Entity Central Index Key Document and entity information. 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 Current Fiscal Year End Date Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Well Known Seasoned Issuer Entity Current Reporting Status Entity Current Reporting Status Entity Voluntary Filers Entity Voluntary Filers Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity Public Float Entity Public Float Statement Of Financial Position [Abstract] 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 Restricted cash Restricted Cash And Cash Equivalents At Carrying Value Prepaid expenses and other current assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net Restricted cash Restricted Cash And Cash Equivalents Noncurrent Long-term investments Long Term Investments Other assets Other Assets Noncurrent Total assets Assets Liabilities and Stockholders’ Equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued liabilities Accrued Liabilities Current Deferred rent—current portion Deferred Rent Credit Current Total current liabilities Liabilities Current Other liabilities Other Liabilities Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 12) Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock, par value of $0.001 per share—25,000,000 shares authorized; nil outstanding as of December 31, 2015 and 2014 Preferred Stock Value Common stock, par value of $0.001 per share—250,000,000 shares authorized; 38,882,394 and 31,934,682 shares issued and outstanding as of December 31, 2015 and 2014 Common Stock Value Additional paid-in capital Additional Paid In Capital Accumulated other comprehensive loss Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders’ equity Stockholders Equity Total liabilities and stockholders’ equity Liabilities And Stockholders Equity Preferred stock, par value Preferred Stock Par Or Stated Value Per Share Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares outstanding Preferred Stock Shares Outstanding 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 Common Stock Shares Outstanding Income Statement [Abstract] Operating expenses: Operating Expenses [Abstract] Research and development Research And Development Expense General and administrative General And Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income Loss Other income (expense), net: Nonoperating Income Expense [Abstract] Interest income Investment Income Interest Other expense, net Other Nonoperating Income Expense Total other income (expense), net Nonoperating Income Expense Net loss Net Income Loss Net loss attributable to common stockholders Net Income Loss Available To Common Stockholders Basic Net loss per share attributable to common stockholders, basic and diluted Earnings Per Share Basic And Diluted Shares used in computing net loss per share attributable to common stockholders, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Net loss Other comprehensive income (loss): Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Unrealized gain (loss) on available-for-sale securities Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Total comprehensive loss Comprehensive Income Net Of Tax Stock issued during period value secondary issues. Stock issued during period shares secondary issues. Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] Statement Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid In Capital [Member] Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income [Member] Accumulated Deficit Retained Earnings [Member] Deferred Compensation Arrangement With Individual Share Based Payments By Type Of Deferred Compensation Deferred Compensation Arrangement With Individual Share Based Payments By Type Of Deferred Compensation [Axis] Equity Based Arrangements Individual Contracts Type Of Deferred Compensation Equity Based Arrangements Individual Contracts Type Of Deferred Compensation [Domain] Employee Stock Option Employee Stock Option [Member] Founders stock. Founders Stock Founders Stock [Member] Statement Class Of Stock Statement Class Of Stock [Axis] Class Of Stock Class Of Stock [Domain] Series A redeemable convertible preferred stock. Series A Redeemable Convertible Preferred Stock Series A Redeemable Convertible Preferred Stock [Member] Series b convertible preferred stock. Series B Convertible Preferred Stock Series B Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Beginning balance Beginning balance, shares Beginning balance Temporary Equity Carrying Amount Attributable To Parent Beginning balance, shares Temporary Equity Shares Outstanding Conversion of convertible preferred stock to common stock at initial public offering Stock Issued During Period Value Conversion Of Convertible Securities Conversion of convertible preferred stock to common stock at initial public offering, shares Stock Issued During Period Shares Conversion Of Convertible Securities Reclassification of preferred stock warrant liability Adjustments To Additional Paid In Capital Increase In Carrying Amount Of Redeemable Preferred Stock Issuance of common stock in connection with initial public offering, net of issuance costs and preferred stock dividend Stock Issued During Period Value New Issues Issuance of common stock in connection with initial public offering, net of issuance costs and preferred stock dividend, shares Stock Issued During Period Shares New Issues Issuance of common stock in connection with underwritten public offering, net of issuance costs Stock Issued During Period Value Secondary Issues Issuance of common stock in connection with underwritten public offering, net of issuance costs, shares Stock Issued During Period Shares Secondary Issues Issuance of common stock upon exercise of stock options and warrants Stock Issued During Period Value Stock Options Exercised Issuance of common stock upon exercise of stock options and warrants , shares Stock Issued During Period Shares Stock Options Exercised Employee stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Accretion on convertible preferred stock Preferred Stock Accretion Of Redemption Discount Restricted stock units vested during the period, net Adjustments To Additional Paid In Capital Share Based Compensation Restricted Stock Units Requisite Service Period Recognition Restricted stock units vested during the period, net of shares Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Ending balance Ending balance, shares Ending balance Ending balance, shares Statement Of Cash Flows [Abstract] 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 Depreciation Depletion And Amortization Amortization of premium on investment securities Accretion Amortization Of Discounts And Premiums Investments Stock-based compensation Share Based Compensation Revaluation of convertible preferred stock warrant liability Fair Value Adjustment Of Warrants Changes in operating assets and liabilities: Increase Decrease In Operating Capital [Abstract] Prepaid expenses and other current assets Increase Decrease In Prepaid Deferred Expense And Other Assets Other assets Increase Decrease In Other Noncurrent Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses and other liabilities Increase Decrease In Accrued Liabilities And Other Operating Liabilities Net cash used in operating activities Net Cash Provided By Used In Operating Activities Continuing Operations 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 investments Payments To Acquire Available For Sale Securities Proceeds from sale of investments Proceeds From Sale Of Available For Sale Securities Proceeds from maturities of investments Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Decrease (increase) in restricted cash Increase Decrease In Restricted Cash Net cash used in investing activities Net Cash Provided By Used In Investing Activities Continuing Operations Financing activities: Net Cash Provided By Used In Financing Activities Continuing Operations [Abstract] Proceeds from issuance of common stock, net Proceeds From Issuance Of Common Stock Payment of preferred stock dividend Payments Of Dividends Preferred Stock And Preference Stock Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Net increase (decrease) in cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Cash and cash equivalents at beginning of year Cash and cash equivalents at end of year Supplemental disclosures of non-cash investing and financing information: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Costs of fixed assets included in accounts payable and accrued liabilities Capital Expenditures Incurred But Not Yet Paid Reclassification of warrant liability to equity upon conversion to common stock warrants Embedded Derivative No Longer Bifurcated Amount Reclassified To Stockholders Equity Conversion of Series A and Series B preferred stock to common stock Conversion Of Stock Amount Converted1 Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization and Basis of Presentation Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Text Block] Accounting Policies [Abstract] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Investments Debt And Equity Securities [Abstract] Balance Sheet Components Supplemental Balance Sheet Disclosures [Text Block] Collaborative arrangement and noncollaborative arrangement transactions disclosure. Research grant agreement. Research Grant Agreement [Abstract] License and Research Agreements Collaborative Arrangement And Noncollaborative Arrangement Transactions Disclosure [Text Block] Common stock warrants disclosure. Warrants And Rights Note Disclosure [Abstract] Common Stock Warrants Common Stock Warrants Disclosure [Text Block] Common Stock Disclosure. Common stock. Common Stock [Abstract] Common Stock Common Stock Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Awards Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Defined Contribution Pension And Other Postretirement Plans Disclosure [Abstract] Defined Contribution Plan Compensation And Employee Benefit Plans [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Earnings Per Share [Abstract] Net Loss per Share Attributable to Common Stockholders Earnings Per Share [Text Block] Quarterly Financial Data [Abstract] Quarterly Financial Data (unaudited) Quarterly Financial Information [Text Block] Basis of Consolidation Consolidation Policy [Text Block] Use of Estimates Use Of Estimates Cash and Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Investments Investment Policy [Text Block] Concentration of credit risk and other risks and uncertainties. Concentration of Credit Risk and Other Risks and Uncertainties Concentration Of Credit Risk And Other Risks And Uncertainties Policy [Text Block] Property and Equipment Property Plant And Equipment Policy [Text Block] Impairment of Long-Lived Assets Impairment Or Disposal Of Long Lived Assets Policy [Text Block] Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Accruals of research and development costs. Accruals of Research and Development Costs Accruals Of Research And Development Costs Policy [Text Block] Leases Lease Policy [Text Block] Comprehensive Loss Comprehensive Income Policy Policy [Text Block] Research and Development Research And Development Expense Policy Stock-Based Compensation Share Based Compensation Option And Incentive Plans Policy Income Taxes Income Tax Policy [Text Block] Net Loss per Share Attributable to Common Stockholders Earnings Per Share Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Summary of Outstanding Warrants Schedule Of Stockholders Equity Note Warrants Or Rights [Text Block] Effective Tax Rate of Provision for Income Taxes from Federal Statutory Rate Schedule Of Effective Income Tax Rate Reconciliation Table [Text Block] Property plant and equipment useful lives. Summary of Useful Lives of Property and Equipment Property Plant And Equipment Useful Lives Table [Text Block] Summary of Financial Assets Measured on Recurring Basis Fair Value Assets Measured On Recurring Basis [Text Block] Summary of Fair Values of Cash Equivalents, Short-Term Investments and Long-Term Investments Classified as Available-for-Sale Securities Schedule Of Cash Cash Equivalents And Short Term Investments Table [Text Block] Summary of Property and Equipment Property Plant And Equipment [Text Block] Accrued Liabilities Schedule Of Accrued Liabilities Table [Text Block] Schedule of reserved shares of common stock for future issuance. Schedule of Reserved Shares of Common Stock for Future Issuance Schedule Of Reserved Shares Of Common Stock For Future Issuance Table [Text Block] Summary of Activity Under Stock Option Plans Including 2011 Plan and 2014 Plan Schedule Of Other Share Based Compensation Activity Table [Text Block] Summary of Options Outstanding and Exercisable by Exercise Price Schedule Of Share Based Compensation Shares Authorized Under Stock Option Plans By Exercise Price Range [Text Block] Summary of Stock-Based Compensation Recognized Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Fair Value of Stock Option Awards Estimated Using Black-Scholes Option-Pricing Model Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Schedule of Tax Effect of Temporary Differences to Significant Portions of Deferred Tax Assets Schedule Of Deferred Tax Assets And Liabilities Table [Text Block] Unrecognized Tax Benefits Schedule Of Unrecognized Tax Benefits Roll Forward Table [Text Block] Summary of Future Minimum Lease Payments under Non-Cancellable Operating Leases Arrangements and Future Payments under Contractually Binding Manufacturing and Service Agreements Contractual Obligation Fiscal Year Maturity Schedule Table [Text Block] Computation of Basic and Diluted Net Loss per Share Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Outstanding Shares of Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Summary of Unaudited Quarterly Financial Information Schedule Of Quarterly Financial Information Table [Text Block] Lessee leasing arrangements operating leases commencement date. Discount on letter of credit on successful payment of lease amount. Operating lease expiration year.