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 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 Deferred offering costs noncurrent. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Available for sale securities Available For Sale Securities Current 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 Deferred offering costs Deferred Offering Costs Noncurrent 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 expenses Accrued Liabilities Current Total current liabilities Liabilities Current Other liabilities Other Liabilities Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 8) Commitments And Contingencies Stockholders' equity: Stockholders Equity [Abstract] Preferred stock $0.00001 par value, 25,000,000 shares authorized at December 31, 2015 and 2014; 0 shares issued and outstanding at December 31, 2015 and 2014 Preferred Stock Value Common stock: $0.00001 par value; 175,000,000 shares authorized at December 31, 2015 and 2014; 30,662,218 and 20,370,624 shares issued and outstanding at December 31, 2015 and 2014, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Treasury stock, at cost, 8,463 shares Treasury Stock Value 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 issued Preferred Stock Shares Issued 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 Treasury Stock, shares Treasury Stock Shares 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 Operating loss Operating Income Loss Other income (expense): Nonoperating Income Expense [Abstract] Interest income (expense), net Interest Income Expense Net Extinguishment of debt and other liabilities Gains Losses On Extinguishment Of Debt Other income Other Nonoperating Income Net loss Net Income Loss Reconciliation of net loss to net loss applicable to common stockholders: Net Income Loss Available To Common Stockholders Basic [Abstract] Net loss Accretion on preferred stock Temporary Equity Accretion To Redemption Value Adjustment Net loss applicable to common stockholders Net Income Loss Available To Common Stockholders Basic Net loss per share applicable to common stockholders—basic and diluted Earnings Per Share Basic And Diluted Weighted-average number of common shares used in net loss per share applicable to common stockholders—basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Comprehensive loss: Comprehensive Income Net Of Tax [Abstract] Other comprehensive loss - unrealized loss on securities Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Comprehensive loss Comprehensive Income Net Of Tax Reclassifications of temporary to permanent equity shares Temporary equity stock issued during period shares new issues Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] Statement Class Of Stock Statement Class Of Stock [Axis] Class Of Stock Class Of Stock [Domain] Series A redeemable convertible preferred stock Series A Preferred Stock [Member] Series B redeemable convertible preferred stock Series B Preferred Stock [Member] Series C redeemable convertible preferred stock Series C Preferred Stock [Member] Two thousand twelve series X preferred stock. 2012 Series X Redeemable Convertible Preferred Stock Two Thousand Twelve Series X Preferred Stock [Member] Subsidiary Sale Of Stock Subsidiary Sale Of Stock [Axis] Sale Of Stock Name Of Transaction Sale Of Stock Name Of Transaction [Domain] IPO I P O [Member] 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] Treasury Stock Treasury Stock [Member] Unrealized Gain/Loss Accumulated Net Unrealized Investment Gain Loss [Member] Accumulated Deficit Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Balance Balance, shares Balance Temporary Equity Carrying Amount Attributable To Parent Balance, shares Temporary Equity Shares Outstanding Issuance of restricted common stock Stock Issued During Period Value Restricted Stock Award Gross Issuance of restricted common stock, shares Stock Issued During Period Shares Restricted Stock Award Gross Issuance of common stock, net of issuance costs Stock Issued During Period Value New Issues Issuance of common stock, net of issuance costs, shares Stock Issued During Period Shares New Issues Receipt of payment on promissory notes issued in exchange for shares of common stock Adjustments To Additional Paid In Capital Other Exercise of stock options, shares Stock Issued During Period Shares Stock Options Exercised Exercise of stock options Stock Issued During Period Value Stock Options Exercised Proceeds from sale of stock under employee stock purchase plan Stock Issued During Period Value Employee Stock Purchase Plan Proceeds from sale of stock under employee stock purchase plan, shares Stock Issued During Period Shares Employee Stock Purchase Plans Forfeitures of restricted common stock Stock Issued During Period Value Restricted Stock Award Forfeitures Forfeitures of restricted common stock, shares Stock Issued During Period Shares Restricted Stock Award Forfeited Reclassification of 2012 Series X preferred stock upon modification Reclassifications Of Temporary To Permanent Equity Reclassification of 2012 Series X preferred stock upon modification, shares Reclassifications Of Temporary To Permanent Equity Shares Sale of preferred stock, net of issuance cost Temporary Equity Stock Issued During Period Value New Issues Sale of preferred stock, net of issuance cost, shares Temporary Equity Stock Issued During Period Shares New Issues Conversion of preferred stock, shares Stock Issued During Period Shares Conversion Of Convertible Securities Conversion of preferred stock Stock Issued During Period Value Conversion Of Convertible Securities Accretion of preferred stock to redemption value Temporary Equity Accretion To Redemption Value Accretion of preferred stock to redemption value Preferred Stock Accretion Of Redemption Discount Share-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Deferred offering costs- IPO Adjustments To Additional Paid In Capital Stock Issued Issuance Costs Unrealized gain/loss Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Treasury shares purchased, not retired( 2,553) Treasury Stock Value Acquired Cost Method Treasury shares purchased, not retired in shares Treasury Stock Shares Acquired Treasury shares purchased, retired (5,910) Treasury Stock Retired Cost Method Amount Treasury shares purchased, retired in shares Treasury Stock Shares Retired Net income (loss) Balance Balance, shares Balance Balance, shares Series X preferred stock. Series X Preferred Stock Series X Preferred Stock [Member] Issuance cost Payments Of Stock Issuance Costs Proceeds from issuance of common stock net of issuance costs. Conversion of Preferred Stock into Common Stock. Deferred stock offering costs included in accounts payable and accrued liabilities. Deferred follow on offering issuance costs. Assets acquired under capital leases. Proceeds from reclassification of debt to preferred stock. 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] Gain on extinguishment of debt and other liabilities Depreciation expense Depreciation Amortization of debt issuance costs Amortization Of Financing Costs Amortization of premium/discount on investments Accretion Amortization Of Discounts And Premiums Investments Stock-based compensation expense Allocated Share Based Compensation 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 Other assets Increase Decrease In Other Operating Assets Accounts payable Increase Decrease In Accounts Payable Accrued expenses Increase Decrease In 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 Investing activities: Net Cash Provided By Used In Investing Activities Continuing Operations [Abstract] Purchase of equipment Payments To Acquire Property Plant And Equipment Proceeds from maturities of available for sale securities Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Purchases of available for sale securities Payments To Acquire Available For Sale Securities 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 the issuance of redeemable convertible preferred stock, net of issuance costs Proceeds From Issuance Of Redeemable Convertible Preferred Stock Proceeds from the issuance of 2012 Series X preferred stock, net of issuance costs Proceeds From Issuance Of Preferred Stock And Preference Stock Proceeds from the issuance of common stock, net of issuance costs Proceeds From Issuance Of Common Stock Net Of Issuance Costs Proceeds from sale of stock under employee stock purchase plan Proceeds From Stock Plans Proceeds from the exercise of stock options Proceeds From Stock Options Exercised Repurchase of treasury stock Payments For Repurchase Of Common Stock Payments received on promissory notes issued in exchange for shares of common stock Proceeds From Repayments Of Notes Payable Payments on capital lease obligations Repayments Of Long Term Capital Lease Obligations Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Increase in cash and cash equivalents Cash And Cash Equivalents Period Increase Decrease Cash and cash equivalents at beginning of period Cash and cash equivalents at end of period Non-cash financing activities: Noncash Investing And Financing Items [Abstract] Conversion of series A, series B and series C preferred stock into common stock Conversion Of Preferred Stock Into Common Stock Accretion of preferred stock to redemption value Unpaid initial public offering issuance costs Deferred Stock Offering Costs Included In Accounts Payable And Accrued Liabilities Unpaid follow-on offering costs Deferred Follow On Offering Issuance Costs Assets acquired under capital lease Assets Acquired Under Capital Leases Reclassification of 2012 Series X preferred stock from debt to preferred stock Proceeds From Reclassification Of Debt To Preferred Stock Conversion of 2012 Series X preferred stock into Series C preferred stock Convertible Preferred Stock Converted To Other Securities Accounting Policies [Abstract] Nature of Organization and Operations Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Investments Debt And Equity Securities [Abstract] Available for Sale Securities Investments In Debt And Marketable Equity Securities And Certain Trading Assets Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value of Financial Instruments Fair Value Disclosures [Text Block] Payables And Accruals [Abstract] Accrued Expenses Accounts Payable And Accrued Liabilities Disclosure [Text Block] Equity [Abstract] Stockholders' Equity Stockholders Equity Note Disclosure [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] Compensation And Retirement Disclosure [Abstract] Employee Retirement Plan Pension And Other Postretirement Benefits Disclosure [Text Block] Earnings Per Share [Abstract] Net Loss per Share Earnings Per Share [Text Block] Quarterly Financial Information Disclosure [Abstract] Quarterly Results (unaudited) Quarterly Financial Information [Text Block] Subsequent Events [Abstract] Subsequent Event Subsequent Events [Text Block] Basis of Presentation Basis Of Accounting Policy Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Segment Information Segment Reporting Policy 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] Patents Intangible Assets Finite Lived Policy Income Taxes Income Tax Policy [Text Block] Stock-Based Compensation Share Based Compensation Option And Incentive Plans Policy Fair Value of Financial Instruments Fair Value Of Financial Instruments Policy Concentrations of Credit Risk and Off-Balance Sheet Risk Concentration Risk Credit Risk Net Loss per Share Earnings Per Share Policy [Text Block] Property and Equipment Property Plant And Equipment Policy [Text Block] Summary of Equipment and Related Accumulated Depreciation Property Plant And Equipment [Text Block]