This concept does not have a custom type definition. Document and Entity Information [Abstract] Statement [Table] Statement [Line Items] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Public Float Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Statement of Financial Position [Abstract] Assets [Abstract] Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and cash equivalents Available-for-sale Securities, Debt Securities, Current Investments, available-for-sale Represents the current amount of unbilled accounts receivable, including reimbursable research and development costs. Unbilled Receivables Including Reimbursable Costs Current Unbilled accounts receivable Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Assets, Current Total current assets Available-for-sale Securities, Debt Securities, Noncurrent Investments, available-for-sale Property, Plant and Equipment, Net Property and equipment, net Total property and equipment, net Restricted Cash and Cash Equivalents, Noncurrent Restricted cash Restricted cash included in long-term assets Other Assets, Noncurrent Other assets Assets Total assets Liabilities and Equity [Abstract] Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Total accrued expenses Deferred Revenue, Current Current portion of deferred revenue Lease Incentive, Payable, Current Current portion of lease incentive obligation Loans Payable to Bank, Current Current portion of term loan payable Liabilities, Current Total current liabilities Deferred Rent Credit, Noncurrent Deferred rent, net of current portion Deferred Revenue, Noncurrent Deferred revenue, net of current portion This item represents an incentive or inducement contractually stipulated between parties to a lease whereby the lessor has committed to provide the entity (lessee) with a cash payment as inducement to enter the lease. Used to reflect the noncurrent portion of the liabilities. Lease Incentive Payable Noncurrent Lease incentive obligation, net of current portion Loans Payable to Bank, Noncurrent Term loan payable, net of current portion Other Liabilities, Noncurrent Other long term liabilities Commitments and Contingencies Commitments (Note 10) Stockholders' Equity Attributable to Parent [Abstract] Stockholders’ equity: Preferred Stock, Value, Outstanding Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued and outstanding Common Stock, Value, Issued Common stock, $0.001 par value; 120,000,000 shares authorized; 43,577,526 and 33,125,479 shares issued at December 31, 2017 and December 31, 2016, respectively; 43,577,526 and 33,123,354 shares outstanding at December 31, 2017 and December 31, 2016, respectively Additional Paid in Capital Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Retained Earnings (Accumulated Deficit) Accumulated deficit Stockholders' Equity Attributable to Parent Ending Balance Beginning Balance Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Preferred Stock Disclosures Preferred Stock, Par or Stated Value Per Share Preferred stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, shares authorized (in shares) Preferred Stock, Shares Issued Preferred stock, shares issued (in shares) Preferred Stock, Shares Outstanding Preferred stock, shares outstanding (in shares) Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Common Stock Disclosures Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common stock, shares authorized (in shares) Common Stock, Shares, Issued Ending Balance (in shares) Beginning Balance (in shares) Common stock, shares issued (in shares) Common Stock, Shares, Outstanding Common Stock, shares outstanding (in shares) Income Statement [Abstract] Revenues [Abstract] Revenues Revenues Collaboration revenue Total revenue Operating Expenses [Abstract] Operating expenses: Research and Development Expense Research and development General and Administrative Expense General and administrative Operating Expenses Total operating expenses Total operating expenses Nonoperating Income (Expense) [Abstract] Other income (expense): Other Nonoperating Income (Expense) Other income (expense), net Interest and Debt Expense Interest expense Nonoperating Income (Expense) Total other income (expense), net Total other income (expense) Net Income (Loss) Attributable to Parent Net loss Net loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive loss: Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Unrealized loss on investments Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Reconciliation of net loss applicable to common stockholders: Temporary Equity, Dividends, Adjustment Convertible preferred stock dividends Net Income (Loss) Available to Common Stockholders, Basic Net loss applicable to common stockholders Income (Loss) from Continuing Operations, Per Basic and Diluted Share Net loss per share applicable to common stockholders - basic and diluted (in dollars per share) Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted Statement of Stockholders' Equity [Abstract] Class of Stock [Axis] Class Of Stock [Domain] Class of Stock [Domain] Series A Preferred Stock [Member] Series A convertible preferred stock Series B Preferred Stock [Member] Series B convertible preferred stock Series C Preferred Stock [Member] Series C convertible preferred stock Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Common Stock [Member] Common Stock Additional Paid In Capital [Member] Additional Paid-In Capital Accumulated Other Comprehensive Income [Member] Accumulated Other Comprehensive (Loss) Income Retained Earnings [Member] Accumulated Deficit Increase (Decrease) in Temporary Equity [Roll Forward] Increase (Decrease) in Convertible Preferred Stock Temporary Equity, Carrying Amount, Attributable to Parent Ending Balance Beginning Balance Temporary Equity, Shares Issued Ending Balance (in shares) Beginning Balance (in shares Represents the value of temporary equity stock converted during the period. Temporary Equity Stock Value Converted Conversion of preferred stock into common stock Represents the number of temporary equity shares converted during the period. Temporary Equity Stock Shares Converted Conversion of preferred stock into common stock (in shares) Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity Stock Issued During Period, Value, Conversion of Convertible Securities Conversion of preferred stock into common stock Stock Issued During Period, Shares, Conversion of Convertible Securities Stock issued upon exercise of warrants Conversion of preferred stock into common stock (in shares) Stock Issued During Period, Value, New Issues Initial public offering / Follow on offering, net of issuance costs Stock Issued During Period, Shares, New Issues Stock sold (in shares) Initial public offering / Follow on offering, net of issuance costs (in shares) Adjustments to Additional Paid in Capital, Warrant Issued Reclassification of warrant Value of stock issued as a result of the exercise of warrants. Stock Issued During Period Value Warrants Exercised Issuance of common stock upon warrant exercise Number of share warrants (or share units) exercised during the current period. Stock Issued During Period Shares Warrants Exercised Issuance of common stock upon warrant exercise (in shares) Stock Issued During Period, Value, Share-based Compensation, Net of Forfeitures Issuance of common stock under stock plan Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures Issuance of common stock under stock plan (in shares) Stock Issued During Period, Value, Employee Stock Purchase Plan Purchase of common stock under ESPP Stock Issued During Period, Shares, Employee Stock Purchase Plans ESPP shares issued during period Purchase of common stock under ESPP (in shares) Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation expense Available-for-sale Securities, Gross Unrealized Gain (Loss) Unrealized loss on available-for-sale securities, net of tax Statement of Cash Flows [Abstract] Net Cash Provided by (Used in) Operating Activities [Abstract] Operating activities Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Depreciation, Depletion and Amortization Depreciation and amortization Amortization of Debt Issuance Costs Noncash interest expense Fair Value Adjustment of Warrants Change in fair value of warrant liability Share-based Compensation Stock-based compensation The cash inflow from the accretion of premiums and discounts on investments. Accretion Of Premiums And Discounts On Investments Accretion of premiums and discounts on investments Increase (Decrease) in Operating Capital [Abstract] Changes in assets and liabilities: Increase (Decrease) in Unbilled Receivables Unbilled accounts receivable Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets Increase (Decrease) in Other Noncurrent Assets Other assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses Increase (Decrease) in Deferred Revenue Deferred revenue Amount of increase (decrease) in deferred rent. Increase Decrease In Deferred Rent Deferred rent Net Cash Provided by (Used in) Operating Activities Net cash used in operating activities Net Cash Provided by (Used in) Investing Activities [Abstract] Investing activities Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Increase (Decrease) in Restricted Cash Restricted cash Payments to Acquire Available-for-sale Securities, Debt Purchases of investments Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities Maturities of investments Net Cash Provided by (Used in) Investing Activities Net cash used in investing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Financing activities Repayments of Bank Debt Principal payments on loan payable Payments of Stock Issuance Costs Payment of offering costs Proceeds from Issuance Initial Public Offering Proceeds from issuance of IPO shares Proceeds from public offering of common stock, net of commissions and underwriting discounts Proceeds from Issuance of Common Stock Proceeds from issuance of common stock, net of repurchases Proceeds from issuance of common stock Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Cash and Cash Equivalents, Period Increase (Decrease) Net increase (decrease) in cash and cash equivalents Supplemental Cash Flow Information [Abstract] Supplemental cash flow information Represents the future cash outflow to pay stock issuance costs that have occurred in a noncash or partial noncash transaction. Stock Issuance Costs Incurred but Not yet Paid Noncash Or Partial Noncash Transaction Public offering costs incurred but unpaid at period end Capital Expenditures Incurred but Not yet Paid Property and equipment purchases unpaid at period end Conversion of Stock, Amount Converted Conversion of convertible preferred stock into common stock The value of warrant liability that was reclassified to additional paid-in-capital. Reclassification of Warrant Liability to Additional Paid In Capital Reclassification of warrant liability to additional paid-in-capital Interest Paid, Net Cash paid for interest Organization, Consolidation and Presentation of Financial Statements [Abstract] Disclosure Text Block [Abstract] Disclosure Text Block Nature of Operations [Text Block] Nature of Business Accounting Policies [Abstract] Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies and Recent Accounting Pronouncements Investments and Cash [Abstract] Cash, Cash Equivalents, and Marketable Securities [Text Block] Cash Equivalents and Investments Fair Value Disclosures [Abstract] Fair Value Disclosures [Text Block] Fair Value of Financial Instruments Restricted Cash and Investments [Abstract] Restricted Assets Disclosure [Text Block] Restricted Cash Property, Plant and Equipment [Abstract] Property, Plant and Equipment Disclosure [Text Block] Property and Equipment, Net Payables and Accruals [Abstract] Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accrued Expenses Collaborative Arrangement Disclosure [Abstract] Collaborative Arrangement Disclosure [Abstract] Collaborative Arrangement Disclosure [Text Block] Collaborations Debt Disclosure [Abstract] Long-term Debt [Text Block] Term Loan Warrants and Rights Note Disclosure [Abstract] The entire disclosure for warrants. Warrants Disclosure [Text Block] Warrants Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock Awards Earnings Per Share [Abstract] Earnings Per Share [Text Block] Net Loss per Share Stockholders' Equity Note [Abstract] Stockholders' Equity Note Disclosure [Text Block] Convertible Preferred Stock Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Taxes Commitments and Contingencies Disclosure [Abstract] Commitments Disclosure [Text Block] Commitments Retirement Benefits [Abstract] Pension and Other Postretirement Benefits Disclosure [Text Block] Defined Contribution Benefit Plan Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information [Text Block] Selected Quarterly Financial Data (unaudited) Subsequent Events [Abstract] Subsequent Events [Text Block] Subsequent Event Policy Text Block [Abstract] Policy Text Blocks Basis of Accounting, Policy [Policy Text Block] Basis of Presentation Use of Estimates, Policy [Policy Text Block] Use of Estimates Disclosure of significant accounting policies. Significant Accounting Policy [Policy Text Block] Significant Accounting Policies Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block] Available-for-sale Investments Revenue Recognition, Policy [Policy Text Block] Revenue recognition Comprehensive Income, Policy [Policy Text Block] Comprehensive Income (Loss) Research and Development Expense, Policy [Policy Text Block] Research and Development Costs Property, Plant and Equipment, Policy [Policy Text Block] Property and Equipment, Net Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment of Long Lived Assets