Entity Central Index Key Debt instrument current portion of long term gross. Debt instrument accrual of final payment. 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 Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Shell Company Entity Shell Company 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 Available-for-sale investments, short-term Available For Sale Securities Debt Securities Current Prepaid expenses and other assets Prepaid Expense And Other Assets Current Total current assets Assets Current Property and equipment, net Property Plant And Equipment Net 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 Current portion of long-term debt, net of issuance costs and discount Long Term Debt Current Total current liabilities Liabilities Current Long-term debt, net of current portion and issuance costs and discount Long Term Debt Noncurrent Commitments and contingencies (Note 5) Commitments And Contingencies Stockholders’ equity: Stockholders Equity [Abstract] Preferred stock, $0.001 par value; undesignated authorized shares – 5,000,000 at December 31, 2018 and 2017, respectively; Class X Convertible Preferred Stock issued and outstanding shares – 2,285,952 as of December 31, 2018 and 2017, respectively Preferred Stock Value Common stock, $0.001 par value; authorized shares – 150,000,000 as of December 31, 2018 and 2017, respectively; issued and outstanding shares – 30,579,076 and 29,789,162 as of December 31, 2018 and 2017, respectively 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 Statement [Table] Statement [Table] Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Class X convertible preferred stock. Class X Convertible Preferred Stock [Member] Class X Convertible Preferred Stock [Member] Statement [Line Items] Statement [Line Items] 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 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] Other income (expense), net Other Nonoperating Income Expense Loss on extinguishment of debt Gains Losses On Extinguishment Of Debt Total other income (expense), net Nonoperating Income Expense Loss before income taxes Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Income tax benefit Income Tax Expense Benefit Net loss Net Income Loss Net loss per share attributable to common stock holders, basic and diluted Earnings Per Share Basic And Diluted Weighted average common stock shares outstanding, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Net loss Other comprehensive gain (loss): Other Comprehensive Income Loss Net Of Tax Period Increase Decrease [Abstract] Change in unrealized gain (loss) on available for sale investments, net of tax Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Comprehensive loss Comprehensive Income Net Of Tax Stock issued during period, value, stock options exercised and release of restricted stock units. Stock issued during period, shares, stock options exercised and release of restricted stock units. Increase (decrease) to additional paid in capital changes to share repurchase liability. Stock issued during period shares private placement net of offering costs. Stock issued during period value private placement net of offering costs. Stock issued during period value at the market offerings net of offering costs. Stock issued during period shares at the market offerings net of offering costs. Statement Of Stockholders Equity [Abstract] Convertible Preferred Stock [Member] Convertible Preferred Stock [Member] 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] Other Comprehensive Loss [Member] Accumulated Other Comprehensive Income [Member] Accumulated Deficit [Member] Retained Earnings [Member] Beginning balance Beginning balance, Shares Shares Outstanding Exercise of common stock options and release of restricted stock units Stock Issued During Period Value Stock Options Exercised And Release Of Restricted Stock Units Exercise of common stock options and release of restricted stock units, Shares Stock Issued During Period Shares Stock Options Exercised And Release Of Restricted Stock Units Issuance of common stock pursuant to employee stock purchase plan Stock Issued During Period Value Employee Stock Purchase Plan Issuance of common stock pursuant to employee stock purchase plan, Shares Stock Issued During Period Shares Employee Stock Purchase Plans Issuance of common stock from at the market offerings, net of offering costs Stock Issued During Period Value At The Market Offerings Net Of Offering Costs Issuance of common stock from at the market offerings, net of offering costs, Shares Stock Issued During Period Shares At The Market Offerings Net Of Offering Costs Issuance of common stock and preferred stock from private placement, net of offering costs Stock Issued During Period Value Private Placement Net Of Offering Costs Issuance of common stock and preferred stock from private placement, net of offering costs, Shares Stock Issued During Period Shares Private Placement Net Of Offering Costs Issuance of warrants related to term loan Adjustments To Additional Paid In Capital Warrant Issued Changes in share repurchase liability Increase Decrease To Additional Paid In Capital Changes To Share Repurchase Liability Stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Net unrealized gain (loss) on investments, net of tax Ending balance Ending balance, Shares This element represents the change during the reporting period in the carrying value for deferred rent. Proceeds from issuance of common stock through at market offering net of offering costs. Purchases of fixed assets included in accounts payable. Issuance of warrants in connection with borrowings. Statement Of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities [Abstract] Net loss Profit Loss 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 Stock-based compensation Allocated Share Based Compensation Expense Debt discount accretion and non-cash interest expense Accretion Expense Loss on debt extinguishment Amortization (accretion) of premium (discount) of available-for-sale investment securities Accretion Amortization Of Discounts And Premiums Investments Loss on disposal of property and equipment Gain Loss On Sale Of Property Plant Equipment Deferred rent Increase Decrease In Deferred Rent Credit Changes in operating assets and liabilities Increase Decrease In Operating Capital [Abstract] Prepaid expenses and other assets Increase Decrease In Prepaid Deferred Expense And Other Assets Accounts payable and accrued expenses Increase Decrease In Accounts Payable And Accrued Liabilities Net cash used in operating activities Net Cash Provided By Used In Operating Activities Cash flows from investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Purchases of property and equipment Payments To Acquire Property Plant And Equipment Purchases of available-for-sale investment securities Payments To Acquire Available For Sale Securities Debt Maturities of available-for-sale investment securities Proceeds From Sale And Maturity Of Available For Sale Securities Net cash provided by (used in) investing activities Net Cash Provided By Used In Investing Activities Cash flows from financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Proceeds from issuance of common stock through option exercises Proceeds From Issuance Of Common Stock Proceeds from issuance of common stock through at the market offerings, net of offering costs Proceeds From Issuance Of Common Stock Through At Market Offering Net Of Offering Costs Proceeds from issuance of common stock through employee purchase plan Proceeds From Stock Plans Proceeds from borrowing, net Proceeds From Repayments Of Debt Repayment on borrowing Repayments Of Debt Proceeds from issuance of securities in the Private Placement, net of issuance cost Proceeds From Issuance Of Private Placement Net cash (used in) provided by financing activities Net Cash Provided By Used In Financing Activities Net change 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 the end of period Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Interest paid Interest Paid Net Purchase of fixed assets included in accounts payable Purchases Of Fixed Assets Included In Accounts Payable Supplemental schedule of noncash investing and financing activities: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Issuance of warrants in connection with borrowings Issuance Of Warrants In Connection With Borrowings Accounting Policies [Abstract] Organization, Business and Basis of Presentation Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Balance sheet details. Balance Sheet Details [Abstract] Balance Sheet Details Supplemental Balance Sheet Disclosures [Text Block] Debt commitments and contingencies. Debt Instruments [Abstract] Debt, Commitments and Contingencies Debt Commitments And Contingencies [Text Block] Equity [Abstract] Stockholders' Equity Shareholders Equity And Share Based Payments [Text Block] Income Tax Disclosure [Abstract] Income Tax Income Tax Disclosure [Text Block] Compensation And Retirement Disclosure [Abstract] Employee Benefits Compensation And Employee Benefit Plans [Text Block] Quarterly Financial Data [Abstract] Quarterly Financial Data (Unaudited) Quarterly Financial Information [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Organization and Business Basis Of Accounting Policy Policy [Text Block] Principles of Consolidation Consolidation Policy [Text Block] Use of Estimates Use Of Estimates Segment Reporting Segment Reporting Policy Policy [Text Block] Reclassifications Prior Period Reclassification Adjustment Description Cash and Cash Equivalents Cash And Cash Equivalents Policy [Text Block] Investment Securities Investment Policy [Text Block] Concentration of Credit Risk Concentration Risk Credit Risk 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] accrued expenses. Accrued Expenses Accrued Expenses Policy [Text Block] Research and Development Costs Research And Development Expense Policy Patent Costs Legal Costs Policy [Text Block] Stock-Based Compensation Compensation Related Costs Policy [Text Block] Income Taxes Income Tax Policy [Text Block] Net Loss Per Share Earnings Per Share Policy [Text Block] Convertible Preferred Stock Stockholders Equity Note Redeemable Preferred Stock Issue Policy Derivative Financial Instruments Derivatives Policy [Text Block] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Schedule of Potentially Dilutive Securities Not Included in Calculation of Diluted Net Loss Per Share Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Summary of Net Loss Per Share Schedule Of Earnings Per Share Basic And Diluted Table [Text Block] Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Schedule of Available-for-sale Investments Debt Securities Available For Sale Table [Text Block] Summary of Property and Equipment Property Plant And Equipment [Text Block] Summary of Accrued Expenses Schedule Of Accrued Liabilities Table [Text Block] Schedule of Term Loans and Unamortized Discount Balances Schedule Of Debt Instruments [Text Block] Schedule of Future Principal Payments for Term Loans Schedule Of Maturities Of Long Term Debt Table [Text Block] Schedule of Future Minimum Payments under Non-cancelable Operating Lease Schedule Of Future Minimum Rental Payments For Operating Leases Table [Text Block] Award Type Award Type [Axis] Equity Award Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Employee Stock Option [Member] Employee Stock Option [Member] Summary of Stock Option Activity Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Summary of Assumptions Used to Determine Fair Value of Employee Stock Option Grants and Performance Options with Market Condition Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Summary of Assumptions Used to Determine Fair Value of Employee Stock Purchase Plan Schedule Of Share Based Payment Award Employee Stock Purchase Plan Valuation Assumptions Table [Text Block] Schedule of Restricted Stock Units Activity Schedule Of Share Based Compensation Restricted Stock Units Award Activity Table [Text Block] Schedule of Allocation of Stock-Based Compensation for All Options Including Performance Options with Market Condition and Restricted Stock Units Schedule Of Compensation Cost For Share Based Payment Arrangements Allocation Of Share Based Compensation Costs By Plan Table [Text Block] Summary of Warrants Outstanding Schedule Of Stockholders Equity Note Warrants Or Rights [Text Block] Schedule of common stock reserved for future issuance. Summary of Common Stock Reserved for Future Issuance Schedule Of Common Stock Reserved For Future Issuance Table [Text Block] Schedule of Pretax Earnings (Loss) for Domestic and Foreign Operations Schedule Of Income Before Income Tax Domestic And Foreign Table [Text Block] Schedule of Reconciliations of the Expected Statutory Federal Income Tax Schedule Of Effective Income Tax Rate Reconciliation Table [Text Block] Schedule of Significant Components of Deferred Tax Assets Schedule Of Deferred Tax Assets And Liabilities Table [Text Block] Schedule of Activity Related to Unrecognized Tax Benefits Schedule Of Unrecognized Tax Benefits Roll Forward Table [Text Block] Summary of Quarterly Financial Data Schedule Of Quarterly Financial Information Table [Text Block]