Entity Central Index Key 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 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 Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding The amount expected to be received within one year or the normal operating cycle, if longer, as part of a refundable tax incentive program for research and development activities. The amount expected to be received after one year or the normal operating cycle, if longer, as part of a refundable tax incentive program for research and development activities. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets Current [Abstract] Cash and cash equivalents Cash And Cash Equivalents At Carrying Value Marketable securities Available For Sale Securities Debt Securities Current Tax incentive receivable Tax Incentive Receivable 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 Operating lease right-of-use assets Operating Lease Right Of Use Asset Tax incentive receivable, net of current portion Tax Incentive Receivable Noncurrent Restricted cash Restricted Cash 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 and other Accrued Liabilities And Other Liabilities Notes payable, current Notes Payable Current Total current liabilities Liabilities Current Notes payable, long-term Long Term Notes Payable Operating lease liabilities Operating Lease Liability Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 7) Commitments And Contingencies Stockholders' equity: Stockholders Equity [Abstract] Preferred stock; $0.001 par value per share; 5,000,000 shares authorized as of March 31, 2019 and December 31, 2018; no shares issued and outstanding as of March 31, 2019 and December 31, 2018 Preferred Stock Value Common stock, $0.001 par value per share; 115,000,000 shares authorized as of March 31, 2019 and December 31, 2018; 37,323,079 and 37,287,221 shares issued and outstanding as of March 31, 2019 and December 31, 2018, respectively Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Accumulated deficit Retained Earnings Accumulated Deficit Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income Loss Net Of Tax Total stockholders' equity Stockholders Equity Total liabilities and stockholders' equity Liabilities And Stockholders Equity Preferred stock, par value per share 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 per share 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] 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): Other Income And Expenses [Abstract] Interest income Investment Income Net Interest expense Interest Expense Foreign currency transaction gains (losses), net Foreign Currency Transaction Gain Loss Before Tax Total other income (expense), net Nonoperating Income Expense Net loss Net Income Loss Net loss per share, basic and diluted Earnings Per Share Basic And Diluted Weighted average common shares outstanding, basic and diluted Weighted Average Number Of Share Outstanding Basic And Diluted Comprehensive loss: Comprehensive Income Net Of Tax [Abstract] Net loss Other comprehensive income: Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent [Abstract] Unrealized gain on marketable securities Other Comprehensive Income Availableforsale Securities Adjustment Net Of Tax Portion Attributable To Parent Total other comprehensive income Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent Total comprehensive loss Comprehensive Income Net Of Tax The number of shares issued during the period upon exercise of stock options and stock purchase plans. The value of stock issued during the period upon exercise of stock options and stock purchase plans. Statement Of Stockholders Equity [Abstract] Statement [Table] Statement [Table] 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] Accumulated Deficit [Member] Retained Earnings [Member] Accumulated Other Comprehensive Loss [Member] Accumulated Other Comprehensive Income [Member] Statement [Line Items] Statement [Line Items] Beginning balance Beginning balance, shares Shares Outstanding Issuance of common stock upon exercise of stock options and employee stock purchase plan Stock Issued During Period Value Stock Options Exercised And Employee Stock Purchase Plan Issuance of common stock upon exercise of stock options and employee stock purchase plan, shares Stock Issued During Period Shares Stock Options Exercised And Employee Stock Purchase Plans Issuance of restricted stock units Stock Issued During Period Value Restricted Stock Award Net Of Forfeitures Issuance of restricted stock units, shares Stock Issued During Period Shares Restricted Stock Award Net Of Forfeitures Stock-based compensation expense Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Unrealized gain on marketable securities Marketable Securities Unrealized Gain Loss Ending balance Ending balance, shares The cash outflow associated with the premium paid on marketable securities. The increase (decrease) during the reporting period in tax incentive receivable, which represents the amount due from tax authorities. 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] Stock-based compensation expense Share Based Compensation Depreciation expense Depreciation Unrealized foreign currency transaction (gains) losses Foreign Currency Transaction Gain Loss Unrealized Premium on marketable securities, net Premium On Marketable Securities Amortization of discount on marketable securities Investment Income Net Amortization Of Discount And Premium 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 Tax incentive receivable Increase Decrease In Tax Incentives Receivable Accounts payable Increase Decrease In Accounts Payable Accrued expenses and other Increase Decrease In Accrued Liabilities And Other Operating 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] Proceeds from sales and maturities of marketable securities Proceeds From Sale And Maturity Of Available For Sale Securities Purchases of marketable securities Payments To Acquire Available For Sale Securities Debt Purchases of property and equipment Payments To Acquire Property Plant And Equipment Net cash provided by 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 exercise of common stock options and employee stock purchase plan Proceeds From Issuance Of Shares Under Incentive And Share Based Compensation Plans Including Stock Options Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net (decrease) increase in cash, cash equivalents and restricted cash Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash, cash equivalents and restricted cash at beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations Cash, cash equivalents and restricted cash at end of period Supplemental disclosure of non-cash investing and financing activities: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Property and equipment included in accounts payable Capital Expenditures Incurred But Not Yet Paid Supplemental disclosure of cash flow information: Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid Net Accounting Policies [Abstract] Nature of the Business and Basis of Presentation Business Description And Basis Of Presentation [Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements and Marketable Securities Fair Value Disclosures [Text Block] Payables And Accruals [Abstract] Accrued Expenses and Other Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Current [Text Block] Debt Disclosure [Abstract] Notes Payable Debt Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Stock-Based Awards Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Compensation And Retirement Disclosure [Abstract] Retirement Plan Pension And Other Postretirement Benefits Disclosure [Text Block] Research And Development [Abstract] Australia Research and Development Tax Incentive Research Development And Computer Software Disclosure [Text Block] Use of Estimates Use Of Estimates Marketable securities Marketable Securities Policy Net Loss Per Share Earnings Per Share Policy [Text Block] Recently Issued and Adopted Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Summary of Common Stock Equivalents Outstanding Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Text Block] Summary of Cash Equivalents and Marketable Securities Fair Value Assets Measured On Recurring And Nonrecurring Basis Table [Text Block] Summary of Marketable Securities Schedule Of Available For Sale Securities Reconciliation Table [Text Block] Schedule of accrued liabilities and other liabilities. Schedule of Accrued Expenses and Other Schedule Of Accrued Liabilities And Other Liabilities Table [Text Block] Tabular disclosure of notes payable. Includes, but is not limited to, current and long-term portions. Schedule of Notes Payable Schedule Of Notes Payable Table [Text Block] Schedule of Estimated Future Principal Payments Schedule Of Maturities Of Long Term Debt Table [Text Block] Summary of Stock-Based Compensation Expense Related to Stock Options, Restricted Common Stock and ESPP Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Text Block] Schedule of Future Minimum Lease Payments for Operating Leases Lessee Operating Lease Liability Maturity Table [Text Block] Schedule of Components of Leases Expense Lease Cost Table [Text Block] Schedule of supplemental balance sheet information related to leases. Summary of Balance Sheet Information Related to Leases Schedule Of Supplemental Balance Sheet Information Related To Leases Table [Text Block] Schedule of weighted average remaining lease term and weighted average discount rate of operating leases. Schedule of Weighted Average Remaining Lease Term and Weighted Average Discount Rate of Operating Leases Schedule Of Weighted Average Remaining Lease Term And Weighted Average Discount Rate Of Operating Leases Table [Text Block] Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Sale of Stock Subsidiary Sale Of Stock [Axis] Sale of Stock Sale Of Stock Name Of Transaction [Domain] Follow-on offerings. Public Offering [Member] Follow On Offerings [Member] Long-term Debt, Type Longterm Debt Type [Axis] Long-term Debt, Type Longterm Debt Type [Domain] Term Loan [Member] Term Loan [Member] Term Loan [Member] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Entity incorporation date Entity Incorporation Date Of Incorporation Net proceeds from sale of securities. Accumulated deficit Net proceeds from sale of securities Net Proceeds From Sale Of Securities Issuance of common stock Stock Issued During Period Shares New Issues Share price per share Shares Issued Price Per Share Net proceeds from public offering, after underwriting discount, commission and offering expenses Proceeds From Issuance Of Common Stock Aggregate principal balance Debt Instrument Face Amount Loan agreement minimum liquidity required Restricted Cash And Investments Total cash, cash equivalents and marketable securities Cash Cash Equivalents And Short Term Investments Earnings Per Share [Abstract] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table] Antidilutive Securities Antidilutive Securities Excluded From Computation Of Earnings Per Share By Antidilutive Securities [Axis] Antidilutive Securities, Name Antidilutive Securities Name [Domain] Options to Purchase Common Stock [Member] Employee Stock Option [Member] Unvested Restricted Common Stock [Member] Restricted Stock [Member] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items] Total potentially dilutive shares Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount New Accounting Pronouncements Or Change In Accounting Principle [Table] New Accounting Pronouncements Or Change In Accounting Principle [Table] Adjustments for New Accounting Pronouncements Adjustments For New Accounting Pronouncements [Axis] Type of Adoption Type Of Adoption [Member] ASU 2016-02 [Member] Accounting Standards Update201602 [Member] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] New Accounting Pronouncements Or Change In Accounting Principle [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Quoted Prices in Active Markets, (Level 1) [Member] Fair Value Inputs Level1 [Member] Significant Other Observable Inputs (Level 2) [Member] Fair Value Inputs Level2 [Member] Significant Unobservable Inputs (Level 3) [Member] Fair Value Inputs Level3 [Member] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] Money Market Funds [Member] Money Market Funds [Member] Commercial Paper [Member] Commercial Paper [Member] U.S. Government Securities [Member] U S Government Corporations And Agencies Securities [Member] Corporate Bonds [Member] Corporate Bond Securities [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] Cash equivalents Cash And Cash Equivalents Fair Value Disclosure Total cash equivalents and marketable securities Assets Fair Value Disclosure Debt Securities Available For Sale [Table] Debt Securities Available For Sale [Table] Corporate Bonds (Due within 1 Year) [Member] Commercial Paper (Due within 1 Year) [Member] U.S. Government Securities (Due within 1 Year) [Member] Schedule of Available-for-sale Securities [Line Items] Schedule Of Available For Sale Securities [Line Items] Amortized Cost Available For Sale Debt Securities Amortized Cost Basis Gross Unrealized Gains Available For Sale Debt Securities Accumulated Gross Unrealized Gain Before Tax Gross Unrealized Losses Available For Sale Debt Securities Accumulated Gross Unrealized Loss Before Tax Fair Value Carrying value as of the balance sheet date of obligations incurred through that date and payable for expenses related to research and development. 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 expenses Accrued Research And Development Expense Current Accrued payroll and related expenses Employee Related Liabilities Current Accrued professional fees Accrued Professional Fees Current Operating lease liabilities Operating Lease Liability Current Accrued other Other Accrued Liabilities Current Total accrued expenses and other Debt Instrument [Table] Debt Instrument [Table] Range Range [Axis] Range Range [Member] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Debt Instrument [Line Items] Debt Instrument [Line Items] Maximum borrowings under term loan Proceeds from issuance of notes payable Proceeds From Notes Payable The fee, as a percentage of the term loan, due as a final payment. Debt facility description Debt Instrument Description Debt maturity date Debt Instrument Maturity Date Debt facility interest rate description Debt Instrument Description Of Variable Rate Basis Debt facility variable interest at annual rate Debt Instrument Basis Spread On Variable Rate1 Debt facility effective interest rate Debt Instrument Interest Rate Effective Percentage Debt facility fee percentage Debt Instrument Fee Percentage Charges to interest expense of debt outstanding Debt Instrument Increase Accrued Interest Restricted cash and investments as percentage of outstanding principal amount. Percentage equivalent of cash, cash equivalents and marketable securities balance Restricted Cash And Investments As Percentage Of Outstanding Principal Amount The percentage of its cash, cash equivalents, and marketable securities that the Company is obligated to maintain a balance of. The percentage of the principal balance that the Company must immediately secure if it does not meet its balance obligations of cash, cash equivalents and marketable securities. Debt facility covenant description Debt Instrument Covenant Description Unrestricted cash, cash equivalents and marketable securties Percentage of cash, cash equivalents and marketable securities Cash Cash Equivalents And Short Term Investments Percentage Percentage of principal balance to be secured in restricted cash account for not to be considered an event of default Percentage Of Principal Balance To Be Secured In Restricted Cash Account The aggregate amount of cash permitted to be maintained by the Australian subsidiary. Aggregate value of cash maintained by Australian subsidiary, limit Debt Instrument Restrictive Covenants Investment In Subsidiaries The minimum default amount over which the lender may exercise remedies against the Company. Credit facility default amount Line Of Credit Facility Debt Default Minimum Amount Carrying value as of the balance sheet date of notes payable before accretion (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Debt Instruments [Abstract] Notes payable Notes Payable Less: current portion Notes payable, net of current portion Long Term Notes Payable Before Accretion Accretion related to final payment Debt Instrument Periodic Payment Terms Balloon Payment To Be Paid Notes payable, long term 2019 (April - December) Long Term Debt Maturities Repayments Of Principal Remainder Of Fiscal Year 2020 Long Term Debt Maturities Repayments Of Principal In Year Two 2021 Long Term Debt Maturities Repayments Of Principal In Year Three Total Long Term Debt Interest expense on term loan Debt Instrument Periodic Payment Interest Debt facility effective interest rate Debt Instrument Interest Rate During Period Compensation Related Costs [Abstract] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Two Thousand Fourteen Stock Option [Member] 2014 Stock Option and Incentive Plan [Member] Two Thousand Fourteen Stock Option [Member] Two thousand and fourteen employee stock purchase plan. 2014 Employee Stock Purchase Plan [Member] Two Thousand And Fourteen Employee Stock Purchase Plan [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share Based Compensation Arrangement By Share Based Payment Award [Line Items] Common stock available for issuance Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant Shares added to plan Share Based Compensation Arrangement By Share Based Payment Award Options Other Increases Decreases In Period Income Statement Location Income Statement Location [Axis] Income Statement Location Income Statement Location [Domain] Research and Development [Member] Research And Development Expense [Member] General and Administrative [Member] General And Administrative Expense [Member] Total stock-based compensation expense Allocated Share Based Compensation Expense Area of office space. Other Commitments [Table] Other Commitments [Table] Entity by Location Entity By Location [Axis] Location Location [Domain] Boston Center Plaza, Boston [Member] Boston [Member] Geographical Statement Geographical [Axis] Geographical Segment Geographical [Domain] Massachusetts [Member] MASSACHUSETTS Lease Arrangement, Type Lease Arrangement Type [Axis] Lease Arrangement, Type Lease Arrangement Type [Domain] Shigo Center Plaza Owners LLC. Shigo Center Plaza Owners LLC [Member] Shigo Center Plaza Owners L L C [Member] Office Space Lease [Member] Boston Office Space [Member] Office Space Lease [Member] Additional Office Space [Member] Additional Boston Office Space [Member] Additional Office Space [Member] Additional Office Space two [Member] San Diego Office Space [Member] Additional Office Space Two [Member] Counterparty Name Counterparty Name [Axis] Counterparty Name Repurchase Agreement Counterparty Name [Domain] Unrelated Third Party Member Unrelated Third Party [Member] Unrelated Third Party [Member] Scenario Statement Scenario [Axis] Scenario, Unspecified Scenario Unspecified [Domain] Scenario Forecast [Member] Scenario Forecast [Member] Category of Item Purchased Long Term Purchase Commitment By Category Of Item Purchased [Axis] Long-term Purchase Commitment, Category of Item Purchased Long Term Purchase Commitment Category Of Item Purchased [Domain] Pre Commercialization Milestones [Member] Pre Commercialization Milestones [Member] Pre Commercialization Milestones [Member] Product Commercialization Milestones [Member] Product Commercialization Milestones [Member] Product Commercialization Milestones [Member] Subsequent Licensed Product [Member] Subsequent Licensed Product [Member] Subsequent Licensed Product [Member] Development Based Milestones [Member] Development Based Milestones [Member] Development Based Milestones [Member] Other Commitments [Line Items] Other Commitments [Line Items] Area of office space Area Of Office Space Operating lease term Lessee Operating Lease Term Of Contract Lease extension period Lessee Operating Lease Renewal Term Letter of credit Line Of Credit Operating lease, existence of option to extend Lessee Operating Lease Existence Of Option To Extend Total lease payments over the initial term Lessee Operating Lease Liability Payments Due The number of options available to extend an operating lease. Sublease area of real estate property. Sublease Expiration Date Lease expiration date Lease Expiration Date1 Number of options to extend lease Operating Leases Number Of Options To Extend Lease Subleased area Sublease Area Of Real Estate Property Sublease expiration date Sublease Expiration Date Sublease rental income Sublease Income Leases [Abstract] 2019 (April - December) Lessee Operating Lease Liability Payments Remainder Of Fiscal Year 2020 Lessee Operating Lease Liability Payments Due Year Two 2021 Lessee Operating Lease Liability Payments Due Year Three 2022 Lessee Operating Lease Liability Payments Due Year Four 2023 Lessee Operating Lease Liability Payments Due Year Five Thereafter Lessee Operating Lease Liability Payments Due After Year Five Total lease payments Less: imputed interest Lessee Operating Lease Liability Undiscounted Excess Amount Total Operating Lease Liability 2019 Operating Leases Future Minimum Payments Remainder Of Fiscal Year 2020 Operating Leases Future Minimum Payments Due In Two Years 2021 Operating Leases Future Minimum Payments Due In Three Years 2022 Operating Leases Future Minimum Payments Due In Four Years 2023 Operating Leases Future Minimum Payments Due In Five Years Thereafter Operating Leases Future Minimum Payments Due Thereafter Total lease payments Operating Leases Future Minimum Payments Due Lease expense Lease Cost Operating lease cost Operating Lease Cost Short-term lease cost Short Term Lease Cost Sublease income Total lease cost Operating lease, rental expense Operating Lease Expense Liabilities Liabilities [Abstract] Accrued expenses - current operating lease liabilities Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] Operating Lease Liability Current Statement Of Financial Position Extensible List Total operating lease liabilities Weighted average remaining lease term in years Operating Lease Weighted Average Remaining Lease Term1 Weighted average discount rate Operating Lease Weighted Average Discount Rate Percent Operating cash flows from operating leases Operating Lease Payments Amount of payment due upon reaching milestone. Maximum fee the Company is obligated to pay per licensed product. Milestone payments Milestone Payment Amount Licensing fees per product maximum Licensing Fees Per Product Maximum Amount of payment due for milestones that have been achieved Milestone payments due Milestone Liability Defined Contribution Plan [Table] Defined Contribution Plan [Table] Retirement Plan Type Retirement Plan Type [Axis] Retirement Plan Type Retirement Plan Type [Domain] Retirement 401K plan. Retirement 401K Plan [Member] Retirement401 K Plan [Member] Defined Contribution Plan Disclosure [Line Items] Defined Contribution Plan Disclosure [Line Items] Percentage of employer's contribution on employee's base salary Defined Contribution Plan Employer Matching Contribution Percent Contribution expense Defined Contribution Plan Cost Recognized The percentage to be refunded pertaining to the tax incentive for qualified research and development activities. The amount of reduction to research and development expense recorded in the income statement. The percentage of research and development costs to be reduced. Tax incentive receivable. Research and Development Tax Incentive [Line Items] Research and Development Expenses [Table] Research And Development Expenses [Table] Research And Development Expenses [Table] Consolidated Entities Consolidated Entities [Axis] Consolidated Entities Consolidated Entities [Domain] Zafgen Australia Pty Limited [Member] Subsidiaries [Member] Australia [Member] AUSTRALIA Research and Development Tax Incentive [Line Items] Research And Development Tax Incentive [Line Items] Percentage of refundable tax incentive Effective Tax Incentive Rate Related To Research And Development Reduction to research and development expenses Tax Incentive Research And Development Activities Percentage of reduction in research and development costs Percentage Reduction Research And Development Costs Unrealized foreign currency exchange gains (losses) Tax incentive receivable Tax Incentive Receivable