate as of December 31, 2017 were as follows (in thousands): Year Minimum lease Payments 2018 $ 1,521 2019 1,558 2020 1,595 2021 1,633 2022 1,397 2023-2025 2,939 $ 10,643
Contractual obligation, fiscal year maturity schedule	The following table summarizes the Company's contractual obligations as of the year ended December 31, 2017 (in thousands): Payment Due by Period Total Less than 1 year Years 1 to 3 Years 3 to 5 After 5 years Contractual Obligations (1)(2) $ 1,435 $ 378 $ 756 $ 301 $ — (1) Represents amounts payable under our product royalty agreement, operating leases for office equipment, and a software development collaboration project with a remaining term in excess of one year. (2) This table does not include: (a) revenue share obligations to past and present members of our scientific advisory board and one of our directors, as the amounts of such payments are not known with certainty; and (b) contracts that are entered into in the ordinary course of business that are not material in the aggregate in any period presented above. See "—Revenue share agreements" for a description of our revenue share arrangements.

Debt and Notes Payable (Tables)

Debt and Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of long term debt	Long-term debt consisted of the following (in thousands): December 31, 2017 December 31, 2016 Oxford Finance, LLC, Term A Loan $ 15,000 $ — Oxford Finance, LLC, Term B Loan 15,000 30,000 — Less unamortized debt issuance costs (333 ) — Long-term debt, less debt issuance costs $ 29,667 $ —
Schedule of maturities of long-term debt	Principal payments due as of December 31, 2017 consisted of the following (in thousands): Principal 2018 $ — 2019 — 2020 13,750 2021 15,000 2022 1,250 Total $ 30,000

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2017
Schedule of common stock activity	Summary of common stock activity was as follows: Shares Outstanding December 31, 2015 41,110,127 Issuance of common stock - option & warrant exercises 1,485,401 Issuance of restricted common stock 804,019 Outstanding December 31, 2016 43,399,547 Issuance of common stock - option 535,734 Issuance of restricted common stock 1,195,196 Issuance of common stock - ATM offering 228,946 Issuance of common stock - BPM acquisition 169,096 Outstanding December 31, 2017 45,528,519
Schedule of activity under all stock option plans	Activity under all stock option plans was as follows: Number of Options Weighted Average Exercise Price per Share Aggregate Intrinsic Value (In Thousands) Outstanding December 31, 2014 5,355,567 $ 4.87 Granted 403,086 12.20 Exercised (383,458 ) 2.10 $ 5,691 Expired (30,876 ) 5.97 Cancelled/Forfeited (95,990 ) 7.42 Outstanding December 31, 2015 5,248,329 $ 5.56 $ 61,741 Granted 179,178 8.78 Exercised (1,467,692 ) 2.78 8,219 Expired (81,251 ) 9.70 Cancelled/Forfeited (88,524 ) 9.93 Outstanding December 31, 2016 3,790,040 $ 6.60 $ 8,547 Granted 963,350 4.95 Exercised (535,734 ) 3.94 1,688 Expired (466,210 ) 7.17 Cancelled/Forfeited (123,451 ) 6.54 Outstanding December 31, 2017 3,627,995 $ 6.48 $ 96 Total vested and exercisable 2,696,151 $ 6.66 $ 96
Schedule of restricted common stock award activity	Restricted common stock award activity under the plan was as follows: Number of Shares Weighted Average Fair Value Unvested December 31, 2014 — $ — Granted 174,530 22.31 Unvested December 31, 2015 174,530 22.31 Granted 873,589 8.61 Vested (66,839 ) 17.72 Forfeited (69,570 ) 11.83 Unvested December 31, 2016 911,710 $ 10.32 Granted 1,421,364 4.20 Vested (767,785 ) 7.11 Forfeited (226,168 ) 7.36 Unvested December 31, 2017 1,339,121 $ 6.06
Assumptions used to estimate the fair value of options at date of grant	The fair value of options at date of grant was estimated using the Black-Scholes option pricing model, based on the following assumptions: Years Ended December 31, 2017 2016 2015 Risk-free interest rate 2.10% - 2.30% 1.98% 1.37% - 1.77% Expected term (in years) 6.02 - 6.25 6.25 5.47 - 6.45 Dividend yield —% —% —% Expected volatility 51.00% - 53.00% 51.00% 49.00% - 50.00%
Summary of stock-based compensation expense	The following is a summary of stock-based compensation expense (in thousands): Years Ended December 31, 2017 2016 2015 Cost of revenue $ 441 $ 333 $ 239 Sales and marketing 919 1,197 730 Research and development 1,920 1,466 784 General and administrative 2,768 2,328 1,854 $ 6,048 $ 5,324 $ 3,607
Common stock warrants
Summary of stock warrant activity	Summary of common stock warrant activity was as follows: Number of Warrants Weighted Average Exercise Price Per Share Number of Warrants Exercisable Weighted Average Price Per Share Weighted Average Contractual Life Outstanding December 31, 2015 751,779 $ 10.30 751,779 $ 10.30 1.33 Exercised (166,665 ) 9.00 (166,665 ) 9.00 — Cancelled/expired (413,331 ) — (413,331 ) — — Outstanding December 31, 2016 171,783 $ 7.47 171,783 $ 7.47 1.62 Cancelled/expired (142,857 ) 7.00 (142,857 ) 7.00 — Outstanding December 31, 2017 28,926 $ 9.80 28,926 $ 9.80 5.66

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of income before income tax, domestic and foreign	For financial reporting purposes, income (loss) before income taxes for the years ended December 31, 2017 , 2016 and 2015 include the following components (in thousands): Years ended December 31, 2017 2016 2015 Loss before income taxes: U.S. $ (53,274 ) $ (51,576 ) $ (50,155 ) Non‑U.S. (144 ) (5,949 ) (7,050 ) $ (53,418 ) $ (57,525 ) $ (57,205 )
Schedule of components of income tax expense (benefit)	Significant components of the provision for income taxes for the years ended December 31, 2017 , 2016 and 2015 were as follows (in thousands): Years ended December 31, 2017 2016 2015 Current: Federal $ — $ — $ — State — — — Foreign 125 63 41 125 63 41 Deferred: Federal 31 — — State 6 — — Foreign — — — 37 — Total $ 162 $ 63 $ 41
Schedule of effective income tax rate reconciliation	A reconciliation of the income tax expense (benefit) at the statutory federal income tax rate as reflected in the financial statements was as follows: Years ended December 31, 2017 2016 2015 Tax at U.S. statutory rate (34.00 )% (34.00 )% (34.00 )% State taxes, net of federal benefits (3.12 ) (2.70 ) (2.27 ) Permanent items 1.96 0.42 1.52 Tax credit (1.35 ) (1.06 ) (0.85 ) Change in valuation allowance (54.85 ) 33.95 31.07 Foreign rate differential (0.17 ) 1.04 1.68 Rate change 90.78 (0.06 ) 0.01 Uncertain tax positions 0.41 2.06 2.21 Other 0.64 0.46 0.70 0.30 % 0.11 % 0.07 %
Schedule of deferred tax assets and liabilities	Significant components of the Company’s deferred tax assets (liabilities) consisted of the following (in thousands): Years ended December 31, 2017 2016 Deferred tax assets: Federal and state net operating loss carryforwards $ 90,437 $ 115,719 Foreign net operating loss carryforwards 2,561 2,561 Accrued expenses 157 280 Credits 6,055 5,091 Deferred revenue 1,068 1,709 Stock compensation expense 1,805 2,946 Other 2,111 2,757 Total deferred tax assets 104,194 131,063 Valuation allowance (103,430 ) (130,005 ) Net deferred tax assets 764 1,058 Deferred tax liabilities: Fixed assets (664 ) (841 ) Intangibles (134 ) (217 ) Other (3 ) — Net deferred tax liabilities (801 ) (1,058 ) Net deferred tax liabilities $ (37 ) $ —
Schedule of unrecognized tax benefits	Years ended December 31, 2017 2016 2015 Unrecognized tax benefits beginning of year $ 4,918 $ 3,730 $ 2,466 Gross change for current year positions 219 1,187 1,264 Unrecognized tax benefits end of the year $ 5,136 $ 4,918 $ 3,730

Segment and Geographic Data (Ta

Segment and Geographic Data (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of revenue by geographic information	Geographic information consisted of the following (in thousands): Years Ended December 31, 2017 2016 2015 Product Revenue United States $ 64,390 $ 62,366 $ 47,223 Germany 11,217 14,701 13,795 Rest of World 1,493 1,854 1,773 $ 77,100 $ 78,921 $ 62,791
Schedule of property, plant and equipment by geographic information	December 31, 2017 2016 Property and equipment, net United States $ 16,424 $ 14,971 Rest of World 90 113 $ 16,514 $ 15,084

Selected Quarterly Financial 39

Selected Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Three Months Ended December 31, 2016 September 30, 2016 June 30, 2016 March 31, 2016 Total revenue $ 21,673 $ 18,643 $ 19,333 $ 20,250 Gross profit 8,045 5,998 6,001 6,663 Net loss (15,740 ) (12,762 ) (14,052 ) (15,034 ) Net loss per share - basic and diluted $ (0.37 ) $ (0.31 ) $ (0.34 ) $ (0.37 )

Organization and Basis of Pre40

Organization and Basis of Presentation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Accumulated deficit	$ 436,821	$ 382,930
Cash and cash equivalents and investments	45,200
Restricted cash	$ 500	$ 300

Organization and Basis of Pre41

Organization and Basis of Presentation (Details 2)	Jan. 06, 2017USD ($)loan	Jan. 31, 2017USD ($)	Sep. 30, 2017USD ($)
Liquidity and operations
Amount of equity able to raise		$ 200,000,000
2017 Secured Loan Agreement | Term loan
Liquidity and operations
Number of loans | loan	3
Maximum amount committed by the lenders under the loan and security agreement	$ 50,000,000
2017 Secured Loan Agreement | Term loan | Oxford Term Loan
Liquidity and operations
Maximum amount committed by the lenders under the loan and security agreement	15,000,000
Amount drawn down	15,000,000
2017 Secured Loan Agreement | Term loan | Oxford Finance, LLC, Term B Loan
Liquidity and operations
Maximum amount committed by the lenders under the loan and security agreement		$ 15,000,000	$ 15,000,000
2017 Secured Loan Agreement | Term loan | Oxford Term Loan C
Liquidity and operations
Maximum amount committed by the lenders under the loan and security agreement	$ 20,000,000		$ 20,000,000

Organization and Basis of Pre42

Organization and Basis of Presentation (Details 3) - USD ($)	Jan. 29, 2018	May 10, 2017	Jan. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Amount of equity able to raise			$ 200,000,000
Maximum offering price		$ 50,000,000
Issuance of common stock (in shares)				228,946
Net proceeds from issuance of common stock				$ 1,023,000	$ 0	$ 139,766,000
Equity Distribution Agreement
Class of Stock [Line Items]
Issuance of common stock (in shares)				228,946
Net proceeds from issuance of common stock				$ 1,000,000
Subsequent Event
Class of Stock [Line Items]
Sale of stock (in dollars per share)	$ 1.50
Subsequent Event | Shelf Registration Statement
Class of Stock [Line Items]
Number of shares issued (in shares)	15,333,333
Sale of stock net proceeds	$ 21,300,000
Subsequent Event | Over-Allotment Option
Class of Stock [Line Items]
Number of shares issued (in shares)	2,000,000

Summary of Significant Accoun43

Summary of Significant Accounting Policies (Concentration RIsk) (Details) - customer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Credit Concentration Risk
Concentration Risk [Line Items]
Concentration risk, number of customers	0	0	0
Customer Concentration Risk
Concentration Risk [Line Items]
Concentration risk, number of customers	0	0	0

Summary of Significant Accoun44

Summary of Significant Accounting Policies (Cash and Cash Equivalents and Asset Impairment Charges) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Accounting Policies [Abstract]
Cash held in foreign bank accounts	$ 2,200	$ 1,600
Restricted cash	500	300
Asset Impairment Charges [Abstract]
Impairment of long term assets	$ 1,113	$ 123	$ 0
Number of reporting units for goodwill testing | segment	1

Summary of Significant Accoun45

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Inventories) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory [Line Items]
Cost of revenue	$ 49,301	$ 53,192	$ 45,102
Improper Classification of Cost of Revenue [Member]
Inventory [Line Items]
Cost of revenue	$ 2,600
Restatement Adjustment [Member] | Improper Classification of Cost of Revenue [Member]
Inventory [Line Items]
Cost of revenue		$ 3,500	$ 2,700

Summary of Significant Accoun46

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets
Asset impairment charges	$ 1,100
Impairment of long term assets	1,113	$ 123	$ 0
License agreements
Intangible assets
Asset impairment charges	300
Impairment of Intangible Assets, Finite-lived	300
Software and Software Development Costs
Intangible assets
Asset impairment charges	$ 800

Summary of Significant Accoun47

Summary of Significant Accounting Policies (Revenue Recognition) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Apr. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Shipping and handling costs
Shipping and handling expenses		$ 1.4	$ 1.6	$ 2.7
Worldwide license agreement | Wright Medical and MicroPort
Revenue recognition
Deferred royalty revenue	$ 5.1

Summary of Significant Accoun48

Summary of Significant Accounting Policies (Expenses and Net Loss Per Share) (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2017USD ($)segment$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Advertising expense
Advertising expense									$ 400,000	$ 300,000	$ 300,000
Medical device excise tax
Excise tax on sales (as a percent)									2.30%
Medical device excise tax expense									$ 0		800,000
Segment reporting
Number of operating segments | segment									1
Numerator for basic and diluted loss per share:
Net loss	$ (11,858,000)	$ (12,472,000)	$ (12,090,000)	$ (17,160,000)	$ (15,740,000)	$ (12,762,000)	$ (14,052,000)	$ (15,034,000)	$ (53,580,000)	$ (57,588,000)	$ (57,246,000)
Denominator for basic loss per share:
Weighted average shares | shares									43,343,459	41,521,629	21,993,066
Basic loss per share attributable to ConforMIS, Inc. stockholders (in dollars per share) | $ / shares									$ (1.24)	$ (1.39)	$ (2.60)
Diluted loss per share attributable to ConforMIS, Inc. stockholders (in dollars per share) | $ / shares									$ (1.24)	$ (1.39)	$ (2.60)

Summary of Significant Accoun49

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Schedule of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 94,055	$ 141,212	$ 49,827
Change in period	(3,735)	1,020	(24)
Ending balance	46,513	94,055	141,212
Foreign currency translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	506
Change in period	(3,709)
Ending balance	(3,203)	506
Change in unrealized gain (loss) on available-for-sale securities, net of tax
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(7)
Change in period	(26)
Ending balance	(33)	(7)
Accumulated other comprehensive income (loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	499	(521)	(497)
Change in period	(3,735)	1,020	(24)
Ending balance	$ (3,236)	$ 499	$ (521)

Summary of Significant Accoun50

Summary of Significant Accounting Policies (Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share) (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	365,105	1,993,739	16,932,765
Preferred stock | Series A convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	873,591
Preferred stock | Series B convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	1,144,885
Preferred stock | Series C convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	1,256,752
Preferred stock | Series D convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	3,410,570
Preferred stock | Series E-1 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	3,748,578
Preferred stock | Series E-2 convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	0	2,628,037
Warrants | Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	0	34,709	303,931
Equity options
Antidilutive Securities Excluded from Computation of Earnings Per Share
Anti-dilutive shares not included in the calculation of diluted net loss per share	365,105	1,959,030	3,566,421

Summary of Significant Accoun51

Summary of Significant Accounting Policies (Adoption of New Accounting Standards) (Details) - USD ($)	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit		$ (436,821,000)	$ (382,930,000)
Cumulative effect of new accounting principle in period of adoption			0
Accounting Standards Update 2016-09, Excess Tax Benefit Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		(7,700,000)
Additional Paid-in Capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			(311,000)
Additional Paid-in Capital | Accounting Standards Update 2016-09, Forfeiture Rate Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			(300,000)
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			311,000
Retained Earnings | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			0
Retained Earnings | Accounting Standards Update 2016-09, Forfeiture Rate Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption			300,000
Subsequent Event | Retained Earnings | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit	$ 4,000,000
Deferred Tax Asset | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 7,700,000	$ 7,700,000

Summary of Significant Accoun52

Summary of Significant Accounting Policies (Reclassification) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	$ 49,301	$ 53,192	$ 45,102
Selling and Marketing Expense	(38,788)	(41,086)	(37,558)
Improper Classification of Cost of Revenue [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue	$ 2,600
Restatement Adjustment [Member] | Improper Classification of Cost of Revenue [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of revenue		3,500	2,700
Selling and Marketing Expense		$ 2,700	$ 1,700

Fair Value Measurements (Schedu

Fair Value Measurements (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash	$ 9,849	$ 8,504
Cash and cash equivalents	9,849	8,504
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Losses	(32)	(7)
Total, Amortized Costs	45,260	65,506
Total, Fair Value	45,228	65,499
Cash and cash equivalents
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	9,849	8,504
Total, Fair Value	18,348	37,257
Short-term investments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Total, Fair Value	26,880	28,242
Money market funds | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	3,499	28,753
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	3,499	28,753
Money market funds | Cash and cash equivalents | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	3,499	28,753
Money market funds | Short-term investments | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
U.S. treasury bonds | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	9,243
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0
Gross Unrealized Losses	(4)
Estimated Fair Value	9,239
U.S. treasury bonds | Cash and cash equivalents | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0
U.S. treasury bonds | Short-term investments | Level 1 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	9,239
Corporate bonds | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	4,935	6,701
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Losses	(6)	(4)
Estimated Fair Value	4,929	6,697
Corporate bonds | Cash and cash equivalents | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Corporate bonds | Short-term investments | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	4,929	6,697
Agency bond | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	12,734	21,548
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Gross Unrealized Losses	(22)	(3)
Estimated Fair Value	12,712	21,545
Agency bond | Cash and cash equivalents | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	0	0
Agency bond | Short-term investments | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	12,712	$ 21,545
Repurchase agreement | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized Cost	5,000
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0
Gross Unrealized Losses	0
Estimated Fair Value	5,000
Repurchase agreement | Cash and cash equivalents | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	5,000
Repurchase agreement | Short-term investments | Level 2 securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated Fair Value	$ 0

Accounts Receivable (Details)

Accounts Receivable (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts Receivable, Net, Current [Abstract]
Total receivables	$ 13,835	$ 15,356
Allowance for doubtful accounts and returns	(635)	(681)
Accounts receivable, net	13,200	14,675
Unbilled receivable	1,400	2,500
Accounts receivable write offs	$ 92	$ 41	$ 88

Accounts Receivable (Details 2)

Accounts Receivable (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Allowance For Doubtful Accounts Receivable [Line Items]
Beginning balance	$ (681)	$ (554)
Provision for bad debts on trade receivables	15	(188)	$ (359)
Accounts receivable write offs	92	41	88
Ending balance	(635)	(681)	$ (554)
Trade Accounts Receivable
Allowance For Doubtful Accounts Receivable [Line Items]
Provision for bad debts on trade receivables	15	(188)
Other Receivable
Allowance For Doubtful Accounts Receivable [Line Items]
Other allowances	$ (61)	$ 20

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw Material	$ 2,905	$ 3,331
Work in process	1,718	2,530
Finished goods	4,561	5,859
Total Inventories	9,184	11,720
Inventories write-downs	$ 0	$ 200

Acquisition (Details)

Acquisition (Details) - USD ($)	Aug. 09, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Purchase price attributable to goodwill		$ 6,731,000	$ 753,000
Broad Peak Manufacturing, LLC
Business Acquisition [Line Items]
Purchase price	$ 6,400,000
Purchase price, cash	5,800,000
Purchase price, unregistered shares of common stock	600,000
Amount paid into escrow account	2,200,000
Potential additional consideration that could be earned if actual cost targets are exceeded	700,000
Estimated amount of consideration expected to be returned	0
Estimated amount of additional consideration expected to be earned (less than)	100,000
Purchase price attributable to property and equipment	400,000
Purchase price attributable to goodwill	6,000,000
Purchase price attributable to other net assets acquired (less than)	$ 100,000

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property and equipment
Total property and equipment	$ 29,993	$ 25,386
Accumulated depreciation	(13,479)	(10,302)
Property and equipment, net	16,514	15,084
Depreciation expense	3,400	2,900	$ 2,400
Asset impairment charges	1,100
Impairment of long term assets	1,113	123	$ 0
Equipment
Property and equipment
Total property and equipment	$ 19,331	16,651
Equipment | Minimum
Property and equipment
Estimated useful life	5 years
Equipment | Maximum
Property and equipment
Estimated useful life	7 years
Furniture and fixtures
Property and equipment
Total property and equipment	$ 955	414
Furniture and fixtures | Minimum
Property and equipment
Estimated useful life	5 years
Furniture and fixtures | Maximum
Property and equipment
Estimated useful life	7 years
Computer and software
Property and equipment
Estimated useful life	3 years
Total property and equipment	$ 7,877	7,027
Leasehold improvements
Property and equipment
Total property and equipment	$ 1,830	$ 1,294
Leasehold improvements | Minimum
Property and equipment
Estimated useful life	2 years
Leasehold improvements | Maximum
Property and equipment
Estimated useful life	8 years
Software and Software Development Costs
Property and equipment
Asset impairment charges	$ 800

Intangible Assets (Details)

Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Intangible assets
Asset impairment charges	$ 1,100
Intangible assets, net	$ 210	$ 746
Estimated useful life
Amortization expense	$ 200	200	$ 200
Weighted Average
Intangible assets
Estimated useful life	2 years 2 months 12 days
Developed technology
Intangible assets
Total intangible assets	$ 979	979
Accumulated amortization	(783)	(681)
Intangible assets, net	$ 196	298
Estimated useful life	10 years
License agreements
Intangible assets
Asset impairment charges	$ 300
Total intangible assets	0	1,508
Accumulated amortization	0	(1,060)
Intangible assets, net	$ 0	448
Estimated useful life	10 years
Acquired favorable lease
Intangible assets
Total intangible assets	$ 15	0
Accumulated amortization	(1)	0
Intangible assets, net	$ 14	$ 0
Estimated useful life	5 years

Intangible Assets (Details 2)

Intangible Assets (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Estimated future amortization expense for intangible assets
2,018	$ 101
2,019	101
2,020	3
2,021	3
2,022	2
Intangible assets, net	$ 210	$ 746

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Accrued Liabilities and Other Liabilities [Abstract]
Accrued employee compensation	$ 2,989	$ 4,037
Deferred rent	115	101
Accrued legal expense	1,231	710
Accrued consulting expense	115	104
Accrued vendor charges	912	1,396
Accrued revenue share expense	968	992
Accrued clinical trial expense	196	256
Accrued other	1,194	896
Total	$ 7,720	$ 8,492

Commitments and Contingencies62

Commitments and Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	$ 1,521
2,019	1,558
2,020	1,595
2,021	1,633
2,022	1,397
2023-2025	2,939
Total	10,643
Rent expense	1,700	$ 1,500	$ 1,600
Deferred rent	$ 800	$ 300	$ 400

Commitments and Contingencies63

Commitments and Contingencies (Details 2) $ in Millions	Oct. 31, 2017patentpetition	Aug. 09, 2017ft²	Mar. 09, 2017patent	Jul. 25, 2016USD ($)ft²extension	May 27, 2016defensepatent	Feb. 29, 2016patent	Sep. 30, 2011	Mar. 01, 2017patentpetition	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
License and revenue share agreements
Renewal term				5 years
Additional leased area (square feet) | ft²				18,223
Rent expense | $				$ 0.2
Number of renewal options | extension				1
Annual increase in initial base rental rate				2.00%
Number of Company's patents allegedly infringed upon						9
Number of affirmative defenses alleged | defense					2
Number of patents allegedly infringed					10
Number of petitions filed requesting Inter Partes Review | petition								16
Number of patents included in petition requesting Inter Partes Review								9
Patents dismissed from lawsuit			2
Number of petitions requesting inter partes review granted | petition	7
Number of petitions requesting inter partes review denied | petition	7
Number of petitions requesting inter partes review partially granted and denied | petition	2
Petitions granted number of patents	6
Number of patents remaining in lawsuit	5
Number of patents no longer in lawsuit	1
Petitions denied, number of patents	3
Number of patents remaining in lawsuit	2
Number of patents no longer in lawsuit	1
Number of petitions denied and requesting rehearing | petition	3
Petitions denied request for reexamination, number of patents	2
Revenue share agreements
License and revenue share agreements
Revenue share expense | $									$ 3.7	$ 3.5	$ 3.2
Revenue share expense as a percentage of product revenues									4.80%	4.40%	5.00%
Members of scientific advisory board | Revenue share agreements | Minimum
License and revenue share agreements
Required payment to related party from net revenues of current and planned products (as a percent)									10.00%
Members of scientific advisory board | Revenue share agreements | Maximum
License and revenue share agreements
Required payment to related party from net revenues of current and planned products (as a percent)									133.00%
Dr. Philipp Lang | Revenue share agreements
License and revenue share agreements
Revenue share expense | $									$ 1	$ 1	$ 0.8
Dr. Philipp Lang | Revenue share agreements | Minimum
License and revenue share agreements
Required payment to related party from net revenues of current and planned products (as a percent)							87.50%
Dr. Philipp Lang | Revenue share agreements | Maximum
License and revenue share agreements
Required payment to related party from net revenues of current and planned products (as a percent)							133.00%
iUni and iDuo
License and revenue share agreements
Number of patents allegedly infringed					2
iTotal
License and revenue share agreements
Number of patents allegedly infringed					3
iUni, iDuo, and iTotal
License and revenue share agreements
Number of patents allegedly infringed			8		5
Wallingford Lease
License and revenue share agreements
Renewal term		5 years
Additional leased area (square feet) | ft²		4,099
Additional extension option renewal term		2 years
Additional extension option past first extension term		3 years

Commitments and Contingencies64

Commitments and Contingencies (Details 3) $ in Thousands	Dec. 31, 2017USD ($)
Contractual Obligation, Fiscal Year Maturity [Abstract]
Other commitment	$ 1,435
Other commitment due in next twelve months	378
Other commitment due in second and third year	756
Other commitment due in fourth and fifth year	301
Other commitment due thereafter	$ 0

Debt and Notes Payable (Schedul

Debt and Notes Payable (Schedule of Long Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt and Notes Payable
Long-term debt gross	$ 30,000	$ 0
Amortized debt issuance costs	(333)	0
Long-term debt, less debt issuance costs	29,667	0
Oxford Finance L L C | Term loan | Oxford Finance, LLC, Term A Loan
Debt and Notes Payable
Long-term debt gross	15,000	$ 0
Oxford Finance L L C | Term loan | Oxford Finance, LLC, Term B Loan
Debt and Notes Payable
Long-term debt gross	$ 15,000

Debt and Notes Payable (Maturit

Debt and Notes Payable (Maturities of Long Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
2,018	$ 0
2,019	0
2,020	13,750
2,021	15,000
2,022	1,250
Total	$ 30,000	$ 0

Debt and Notes Payable (Details

Debt and Notes Payable (Details) - 2017 Secured Loan Agreement - Term loan - USD ($)	Jan. 06, 2017	Sep. 30, 2017	Jan. 31, 2017
Credit facility
Maximum amount committed by the lenders under the loan and security agreement	$ 50,000,000
Credit facility term	5 years
Basis spread on variable rate	0.53%
Final payment, percent of amount of loans advanced	5.00%
Events of default, additional interest rate	5.00%
Events of default, threshold amount	$ 500,000
Oxford Term Loan
Credit facility
Maximum amount committed by the lenders under the loan and security agreement	15,000,000
Amount drawn down	15,000,000
Oxford Finance, LLC, Term B Loan
Credit facility
Maximum amount committed by the lenders under the loan and security agreement		$ 15,000,000	$ 15,000,000
Oxford Term Loan C
Credit facility
Maximum amount committed by the lenders under the loan and security agreement	$ 20,000,000	$ 20,000,000
LIBOR
Credit facility
Basis spread on variable rate	6.47%

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	1 Months Ended	12 Months Ended			105 Months Ended	117 Months Ended
	Sep. 30, 2011	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2016
Revenue share agreements
Related Party Transaction
Revenue share expense		$ 3,700,000	$ 3,500,000	$ 3,200,000
Affiliate | Vertegen | License agreement
Related Party Transaction
Initial royalty rate on net sales of products under the agreement (as a percent)		6.00%
Reduced royalty rate on net sales of products following expiration of patents (as a percent)		3.00%
Royalty payments		$ 0
Expenses in connection with preparation of patent applications			150,000		$ 140,000	$ 150,000
Affiliate | Vertegen | License agreement | United States
Related Party Transaction
Period for reduced royalty rate		5 years
Dr. Philipp Lang | Revenue share agreements
Related Party Transaction
Revenue share expense		$ 1,000,000	$ 1,000,000	$ 800,000
Dr. Philipp Lang | Revenue share agreements | Minimum
Related Party Transaction
Required payment to related party from net revenues of current and planned products (as a percent)	87.50%
Dr. Philipp Lang | Revenue share agreements | Maximum
Related Party Transaction
Required payment to related party from net revenues of current and planned products (as a percent)	133.00%

Stockholders' Equity (Details T

Stockholders' Equity (Details Textual)	Jun. 16, 2015	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)shares	Jul. 07, 2015$ / sharesshares
Stockholders' Equity
Period for unrecognized compensation expense to be recognized		3 years 1 month 10 days
Stock-based compensation expense | $		$ 6,048,000	$ 5,324,000	$ 3,607,000
Common stock
Issuance of common stock (in shares)		228,946
Stock issued during period, acquisitions (in shares)		169,096
Common stock dividends declared to date | $		$ 0
Common stock, shares outstanding, beginning balance (in shares)		43,399,547	41,110,127
Issuance of common stock - option & warrant exercises		535,734	1,485,401
Issuance of restricted common stock		1,195,196	804,019
Issuance of common stock - preferred stock conversion to common stock		25,904,241
Common stock, shares outstanding, ending balance (in shares)		45,528,519	43,399,547	41,110,127
Preferred stock
Preferred stock, shares authorized		5,000,000	5,000,000		5,000,000
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.00001	$ 0.00001
Preferred stock, shares issued		0	0
Preferred stock, shares outstanding		0	0
Common Stock
Common stock
Reverse stock split ratio	1
Issuance of common stock (in shares)		228,946		10,350,000
Stock issued during period, acquisitions (in shares)		169,096
Common stock, shares outstanding, beginning balance (in shares)		43,399,547	41,110,127	4,286,164
Issuance of common stock - preferred stock conversion to common stock				25,904,241
Common stock, shares outstanding, ending balance (in shares)		45,528,519	43,399,547	41,110,127
Preferred stock
Preferred stock, par value (in dollars per share) | $ / shares					$ 0.00001
Restricted stock awards
Stockholders' Equity
Period for unrecognized compensation expense to be recognized		2 years 11 months 9 days
Restricted stock awards | Common Stock
Common stock
Issuance of common stock (in shares)		1,195,196	804,019	174,530

Stockholders' Equity (Schedule

Stockholders' Equity (Schedule of Stock by Class) (Details) $ in Millions	Dec. 31, 2017USD ($)occasion
Registration Rights Agreement, Other Than Form S-3
Demand registration rights
Minimum ownership of outstanding shares for holders to exercise demand registration rights (as a percent)	25.00%
Minimum offering relative to outstanding shares to trigger demand registration rights (as a percent)	20.00%
Minimum aggregate offering price to trigger demand registration rights | $	$ 20
Maximum number of registration statements under demand registration rights | occasion	2
Registration Rights Agreement, Form S-3
Demand registration rights
Minimum ownership of outstanding shares for holders to exercise demand registration rights (as a percent)	25.00%
Minimum offering relative to outstanding shares to trigger demand registration rights (as a percent)	25.00%
Minimum aggregate offering price to trigger demand registration rights | $	$ 5
Maximum number of registration statements under demand registration rights | occasion	1

Stockholders' Equity (Class of

Stockholders' Equity (Class of Warrant or Right) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Stock warrant activity
Number of warrants, cancelled/expired (in shares)	(142,857)
Weighted average exercise price, cancelled/expired (in dollars per share)	$ 7
Weighted average price, cancelled/expired (in dollars per share)	$ 7
Preferred stock warrants | Series C convertible preferred stock
Stock warrant activity
Number of warrants, outstanding at beginning of period (in shares)	0
Number of warrants, outstanding at end of period (in shares)	0	0
Common stock warrants
Stock warrant activity
Number of warrants, outstanding at beginning of period (in shares)	171,783	751,779
Number of warrants, exercised (in shares)		(166,665)
Number of warrants, cancelled/expired (in shares)		(413,331)
Number of warrants, outstanding at end of period (in shares)	28,926	171,783	751,779
Weighted average exercise price, outstanding at beginning of period	$ 7.47	$ 10.30
Weighted average exercise price, exercised (in dollars per share)		9
Weighted average exercise price, cancelled/expired (in dollars per share)		0
Weighted average exercise price, outstanding at end of period	$ 9.80	$ 7.47	$ 10.30
Number of exercisable warrants, outstanding at beginning of period (in shares)	171,783	751,779
Number of exercisable warrants, exercised (in shares)		(166,665)
Number of exercisable warrants, canceled/expired (in shares)	(142,857)	(413,331)
Number of exercisable warrants, outstanding at end of period (in shares)	28,926	171,783	751,779
Weighted average price, outstanding at beginning of period (in dollars per share)	$ 7.47	$ 10.30
Weighted average price, exercised (in dollars per share)		9
Weighted average price, cancelled/expired (in dollars per share)		0
Weighted average price, outstanding at end of period (in dollars per share)	$ 9.80	$ 7.47	$ 10.30
Weighted average contractual life	5 years 7 months 28 days	1 year 7 months 13 days	1 year 3 months 29 days
Warrants | Minimum
Assumptions used in estimating fair value of warrants at date of grant
Risk-free interest rate (as a percent)			0.91%
Expected term			2 years 6 months
Expected volatility (as a percent)			50.00%
Warrants | Maximum
Assumptions used in estimating fair value of warrants at date of grant
Risk-free interest rate (as a percent)			1.71%
Expected term			5 years
Expected volatility (as a percent)			55.00%

Stockholders' Equity (Schedul72

Stockholders' Equity (Schedule of Share-based Compensation Arrangements by Share-based Payment Award) (Details) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Jun. 30, 2015	May 31, 2015program	Feb. 28, 2011	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Aggregate Intrinsic Value
Exercised | $				$ 1,688	$ 8,219	$ 5,691
Balance outstanding at the end of the period | $				96	$ 8,547	$ 61,741
Total vested and exercisable | $				96
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Weighted average grant date fair value, vested | $				$ 1,600
Weighted average remaining contractual term, vested and exercisable				5 years 9 months 29 days
Weighted average remaining contractual term, outstanding				4 years 8 months 9 days
Stock options
Number of Options
Balance outstanding at the beginning of the period (in shares)				3,790,040	5,248,329	5,355,567
Granted (in shares)				963,350	179,178	403,086
Exercised (in shares)				(535,734)	(1,467,692)	(383,458)
Expired (in shares)				(466,210)	(81,251)	(30,876)
Cancelled/Forfeited (in shares)				(123,451)	(88,524)	(95,990)
Balance outstanding at the end of the period (in shares)				3,627,995	3,790,040	5,248,329
Total vested and exercisable (in shares)				2,696,151
Weighted Average Exercise Price per Share
Balance at the beginning of the period (in dollars per share) | $ / shares				$ 6.60	$ 5.56	$ 4.87
Granted (in dollars per shares) | $ / shares				4.95	8.78	12.20
Exercised (in dollars per share) | $ / shares				3.94	2.78	2.10
Expired (in dollars per share) | $ / shares				7.17	9.70	5.97
Cancelled/Forfeited (in dollars per share) | $ / shares				6.54	9.93	7.42
Balance at the end of the period (in dollars per share) | $ / shares				6.48	$ 6.60	$ 5.56
Total vested and exercisable | $ / shares				$ 6.66
Restricted stock awards
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Weighted average grant date fair value, vested | $				$ 5,500
2004 Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Expiration period			10 years
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity programs | program		2
2011 Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
Expiration period	10 years
2015 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance, before transfers and annual increases (in shares)				2,000,000
Maximum annual increase in common stock available for issuance (in shares)				3,000,000
Maximum annual increase in common stock available for issuance (as a percent)				3.00%
Common stock available for future issuance (in shares)				1,051,471
2015 Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period				4 years
Expiration period				10 years

Stockholders' Equity (Schedul73

Stockholders' Equity (Schedule of Restricted Common Stock Award Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted Average Fair Value
Weighted average grant date fair value, vested	$ 1.6
Restricted stock awards
Number of Shares
Unvested beginning of period (in shares)	911,710	174,530	0
Granted (in shares)	1,421,364	873,589	174,530
Vested (in shares)	(767,785)	(66,839)
Forfeited (in shares)	(226,168)	(69,570)
Unvested end of period (in shares)	1,339,121	911,710	174,530
Weighted Average Fair Value
Unvested beginning of period (in dollars per share)	$ 10.32	$ 22.31	$ 0
Granted (in dollars per share)	4.20	8.61	22.31
Vested (in dollars per share)	7.11	17.72
Forfeited (in dollars per share)	7.36	11.83
Unvested end of period (in dollars per share)	$ 6.06	$ 10.32	$ 22.31
Weighted average grant date fair value, vested	$ 5.5

Stockholders' Equity (Fair Valu

Stockholders' Equity (Fair Value of Options at Date of Grant) (Details) - Stock options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average fair value of options granted	$ 2.49	$ 4.46	$ 5.52
Assumptions used to estimate the fair value of options at date of grant
Risk-free interest rate, minimum (as a percent)	2.10%	1.98%	1.37%
Risk-free interest rate, maximum (as a percent)	2.30%		1.77%
Expected term		6 years 3 months
Dividend yield	0.00%	0.00%	0.00%
Expected volatility (as a percent)		51.00%
Minimum
Assumptions used to estimate the fair value of options at date of grant
Expected term	6 years 7 days		5 years 5 months 19 days
Expected volatility (as a percent)	51.00%		49.00%
Maximum
Assumptions used to estimate the fair value of options at date of grant
Expected term	6 years 3 months		6 years 5 months 12 days
Expected volatility (as a percent)	53.00%		50.00%

Stockholders' Equity (Schedul75

Stockholders' Equity (Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based compensation
Stock-based compensation expense	$ 6,048	$ 5,324	$ 3,607
Unrecognized compensation expense	$ 2,600
Period for unrecognized compensation expense to be recognized	3 years 1 month 10 days
Cost of revenues
Share-based compensation
Stock-based compensation expense	$ 441	333	239
Sales and marketing
Share-based compensation
Stock-based compensation expense	919	1,197	730
Research and development
Share-based compensation
Stock-based compensation expense	1,920	1,466	784
General and administrative
Share-based compensation
Stock-based compensation expense	2,768	$ 2,328	$ 1,854
Restricted stock awards
Share-based compensation
Unrecognized compensation expense	$ 0
Period for unrecognized compensation expense to be recognized	2 years 11 months 9 days

Income Taxes Income Taxes (Deta

Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S.	$ (53,274)	$ (51,576)	$ (50,155)
Non‑U.S.	(144)	(5,949)	(7,050)
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest	$ (53,418)	$ (57,525)	$ (57,205)

Income Taxes (Schedule of Incom

Income Taxes (Schedule of Income Before Income Tax, Domestic and Foreign) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loss before income taxes:
U.S.	$ (53,274)	$ (51,576)	$ (50,155)
Non‑U.S.	(144)	(5,949)	(7,050)
Loss before income taxes	$ (53,418)	$ (57,525)	$ (57,205)

Income Taxes (Schedule of Effec

Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 0	$ 0	$ 0
State	0	0	0
Foreign	125	63	41
Total current tax expense (benefit)	125	63	41
Deferred:
Federal	31	0	0
State	6	0	0
Foreign	0	0	0
Total deferred tax expense (benefit)	37	0	0
Total	$ 162	$ 63	$ 41
Tax at U.S. statutory rate	(34.00%)	(34.00%)	(34.00%)
State taxes, net of federal benefits	(3.12%)	(2.70%)	(2.27%)
Permanent items	1.96%	0.42%	1.52%
Tax credit	(1.35%)	(1.06%)	(0.85%)
Change in valuation allowance	(54.85%)	33.95%	31.07%
Foreign rate differential	(0.17%)	1.04%	1.68%
Rate change	90.78%	(0.06%)	0.01%
Uncertain tax positions	0.41%	2.06%	2.21%
Other	0.64%	0.46%	0.70%
Effective income tax rate	0.30%	0.11%	0.07%

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Federal and state net operating loss carryforwards	$ 90,437	$ 115,719
Foreign net operating loss carryforwards	2,561	2,561
Accrued expenses	157	280
Credits	6,055	5,091
Deferred revenue	1,068	1,709
Stock compensation expense	1,805	2,946
Other	2,111	2,757
Total deferred tax assets	104,194	131,063
Valuation allowance	(103,430)	(130,005)
Net deferred tax assets	764	1,058
Deferred tax liabilities:
Fixed assets	(664)	(841)
Intangibles	(134)	(217)
Other	(3)	0
Net deferred tax liabilities	(801)	(1,058)
Net deferred tax liabilities	$ (37)	$ 0

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 103,430,000	$ 130,005,000
Decrease in valuation allowance	26,600,000
Unrecognized tax benefits	5,136,000	4,918,000	$ 3,730,000	$ 2,466,000
Unrecognized tax benefits, amount netted against deferred tax assets	4,900,000	4,800,000
Cumulative effect of new accounting principle in period of adoption		0
Decrease in deferred tax assets due to change in tax rate	48,500,000
Decrease in deferred tax asset valuation allowance due to change in tax rate	48,500,000
Net impact of change in tax rate on deferred tax assets	0
Tax benefit on deferred tax liabilities due to change in tax rate	19,000
Transition tax on foreign earnings	0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	373,600,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		198,900,000
Germany | Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	25,000,000
Accounting Standards Update 2016-09 | Deferred Tax Asset
Operating Loss Carryforwards [Line Items]
Cumulative effect of new accounting principle in period of adoption	$ 7,700,000	7,700,000
Accounting Standards Update 2016-09 | Valuation Allowance of Deferred Tax Assets
Operating Loss Carryforwards [Line Items]
Cumulative effect of new accounting principle in period of adoption		(7,700,000)
Retained Earnings
Operating Loss Carryforwards [Line Items]
Cumulative effect of new accounting principle in period of adoption		311,000
Retained Earnings | Accounting Standards Update 2016-09
Operating Loss Carryforwards [Line Items]
Cumulative effect of new accounting principle in period of adoption		$ 0

Income Taxes (Schedule of Unrec

Income Taxes (Schedule of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Unrecognized tax benefits beginning of year	$ 219	$ 1,187	$ 1,264
Gross change for current year positions	4,918	3,730	2,466
Decrease for prior period positions	$ 5,136	$ 4,918	$ 3,730

Segment and Geographic Data (De

Segment and Geographic Data (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Segment Reporting [Abstract]
Number of reportable segments | segment	1
Geographic information for Product Revenue and Property and equipment, net
Product Revenue	$ 77,100	$ 78,921	$ 62,791
Property and equipment, net	16,514	15,084
United States
Geographic information for Product Revenue and Property and equipment, net
Product Revenue	64,390	62,366	47,223
Property and equipment, net	16,424	14,971
Germany
Geographic information for Product Revenue and Property and equipment, net
Product Revenue	11,217	14,701	13,795
Rest of World
Geographic information for Product Revenue and Property and equipment, net
Product Revenue	1,493	1,854	$ 1,773
Property and equipment, net	$ 90	$ 113

Employee Savings Plan (Details)

Employee Savings Plan (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Maximum annual contributions per employee, percent	80.00%
Employer matching contribution, percent of match	50.00%
Employer matching contribution, percent of employees' gross pay	4.00%
Employer discretionary contribution amount	$ 457	$ 478	$ 400

Selected Quarterly Financial 84

Selected Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue
Total revenue	$ 20,751	$ 18,425	$ 18,484	$ 20,455	$ 21,673	$ 18,643	$ 19,333	$ 20,250	$ 78,115	$ 79,899	$ 66,887
Gross profit	8,757	7,314	6,248	6,495	8,045	5,998	6,001	6,663	28,814	26,707	21,785
Net loss	$ (11,858)	$ (12,472)	$ (12,090)	$ (17,160)	$ (15,740)	$ (12,762)	$ (14,052)	$ (15,034)	$ (53,580)	$ (57,588)	$ (57,246)
Per Share Data:
Net loss per share - basic and diluted	$ (0.27)	$ (0.29)	$ (0.28)	$ (0.40)	$ (0.37)	$ (0.31)	$ (0.34)	$ (0.37)	$ (1.24)	$ (1.39)	$ (2.60)

Subsequent Events Subsequent Ev

Subsequent Events Subsequent Events (Details) - Subsequent Event $ / shares in Units, $ in Millions	Jan. 29, 2018USD ($)$ / sharesshares
Subsequent Event [Line Items]
Sale of stock (in dollars per share) | $ / shares	$ 1.50
Shelf Registration Statement
Subsequent Event [Line Items]
Number of shares issued (in shares)	15,333,333
Sale of stock net proceeds | $	$ 21.3
Over-Allotment Option
Subsequent Event [Line Items]
Number of shares issued (in shares)	2,000,000