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Related Party Transaction [Line Items] Related Party Transaction [Line Items] Unsecured convertible loan Convertible Debt Convertible preferred stock amount on conversion Extinguishment of Debt, Amount Percentage of conversion price discount on common stock Discount On Conversion Price Discount On Conversion Price Accounting Policies [Abstract] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Schedule of Earnings Per Share, Basic, by Common Class, Including Two Class Method [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated Deficit Retained Earnings [Member] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items] Net loss Net Income (Loss) Attributable to Parent Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share 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Issuance of common stock under stock plans (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Issuance of common stock under stock plans Stock Issued During Period, Value, Stock Options Exercised Issuance of common stock under ESPP Stock Issued During Period, Value, Employee Stock Purchase Plan Stock-based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Unrealized loss on available-for-sale securities, net of taxes Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Net loss Ending balance Ending balance (in shares) Commitments Commitments and Contingencies Disclosure [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] One-month LIBOR One-month 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Terms, Proceeds from Sale of Common Stock Debt stated interest rate Debt Instrument, Interest Rate, Stated Percentage Debt basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Debt term Debt Instrument, Term Debt effective interest rate Debt Instrument, Interest Rate, Effective Percentage Debt termination payment percentage Debt Instrument, Termination Payment, Percentage Debt Instrument, Termination Payment, Percentage Repayments of notes payable Repayments of Notes Payable Proceeds from sale of stock, convertible subordinated notes, collaboration agreements, grants or development contracts Debt Instrument, Debt Agreement Terms, Proceeds from Sale of Stock, Convertible Subordinated Notes, Collaboration Agreements, Grants or Development Contracts Debt Instrument, Debt Agreement Terms, Proceeds from Sale of Stock, Convertible Subordinated Notes, Collaboration Agreements, Grants or Development Contracts Enrollment in trial Debt Instrument, Debt Agreement Terms, Enrollment in Trial Debt Instrument, Debt Agreement Terms, Enrollment in Trial Repayment term Debt Instrument, Debt Agreement Terms, Repayment Term Debt Instrument, Debt Agreement Terms, Repayment Term Covenant, increase in interest rate in event of default Debt Instrument, Covenant, Increase in Interest Rate in Event of Default Debt Instrument, Covenant, Increase in Interest Rate in Event of Default Warrants to purchase shares of stock, shares Fair value of warrants Warrants and Rights Outstanding Interest expense on debt Interest Expense, Debt Debt maximum amount available Debt Instrument, Maximum Amount Available Debt Instrument, Maximum Amount Available Debt conversion price Debt Instrument, Convertible, Conversion Price Convertible preferred stock issued on conversion Conversion of Stock, Shares Issued Unused borrowing capacity, fee Debt Instrument, Unused Borrowing Capacity, Fee Debt instrument, final fee Debt Instrument, Final Fee Debt Instrument, Final Fee Payment of final fee 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Stock, Gross of Issuance Costs Proceed from Issuance of Common Stock, Gross of Issuance Costs Shares issued for underwriters' granted of their over-allotment option (in shares) Stock Issued During Period Shares To Underwriters For Exercise Of Over Allotment Option Stock Issued During Period Shares To Underwriters For Exercise Of Over Allotment Option Proceeds from initial public offering, net of issuance costs Proceeds from Issuance Initial Public Offering Conversion of preferred stock to common stock upon initial public offering (in shares) Cash, cash equivalents and short-term investments Cash, Cash Equivalents, and Short-term Investments Accumulated deficit Retained Earnings (Accumulated Deficit) Statement of Financial Position [Abstract] Common stock, par value Common Stock, Par or Stated Value Per Share Common stock, shares authorized Common Stock, Shares Authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Preferred stock, par value Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Deferred Tax Assets, Net [Abstract] Deferred Tax Assets, Net [Abstract] Net operating loss carry forwards Deferred Tax Assets, Operating Loss Carryforwards Research and development credit Deferred Tax Assets, Tax Credit Carryforwards, Research Intangible assets Deferred Tax Assets, Goodwill and Intangible Assets Depreciation Deferred Tax Assets, Property, Plant and Equipment Other Deferred Tax Assets, Other Gross Deferred tax assets Deferred Tax Assets, Gross Less: valuation allowance Deferred Tax Assets, Valuation Allowance Net deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Fair Value Measurements Fair Value Disclosures [Text Block] Income Taxes Income Tax Disclosure [Text Block] 2014 Employment Commencement Incentive Plan Two Thousand Fourteen Employment Commencement Incentive Plan [Member] Two Thousand Fourteen Employment Commencement Incentive Plan [Member] Shares Available for grant Share-based Compensation Arrangement by Share-based Payment Award, Options, Shares Available For Grant [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Options, Shares Available For Grant [Abstract] Beginning balance Options granted Options exercised Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant Exercised In Period Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant Exercised In Period Options forfeited Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Option expired Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period RSUs granted RSUs cancelled Ending balance Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Beginning balance Options granted Options exercised Options forfeited Option expired Ending balance Vested and exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number Vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Weighted-Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning balance Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Options granted Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Options exercised Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Options forfeited Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Option expired Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Ending balance Vested and exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price Vested and expected to vest Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Weighted-Average Remaining Contractual Life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Outstanding options, weighted-average remaining contractual life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Options vested and exercisable, weighted-average remaining contractual life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term Options vested and expected to vest, weighted-average remaining contractual life (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Options exercised, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Outstanding options, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Options vested and exercisable, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Aggregate Intrinsic Value Options vested and expected to vest, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value 2016 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2017 Long-term Debt, Maturities, Repayments of Principal in Year Two 2018 Long-term Debt, Maturities, Repayments of Principal in Year Three 2019 Long-term Debt, Maturities, Repayments of Principal in Year Four Total principal payments Long-term Debt, Maturities, Repayments of Principal, Total Long-term Debt, Maturities, Repayments of Principal, Total Final fee due at maturity in 2019 Total principal and final fee payments Long-term Debt, Maturities, Repayments of Principal and Final Fee, Total Long-term Debt, Maturities, Repayments of Principal and Interest, Present Value Unamortized discount and debt issuance costs Debt Instrument, Unamortized Discount and Debt Issuance Costs Debt Instrument, Unamortized Discount and Debt Issuance Costs Loan payable, long term Long-term Debt Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Depreciation and amortization expense Depreciation, Depletion and Amortization Accrued clinical and development expenses Accrued Clinical And Development Expenses Accrued Clinical And Development Expenses Payroll and related bonus expenses Employee-related Liabilities, Current Other Other Accrued Liabilities, Current Accrued liabilities, current Accrued Liabilities, Current Schedule of Weighted Average Number of Shares Schedule of Weighted Average Number of Shares [Table Text Block] Schedule of Potentially Dilutive Securities Outstanding Excluded from the Computations of Diluted Weighted-Average Shares Outstanding Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Short-term investments Short-term Investments Prepaids and other current assets Prepaid Expense and Other Assets, Current Total current assets Assets, Current Property and equipment, net Restricted cash Restricted Cash and Cash Equivalents, Noncurrent Deposit and other assets Other Assets, Noncurrent Total assets Assets Liabilities and Stockholders’ Equity Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued liabilities Other current liabilities Other Liabilities, Current Total current liabilities Liabilities, Current Loan payable, long-term Notes Payable, Noncurrent Other long-term liabilities Liabilities, Other than Long-term Debt, Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments and Contingencies Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Common stock, $0.001 par value, 290,000,000 shares authorized, 18,395,219 and 17,907,135 shares issued and outstanding at December 31, 2015 and 2014, respectively Common Stock, Value, Issued Preferred stock, $0.001 par value, 10,000,000 shares authorized, no shares issued and outstanding Preferred Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Accumulated deficit Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity Total liabilities and stockholders’ equity Liabilities and Equity Stock holders' Equity and Convertible Preferred Stock Preferred Stock [Text Block] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Research and Development Research and Development Expense [Member] General and Administrative General and Administrative Expense [Member] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items] Total stock-based compensation expense Allocated Share-based Compensation Expense Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Income Statement [Abstract] Operating expenses: Operating Expenses [Abstract] General and administrative General and Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income (Loss) Interest expense Interest Expense Other income, net Other Nonoperating Income (Expense) Net loss Weighted-average common shares outstanding used to calculate basic and diluted net loss per common share (in shares) Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Facilities related and other costs Facilities and Other Restructuring [Member] Facilities and Other Restructuring [Member] Impairment of Asset Impairment of Asset [Member] Impairment of Asset [Member] Facility Closing Facility Closing [Member] General and administrative expense Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Charges during the period Restructuring Charges Cash from asset disposal Proceeds from Sale of Other Assets Accrued facility charges Payments for Rent License and Collaboration Agreements Collaborative Arrangement Disclosure [Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive loss: Other Comprehensive Income (Loss), Net of Tax [Abstract] Net unrealized losses on available-for-sale securities Total comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Schedule of Stockholders' Equity Note, Warrants or Rights Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block] Facility lease expiration date Lease Expiration Date Number of operating segments Number of Operating Segments Allowance for doubtful accounts receivable Allowance for Doubtful Accounts Receivable Property, plant and equipment, useful life Property, Plant and Equipment, Useful Life Impairment charges Organization and Basis of Presentation and Consolidation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Derivative liability Derivative Liability, Noncurrent Deferred rent Deferred Rent, Noncurrent Deferred Rent, Noncurrent Other Long-term Liabilities, Total Contract revenue Revenues Operating expenses Interest and other income (expense), net Basic and diluted net loss per common share (in dollars per share) Income (Loss) from Continuing Operations, Per Basic and Diluted Share Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Commercial Paper Commercial Paper [Member] US Treasury Bill Securities US Treasury Bill Securities [Member] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, 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Equivalents, Restricted Cash Noncurrent, and Available-for-Sale Securities Liabilities Liabilities, Fair Value Disclosure [Abstract] Statement of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Amortization of premium on short-term investments Accretion (Amortization) of Discounts and Premiums, Investments Stock-based compensation expense Revaluation of convertible preferred stock warrant Fair Value Adjustment of Warrants Revaluation of derivative liability Revaluation of Derivative Liability Revaluation of Derivative Liability Loss on asset disposition Gain (Loss) on Disposition of Assets Non-cash interest expense relating to notes payable Non-cash interest expense relating to related-party convertible loan payable Interest Expense, Related Party Non-cash restructuring charges Impairment of Leasehold Change in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Contracts receivable Increase (Decrease) in Contract Receivables, Net Prepaids and other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable and accrued liabilities Increase (Decrease) in Accounts Payable and Accrued Liabilities Other liabilities Increase (Decrease) in Other Operating Liabilities Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations Cash flows from investing activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Purchase of property and equipment Payments to Acquire Property, Plant, and Equipment Purchase of short-term investments Payments to Acquire Available-for-sale Securities Maturities and sale of short-term investments Proceeds from Sale, Maturity and Collection of Short-term Investments Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Cash flows from financing activities: Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Proceeds from the issuance of common stock in connection with equity incentive plans Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options Proceeds from exercise of stock warrants Proceeds from Warrant Exercises Repayment of notes payable Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net increase in cash and cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents, beginning of year Cash and cash equivalents, end of year Supplemental disclosures of cash flow information Supplemental Cash Flow Information [Abstract] Interest paid Interest Paid Supplemental disclosures of noncash investing and financing information Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Conversion of related-party convertible loan and notes payable to convertible preferred stock Debt Conversion, Original Debt, Amount Conversion of convertible preferred stock into common stock