Entity Central Index Key Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Accumulated Other Comprehensive Income Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable And Accrued Expenses Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Net Less Transaction Costs 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 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 Statement Of Financial Position [Abstract] Statement [Table] Statement [Table] Preferred Units by Name Preferred Units By Name [Axis] Preferred Units, Class Preferred Units Class [Domain] Contingently redeemable class A preferred units. Contingently Redeemable Class A Preferred Units Contingently Redeemable Class A Preferred Units [Member] Class B preferred units. Class B Preferred Units Class B Preferred Units [Member] Class A preferred units. Class A Preferred Units Class A Preferred Units [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 Short-term marketable 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 Restricted cash Restricted Cash Noncurrent Other assets Other Assets Noncurrent Total assets Assets Liabilities, Contingently Redeemable Preferred Equity and Stockholders' Equity Liabilities And Stockholders Equity [Abstract] Current liabilities: Liabilities Current [Abstract] Accounts payable Accounts Payable Current Accrued expenses Accrued Liabilities Current Deferred revenue Deferred Revenue Current Deferred rent Deferred Rent Credit Current Capital lease obligations Capital Lease Obligations Current Total current liabilities Liabilities Current Long-term liabilities: Liabilities Noncurrent [Abstract] Deferred revenue, net of current portion Deferred Revenue Noncurrent Deferred rent, net of current portion Deferred Rent Credit Noncurrent Capital lease obligations, net of current portion Capital Lease Obligations Noncurrent Total long-term liabilities Liabilities Noncurrent Commitments and contingencies (Note 18) Commitments And Contingencies Preferred units, value Temporary Equity Carrying Amount Attributable To Parent Preferred units, Units Issued Temporary Equity Shares Issued Preferred units, Units Outstanding Temporary Equity Shares Outstanding Stockholders' Equity Stockholders Equity [Abstract] Preferred stock, $0.001 par value 5,000,000 shares authorized, none issued and outstanding as of December 31, 2017 and December 31, 2016 Preferred Stock Value Preferred units, value Limited Liability Company L L C Preferred Unit Issuance Value Common stock, $0.001 par value 250,000,000 and 0 shares authorized as of December 31, 2017 and December 31, 2016. 16,272,617 shares issued and outstanding as of December 31, 2017 and 0 shares issued and outstanding as of December 31, 2016 Common Stock Value Common units Issued and outstanding 0 and 1,847,615 units as of December 31, 2017 and December 31, 2016, respectively Common Unit Issuance Value Additional paid-in capital Additional Paid In Capital Accumulated other comprehensive income Accumulated Other Comprehensive Income Loss Net Of Tax Accumulated deficit Retained Earnings Accumulated Deficit Total contingently redeemable preferred equity and stockholders' equity Stockholders Equity Total liabilities, contingently redeemable preferred equity 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 Preferred units, Units Issued Limited Liability Company L L C Preferred Unit Issued Preferred units, Units Outstanding Limited Liability Company L L C Preferred Unit Outstanding Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, authorized Common Stock Shares Authorized Common stock, Issued Common Stock Shares Issued Common stock, outstanding Common Stock Shares Outstanding Common units, Issued Common Unit Issued Common units, outstanding Common Unit Outstanding Income Statement [Abstract] Revenue Revenues 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): Nonoperating Income Expense [Abstract] Interest and investment income Investment Income Nonoperating Interest expense Interest Expense Other income (expense), net Nonoperating Income Expense Net loss Net Income Loss Net loss per share attributable to common shareholders - basic and diluted Earnings Per Share Basic And Diluted Weighted-average common shares used in computing net loss per share attributable to common shareholders - basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Net loss per unit attributable to common unit holders - basic and diluted Net Income Loss Per Outstanding Limited Partnership And General Partnership Unit Basic And Diluted Weighted-average common units used in computing net loss per unit attributable to common unit holders - basic and diluted Weighted Average Number Of Limited Partnership And General Partnership Unit Outstanding Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Net Loss Other comprehensive loss: Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Net unrealized losses on marketable securities Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent Other comprehensive loss Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent Comprehensive loss Comprehensive Income Net Of Tax Temporary equity units issued during period units new issues. Reclassifications of temporary equity, units. Reclassifications of temporary equity. Reclassifications of temporary to permanent equity, shares. Limited liability company LLC preferred units issued during period value new issues. Limited liability company LLC preferred stock issued during period units new issues. Limited liability company LLC preferred units issued during period units new issues. Limited liability company LLC preferred units issued during period new issues shares. Common units issued for license agreement amount. Units repurchased during period units. Units repurchased during period amount. Limited liability company (LLC) exchange of temporary preferred and common units into temporary preferred and common stock, value. Limited liability company LLC exchange of temporary preferred and common units into temporary preferred and common stock, shares. Limited liability company LLC exchange of preferred stock into preferred and common stock value. Limited liability company LLC exchange of preferred stock into preferred and common stock shares. Exchange of common units into preferred and common stock, value. Exchange of common units into preferred and common stock, shares. Limited liability company (L L C) exchange of preferred and common units into preferred and common stock. Limited liability company (LLC) exchange of preferred and common units into preferred and common stock value. Limited liability company LLC exchange of preferred and common units into preferred and common stock, shares. Adjustments to additional paid in capital exchange of preferred and common units into preferred and common stock. Limited liability company LLC temporary convertible preferred stock and contingently redeemable preferred stock exchanged for common stock unit value. Limited liability company LLC temporary convertible preferred stock and contingently redeemable preferred stock exchanged for common stock unit shares. Limited liability company LLC convertible preferred stock and contingently redeemable preferred stock exchanged for common stock unit value. Limited liability company LLC convertible preferred stock and contingently redeemable preferred stock exchanged for common stock unit shares. Stock issued during period value convertible preferred stock and contingently redeemable preferred stock exchange for common stock. Stock issued during period shares convertible preferred stock and contingently redeemable preferred stock exchange for common stock. Stock issued during period value common stock exchanged for common stock. Stock issued during period value in merger. Stock issued during period shares in merger. Stock issued during period shares common stock exchanged for common stock. Statement Of Stockholders Equity [Abstract] Contingently redeemable Class A preferred units Class A preferred units Class B preferred units Class of Stock Statement Class Of Stock [Axis] Class of Stock Class Of Stock [Domain] Contingently redeemable series A preferred stock. Contingently redeemable Series A preferred stock Contingently Redeemable Series A Preferred Stock [Member] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Units [Member] Common units Common Units [Member] Series A convertible preferred stock. Series A Convertible Preferred Stock Series A Convertible Preferred Stock [Member] Series B convertible preferred stock. Series B Convertible Preferred Stock Series B Convertible Preferred Stock [Member] Series C convertible preferred stock. Series C Convertible Preferred Stock Series C Convertible Preferred Stock [Member] Common stock zero point zero zero zero one par. Common Shares $0.0001 Par Common Stock Zero Point Zero Zero Zero One Par [Member] Common stock zero point zero zero one par. Common Shares $0.001 Par Common Stock Zero Point Zero Zero One Par [Member] Additional Paid-in Capital Additional Paid In Capital [Member] Unrealized Gain/(Loss) on Securities Accumulated Net Unrealized Investment Gain Loss [Member] Accumulated Deficit Retained Earnings [Member] Class A three preferred units. Class A-3 Preferred Units Class A Three Preferred Units [Member] Balance Balance (in units) Balance Balance (in units) Balance Balance (in units) Balance Balance (in units) Shares Outstanding Sale of preferred units, net of issuance costs Temporary Equity Stock Issued During Period Value New Issues Sale of preferred units, net of issuance costs (in units) Temporary Equity Units Issued During Period Units New Issues Sale of preferred units, net of issuance costs Limited Liability Company L L C Preferred Units Issued During Period Value New Issues Sale of preferred units, net of issuance costs Limited Liability Company L L C Preferred Stock Issued During Period Units New Issues Sale of preferred units, net of issuance costs (in units) Limited Liability Company L L C Preferred Units Issued During Period Units New Issues Sale of preferred units, net of issuance costs, shares Limited Liability Company L L C Preferred Units Issued During Period New Issues Shares Issuance of common stock for license agreement Common Units Issued For License Agreement Amount Common units issued for license agreement units. Issuance of common stock for license agreement (in units) Common Units Issued For License Agreement Units Repurchase of founders' units Units Repurchased During Period Units Repurchase of founders' units, amount Units Repurchased During Period Amount Exchange of preferred and common units into preferred and common stock Limited Liability Company L L C Exchange Of Temporary Preferred And Common Units Into Temporary Preferred And Common Stock Value Exchange of preferred and common units into preferred and common stock Reclassifications Of Temporary Equity Exchange of preferred and common units into preferred and common stock, Units Reclassifications Of Temporary Equity Units Exchange of preferred and common units into preferred and common stock, (in units) Limited Liability Company L L C Exchange Of Temporary Preferred And Common Units Into Temporary Preferred And Common Stock Shares Exchange of preferred and common units into preferred and common stock Limited Liability Company L L C Exchange Of Preferred Stock Into Preferred And Common Stock Value Exchange of preferred and common units into preferred and common stock, (in units) Limited Liability Company L L C Exchange Of Preferred Stock Into Preferred And Common Stock Shares Exchange of common units into preferred and common stock, value Exchange Of Common Units Into Preferred And Common Stock Value Exchange of common units into preferred and common stock, (in units) Exchange Of Common Units Into Preferred And Common Stock Shares Exchange of preferred and common units into preferred and common stock Limited Liability Company L L C Exchange Of Preferred And Common Units Into Preferred And Common Stock Exchange of preferred and common units into preferred and common stock Limited Liability Company L L C Exchange Of Preferred And Common Units Into Preferred And Common Stock Value Exchange of preferred and common units into preferred and common stock, shares Limited Liability Company L L C Exchange Of Preferred And Common Units Into Preferred And Common Stock Shares Exchange of preferred and common units into preferred and common stock Adjustments To Additional Paid In Capital Exchange Of Preferred And Common Units Into Preferred And Common Stock Sale of preferred stock, net of issuance costs Limited Liability Company L L C Preferred Stock Issued During Period Value New Issues Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock Reclassifications Of Temporary To Permanent Equity Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock, Units Reclassifications Of Temporary To Permanent Equity Shares Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock Limited Liability Company L L C Temporary Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchanged For Common Stock Unit Value Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock, (in units) Limited Liability Company L L C Temporary Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchanged For Common Stock Unit Shares Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock Limited Liability Company L L C Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchanged For Common Stock Unit Value Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock Limited Liability Company L L C Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchanged For Common Stock Unit Shares Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock Stock Issued During Period Value Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchange For Common Stock Convertible preferred stock and contingently redeemable preferred stock exchanged for common stock, shares Stock Issued During Period Shares Convertible Preferred Stock And Contingently Redeemable Preferred Stock Exchange For Common Stock Common stock ($.0001 par) exchanged for common stock ($.001 par) Stock Issued During Period Value Common Stock Exchanged For Common Stock Common stock ($.0001 par) exchanged for common stock ($.001 par), shares Stock Issued During Period Shares Common Stock Exchanged For Common Stock Issuance of common stock in the Merger Stock Issued During Period Value In Merger Issuance of common stock in the Merger, shares Stock Issued During Period Shares In Merger Exercise of stock options Stock Issued During Period Value Stock Options Exercised Exercise of stock options, shares Stock Issued During Period Shares Stock Options Exercised Issuance of restricted stock Stock Issued During Period Value Restricted Stock Award Gross Issuance of restricted stock, shares Stock Issued During Period Shares Restricted Stock Award Gross Cancellation of restricted stock Stock Issued During Period Shares Restricted Stock Award Forfeited Equity-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Effect of adoption of ASU 2016-09 Cumulative Effect On Retained Earnings Net Of Tax1 Unrealized gain/(loss) on securities Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Net Of Tax Balance Balance (in units) Balance Balance (in units) Balance Balance (in units) Balance Balance (in units) Exchanged common stock par or stated value per share. Issuance costs Payments Of Stock Issuance Costs Common shares, par value Exchanged common shares, par value Exchanged Common Stock Par Or Stated Value Per Share Proceeds from stock options exercised and grant of restricted stock. Allowance for tenant improvements. Noncash purchase of property, plant and equipment in accounts payable and accrued liabilities. Assets acquired under capital leases. Prior period adjustment related to adoption of ASU 2016-09. Cash Flow Noncash Investing Disclosure [Abstract] Cash Flow Noncash Financing Activities Disclosure [Abstract] 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] Depreciation Depreciation Loss on disposal of property and equipment Gain Loss On Sale Of Property Plant Equipment Equity-based compensation expense Share Based Compensation Common shares issued for license acquisition Issuance Of Stock And Warrants For Services Or Claims Accretion/amortization of investment securities Accretion Amortization Of Discounts And Premiums Investments 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 and accrued expenses Increase Decrease In Accounts Payable And Accrued Liabilities Deferred revenue Increase Decrease In Deferred Revenue Deferred rent Increase Decrease In Deferred Liabilities Other assets Increase Decrease In Other Operating Assets Net cash, cash equivalents and restricted 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] Net assets acquired in reverse merger, net of transaction costs Payments For Proceeds From Businesses And Interest In Affiliates Purchases of marketable securities Payments To Acquire Available For Sale Securities Proceeds from maturity of marketable securities Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Proceeds from sale of property and equipment Proceeds From Sale Of Property Plant And Equipment Purchases of property and equipment Payments To Acquire Property Plant And Equipment Net cash, cash equivalents and restricted cash provided by (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] Payments on capital lease obligations Repayments Of Long Term Capital Lease Obligations Proceeds from exercise of stock options and grant of restricted stock Proceeds From Stock Options Exercised And Grant Of Restricted Stock Proceeds from sale of convertible preferred stock, net of issuance costs Proceeds From Issuance Of Convertible Preferred Stock Proceeds from sale of preferred units, net of issuance costs Proceeds From Issuance Of Preferred Limited Partners Units Net cash, cash equivalents and restricted cash provided by financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Net increase in cash, cash equivalents and restricted cash Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Excluding Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Cash, cash equivalents and restricted cash at end of period Supplemental disclosure of non-cash investing activities: Cash Flow Noncash Investing Disclosure [Abstract] Landlord funded allowance for tenant improvements Allowance For Tenant Improvements Adjustment for property and equipment purchases included in accounts payable and accrued expenses Noncash Purchase Of Property Plant And Equipment In Accounts Payable And Accrued Liabilities Supplemental disclosure of non-cash financing activities: Cash Flow Noncash Financing Activities Disclosure [Abstract]