Entity Central Index Key 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 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 Deferred offering costs non current. Lease incentive payable noncurrent. Preferred stock warrant liability. Statement Of Financial Position [Abstract] Statement [Table] Statement [Table] Statement Class Of Stock Statement Class Of Stock [Axis] Class Of Stock Class Of Stock [Domain] Convertible Preferred Stock Series A, A-2, B, C, D and D-1 [Member] Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Investments Short Term Investments 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 Deferred offering costs Deferred Offering Costs Non Current Deferred financing costs Deferred Finance Costs Noncurrent Net Total assets Assets Liabilities, Convertible Preferred Stock and Stockholders’ Equity (Deficit) Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued expenses and other current liabilities Accrued Liabilities And Other Liabilities Notes payable; current portion Notes Payable Current Total current liabilities Liabilities Current Lease incentive obligation Lease Incentive Payable Noncurrent Notes payable, net of discount Long Term Notes Payable Preferred stock warrant liability Preferred Stock Warrant Liability Total liabilities Liabilities Commitments and contingencies: Commitments And Contingencies Convertible preferred stock (Series A, A-2, B, C, D and D-1), value Temporary Equity Carrying Amount Attributable To Parent Stockholders’ equity (deficit): Stockholders Equity [Abstract] Common stock, $0.001 par value; 200,000,000 and 38,000,000 shares authorized at December 31, 2015 and 2014, respectively; 39,082,017 and 6,890,250 shares issued and outstanding at December 31, 2015 and 2014, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated deficit Retained Earnings Accumulated Deficit Total stockholders’ equity (deficit) Stockholders Equity Total liabilities, convertible preferred stock and stockholders’ equity (deficit) Liabilities And Stockholders Equity Convertible preferred stock, par value Temporary Equity Par Or Stated Value Per Share Convertible preferred stock, shares authorized Temporary Equity Shares Authorized Convertible preferred stock, shares issued Temporary Equity Shares Issued Convertible preferred stock, shares outstanding Temporary Equity Shares Outstanding Convertible preferred stock, liquidation preference Temporary Equity Liquidation Preference 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 Statement Of Income And Comprehensive Income [Abstract] Revenue Revenues Operating expenses: Operating Expenses [Abstract] Research and development expenses Research And Development Expense General and administrative expenses General And Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income Loss Other income (expense): Nonoperating Income Expense [Abstract] Interest income Interest Income Other Interest expense Interest Expense Other Revaluation of preferred stock warrant liability Fair Value Option Changes In Fair Value Gain Loss1 Total other income (expense), net Nonoperating Income Expense Net loss Net Income Loss Accretion of convertible preferred stock to redemption value Temporary Equity Accretion To Redemption Value Adjustment 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 Weighted average common shares outstanding, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Other comprehensive income (loss): Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Unrealized gain on investments, net of tax of $0 Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Total other comprehensive income Other Comprehensive Income Loss Net Of Tax Comprehensive loss Comprehensive Income Net Of Tax Unrealized loss on investment, tax Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Tax Temporary equity shares issued during period. Stock issued during period value common stock warrants exercised. Stock issued during period shares common stock warrants exercised. Temporary equity issuance cost. Statement Of Stockholders Equity [Abstract] Statement Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-in Capital [Member] Additional Paid In Capital [Member] Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive Income [Member] Accumulated Deficit [Member] Retained Earnings [Member] Series B convertible preferred stock. Series B Convertible Preferred Stock [Member] Series B Convertible Preferred Stock [Member] Series C convertible preferred stock. Series C Convertible Preferred Stock [Member] Series C Convertible Preferred Stock [Member] Series D and D-1 convertible preferred stock. Series D and D-1 Convertible Preferred Stock [Member] Series D And D1 Convertible Preferred Stock [Member] Series D convertible preferred stock. Series D Convertible Preferred Stock [Member] Series D Convertible Preferred Stock [Member] Stockholders' (deficit), value, beginning balance Stockholders' (deficit), shares, beginning balance Convertible preferred stock, value, beginning balance Convertible preferred stock, shares, beginning balance Repurchase of unvested restricted common stock Stock Repurchased During Period Shares Issuance of convertible preferred stock, net of issuance costs, value Temporary Equity Stock Issued During Period Value New Issues Issuance of convertible preferred stock, net of issuance costs, shares Temporary Equity Shares Issued During Period Issuance of common stock upon exercise of stock options, value Stock Issued During Period Value Stock Options Exercised Issuance of common stock upon exercise of stock options, shares Stock Issued During Period Shares Stock Options Exercised Issuance of common stock upon completion of initial public offering, net of offering costs, value Stock Issued During Period Value New Issues Issuance of common stock upon completion of initial public offering, net of offering costs, shares Stock Issued During Period Shares New Issues Issuance of common stock upon exercise of common stock warrant, value Stock Issued During Period Value Common Stock Warrants Exercised Issuance of common stock upon exercise of common stock warrant, shares Stock Issued During Period Shares Common Stock Warrants Exercised Stock-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Accretion of convertible preferred stock to redemption value Temporary Equity Accretion To Redemption Value Accretion of convertible preferred stock to redemption value, impact on permanent equity Increase In Carrying Amount Of Redeemable Preferred Stock Issuance costs of convertible preferred stock Temporary Equity Issuance Cost Reclassification of preferred stock warrant liability Adjustments To Additional Paid In Capital Warrant Issued Conversion of convertible preferred stock upon listing, value Stock Issued During Period Value Conversion Of Convertible Securities Conversion of convertible preferred stock upon listing, shares Stock Issued During Period Shares Conversion Of Convertible Securities Unrealized gain on investments Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Reclassification Adjustments Net Of Tax Net loss Stockholders' (deficit), value, ending balance Stockholders' (deficit), shares, ending balance Convertible preferred stock, value, ending balance Convertible preferred stock, shares, ending balance Issuance costs of convertible preferred stock Payment of license fees in common stock warrant. Proceeds from issuance of convertible preferred stock net of issuance costs. Proceeds from issuance of notes payable and preferred stock warrants net of issuance costs. Proceeds from issuance of common and restricted stocks. Issuance of warrants in connection with notes payable. 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] Stock-based compensation expense Share Based Compensation Depreciation and amortization expense Depreciation Depletion And Amortization Loss from revaluation of preferred stock warrant liability Fair Value Adjustment Of Warrants Licensing fees paid in common stock warrant Payment Of License Fees In Common Stock Warrant Other non-cash expense Other Noncash Expense 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 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 Cash flows from investing activities: Net Cash Provided By Used In Investing Activities Continuing Operations [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Purchases of Short-term investments Payments To Acquire Short Term Investments Maturities of Short-term investments Proceeds From Sale Maturity And Collections Of Investments Changes in restricted cash Increase Decrease In Restricted Cash Net cash 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 issuance of convertible preferred stock, net of issuance costs Proceeds From Issuance Of Convertible Preferred Stock Net Of Issuance Costs Proceeds from issuance of notes payable and preferred stock warrant, net of issuance costs Proceeds From Issuance Of Notes Payable And Preferred Stock Warrants Net Of Issuance Costs Proceeds from exercise of stock options and warrants Proceeds From Stock Options Exercised Proceeds from Issuance of common stock in connection with IPO Proceeds From Issuance Of Common Stock Proceeds from issuance of common stock and restricted common stock Proceeds From Issuance Of Common And Restricted Stocks Repayment of notes payable Repayments Of Notes Payable Payments of initial public offering costs Payments For Repurchase Of Initial Public Offering 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 disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid Supplemental disclosure of non-cash investing and financing activities: Noncash Investing And Financing Items [Abstract] Accretion of convertible preferred stock to redemption value Issuance of preferred stock warrant in connection with notes payable Issuance Of Warrants In Connection With Notes Payable Deferred offering costs included in accounts payable Liabilities Assumed1 Property and equipment purchases included in accounts payable and accrued expenses Capital Expenditures Incurred But Not Yet Paid Accounting Policies [Abstract] Nature of the Business and Basis of Presentation Business Description And Basis Of Presentation [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value of Financial Assets and Liabilities Fair Value Disclosures [Text Block] Investments Debt And Equity Securities [Abstract] Investments Investments In Debt And Marketable Equity Securities And Certain Trading Assets Disclosure [Text Block] Property Plant And Equipment [Abstract] Property and Equipment, Net Property Plant And Equipment Disclosure [Text Block] Payables And Accruals [Abstract] Accrued Expenses and Other Current Liabilities Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Current [Text Block] Debt Disclosure [Abstract] Notes Payable Debt Disclosure [Text Block] Preferred stock warrants liability disclosure. Class Of Stock Disclosures [Abstract] Preferred Stock Warrant Liability Preferred Stock Warrants Liability Disclosure [Text Block] Equity [Abstract] Convertible Preferred Stock Preferred Stock [Text Block] Stockholders’ Equity (Deficit) Common Stock Shareholders Equity And Share Based Payments [Text Block] Earnings Per Share [Abstract] Net Loss per Share Earnings Per Share [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Quarterly Financial Data [Abstract] Selected Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Related Party Transactions [Abstract] Related Party Transactions Related Party Transactions Disclosure [Text Block] Compensation And Retirement Disclosure [Abstract] 401(k) Savings Plan Pension And Other Postretirement Benefits Disclosure [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Use of Estimates Use Of Estimates Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Restricted Cash Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Investments Investment Policy [Text Block] Concentration of Credit Risk and of Significant Suppliers Concentration Risk Credit Risk Fair Value Measurements Fair Value Measurement Policy Policy [Text Block] Deferred Offering Costs Deferred Charges 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] Research and Development Costs Research And Development Expense Policy Research contract costs and accruals policy. Research Contract Costs and Accruals Research Contract Costs And Accruals Policy [Text Block] Patent costs policy. Patent Costs Patent Costs Policy [Text Block] Accounting for Stock-Based Compensation Share Based Compensation Option And Incentive Plans Policy Income Taxes Income Tax Policy [Text Block] Warrants to purchase convertible preferred stock. Warrant to Purchase Convertible Preferred Stock Warrants To Purchase Convertible Preferred Stock Policy [Text Block] Segment Data Segment Reporting Policy Policy [Text Block] Comprehensive Loss Comprehensive Income Policy Policy [Text Block]