Document and Entity Information 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 Current Reporting Status Entity Filer Category Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Condensed Consolidated Balance Sheets Assets Abstract Assets Assets, Current Abstract Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Marketable Securities, Current Marketable securities, current Prepaid expenses and other current assets Assets, Current Total current assets Property and equipment, net Deposits and other assets that are expected to be realized or consumed after one year. Deposits And Other Assets Non-Current Deposits and other non-current assets Marketable Securities, Noncurrent Marketable securities, non-current Assets Total assets Liabilities and Equity Abstract Liabilities and stockholders’ equity Liabilities, Current Abstract Current liabilities: Accounts payable Accrued Liabilities, Current Accrued expenses Total Contract with Customer, Liability, Current Deferred revenue, current Liabilities, Current Total current liabilities Deferred Rent Credit, Noncurrent Deferred rent Contract with Customer, Liability, Noncurrent Deferred revenue, non-current Other non-current liabilities Liabilities Total liabilities Commitments and contingencies (see note 6) Stockholders' Equity Attributable to Parent Abstract Stockholders’ equity: Preferred stock $0.001 par value: 5,000,000 shares authorized at March 31, 2018 and December 31, 2017; no shares issued and outstanding at March 31, 2018 and December 31, 2017 Common stock, $0.001 par value: 120,000,000 shares authorized at March 31, 2018 and December 31, 2017; 31,888,998 and 31,572,044 shares issued and outstanding at March 31, 2018 and December 31, 2017, respectively 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 Total stockholders’ equity Liabilities and Equity Total liabilities and stockholders’ equity Preferred Stock, Par or Stated Value Per Share Preferred Stock, par value (in dollars per share) Preferred Stock, Shares Authorized Preferred stock, authorized Preferred Stock, Shares Issued Preferred Stock, Shares Outstanding Common Stock, Par or Stated Value Per Share Common stock, par value (in dollars per share) Common Stock, Shares Authorized Common Stock, Shares, Issued Common Stock, Shares, Outstanding Condensed Consolidated Statements of Operations and Comprehensive Loss Revenues Collaboration revenue Operating expenses: Research and development expense Research and development General and Administrative Expense General and administrative Operating Expenses Total operating expenses Operating Income (Loss) Operating loss Interest and Debt Expense [Abstract] Other income: Interest income Other financing expense Other income Interest and Debt Expense Total other income Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Loss before income taxes Loss from operations Income Tax Expense (Benefit) Income tax benefit Net Income (Loss) Attributable to Parent Net loss Net loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Other comprehensive income Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Net unrealized gain on available-for-sale-securities, net of tax expense of $244 for the three months ended March 31, 2017 Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total other comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Earnings Per Share, Basic and Diluted Net loss per share, basic and diluted Weighted average number of common shares outstanding, basic and diluted (in shares) Weighted-average common shares outstanding, basic and diluted Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Tax Tax expense Tax expense recognized in OCI Condensed Consolidated Statement of Cash Flows Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Cash flow from operating activities Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Adjustments to reconcile net loss to net cash provided by operating activities: Adjustments to reconcile net loss to net cash provided by (used in) operating activities: Stock-based compensation expense Depreciation Accretion (Amortization) of Discounts and Premiums, Investments Amortization of premiums and discounts on marketable securities In-kind research and development expenses. In-kind research and development expenses Other Noncash Income (Expense) Other non-cash items Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets Increase (Decrease) in Other Noncurrent Assets Other non-current assets Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration has been received or is receivable. Increase (Decrease) in Contract with Customer, Liability Deferred revenue Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses Increase (Decrease) in Other Noncurrent Liabilities Other non-current liabilities The increase (decrease) in deferred lease incentive credit from lessor. Increase Decrease In Deferred Lease Incentive Credit From Lessor Lease incentive benefit Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash provided by (used in) operating activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Cash flow from investing activities Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Payments to Acquire Marketable Securities Purchases of marketable securities Proceeds from Sale and Maturity of Marketable Securities Proceeds from maturities of marketable securities Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash provided by investing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Cash flow from financing activities Proceeds from Stock Options Exercised Proceeds from the exercise of stock options Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Excluding Stock Options Proceeds from the purchase of common stock under ESPP Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash provided by financing activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net increase in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents, and restricted cash end of period Cash, cash equivalents, and restricted cash beginning of period Total cash, cash equivalents, and restricted cash Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosure of cash and non-cash activities Capital Expenditures Incurred but Not yet Paid Capital expenditures incurred but not yet paid New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification Impact of adopting new accounting standards Nature of business Nature of Operations [Text Block] Nature of business Summary of significant accounting policies Significant Accounting Policies [Text Block] Summary of significant accounting policies Fair value measurements Fair Value Disclosures [Text Block] Fair value measurements Cash, cash equivalents, restricted cash, and available for sale marketable securities Schedule of Cash and Cash Equivalents [Table] Cash and Cash Equivalents [Line Items] Cash, cash equivalents, and restricted cash Cash and Cash Equivalents Disclosure [Text Block] Cash, cash equivalents, restricted cash, and available for sale marketable securities Accrued expenses n/a Accrued Liabilities Disclosure [Text Block] Accrued expenses Commitments and contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and contingencies Redeemable convertible preferred stock n/a Redeemable Convertible Preferred Stock Disclosure [Text Block] Redeemable convertible preferred stock Stock based compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock based compensation Income taxes Income Tax Disclosure [Text Block] Income taxes Net loss per share Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Earnings Per Share [Text Block] Net loss per share Related party transactions Related Party Transactions Disclosure [Text Block] Related party transactions Basis of presentation Consolidation, Policy [Policy Text Block] Principles of consolidation Use of estimates Disclosure of accounting policy for revenue from contract with customer. Revenue from Contract with Customer [Policy Text Block] Revenue Recognition Recent accounting pronouncements New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of impact of adoption of financial statement line items shows comparative balances under ASC 606 and ASC 605 Assets and liabilities measured at fair value on a recurring basis Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table Text Block] Summary of fair value assumptions Cash, cash equivalents and marketable securities Tabular disclosure of the components of cash, cash equivalents, and restricted cash. Schedule of Cash Cash Equivalents And Restricted Cash [Table Text Block] Reconciliation of cash, cash equivalents, and restricted cash Schedule of accrued expenses Summary of contractual obligations as of payment due date Allocable arrangement consideration allocation Tabular disclosure of revenue performance obligation allocation of transaction price. Revenue Performance Obligation Allocation of Transaction Price [Table Text Block] Schedule of allocation of transaction price Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Compensation cost recognized for all stock-based compensation awards Summary of status and changes in unvested restricted stock Summary of status and changes in stock options Assumptions Outstanding potentially dilutive securities excluded in the calculation of diluted net loss per share The cash inflow from the issuance of common stock, preferred stock, treasury stock, stock options, and other types of equity as well as Collaboration Agreements. Proceeds From Issuance Of Equity And Collaboration Agreements Proceeds raised Cash, Cash Equivalents, and Short-term Investments Cash, cash equivalent, and available-for-sale securities Represents the number of open contracts the entity has currently. Number Of Open Contracts Number of open contracts Revenue from Contract with Customer, Excluding Assessed Tax Collaboration revenue Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Assets, Fair Value Disclosure [Abstract] Assets, Fair Value Disclosure [Abstract] Cash and cash equivalents Investments Financial Instruments, Owned, Corporate Equities, at Fair Value Warrants to purchase equity securities Assets, Fair Value Disclosure, Total Total assets measured at fair value Fair value assumptions Fair Value Assumptions, Risk Free Interest Rate Risk-free interest rate Fair Value Assumptions, Expected Term Expected term (in years) Fair Value Assumptions, Expected Volatility Rate Expected volatility Amortized Cost Basis [Abstract] Amortized Cost Available-for-sale Debt Securities, Amortized Cost Basis Marketable securities, amortized cost Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value. Equity Securities, FV-NI, Cost Marketable equity securities, amortized cost Cost of investment in debt investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value. Debt Securities Trading and Equity Securities, FV-NI Cost Total marketable securities, amortized cost Represents the value of money market funds and marketable securities on amortized cost basis. Money Market Funds And Marketable Securities, Amortized Cost Basis Total money market funds and marketable securities Fair Value Disclosure [Abstract] Fair Value Available-for-sale Securities, Debt Securities Marketable debt securities, fair value Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Equity Securities, FV-NI Marketable equity securities, fair value Trading Securities Total marketable securities Represents the fair value of money market funds and marketable securities. Money Market Funds And Marketable Securities Fair Value Total money market funds and marketable securities n/a Unrealized Gain and Loss [Abstract] Unrealized Gains and Losses Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Equity Securities, FV-NI, Unrealized Gain Equity securitiess, unrealized gains This item represents equity securities and available for sale debt securities gross unrealized gains. Equity Securities And Available For Sale Debt Securities Gross Unrealized Gains Total marketable securities, unrealized gains Represents the unrealized gain before tax on money market funds and marketable securities gross . Money Market Funds And Marketable Securities Gross Unrealized Gain Before Tax Total money market funds and marketable securities Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Marketable securities, unrealized losses Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Equity Securities, FV-NI, Unrealized Loss Equity securitiess, unrealized losses This item represents equity securities and available for sale debt securities gross unrealized losses. Equity Securities And Available For Sale Debt Securities Gross Unrealized Losses Total marketable securities, unrealized losses Represents the gross unrealized loss before tax from money market funds and marketable securities. Money Market Funds And Marketable Securities Gross Unrealized Loss Before Tax Total money market funds and marketable securities Restricted Cash Restricted cash included in deposits and other noncurrent assets Carrying value as of the balance sheet date of obligations incurred through that date and payable for research and development costs . Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Research And Development Costs Current Research and development costs Professional services Employee compensation costs Represents the amount of expenses incurred but not paid for goods and services, due within one year or the normal operating cycle, if longer. Accrued Goods And Services Current Accrued goods and services Carrying value as of the balance sheet date of obligations incurred through that date and payable for patent costs. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Patent Costs Current Patent costs Other The number of renewal options available to the reporting entity based upon the operating lease agreement. Operating Leases Number Of Renewal Options Number of renewal options Leasehold Improvements, Gross Leasehold improvement receivable Term of each renewal option