Accounting Policies [Abstract] Schedule of Cash and Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of Restricted Cash and Cash Equivalents Restrictions on Cash and Cash Equivalents [Table Text Block] Components of Accumulated Other Comprehensive Income (Loss), Net of Tax Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Revenue from Contract with Customer [Abstract] Revenue Arrangements Revenue from Contract with Customer [Text Block] Statement of Financial Position [Abstract] Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Restricted cash Restricted Cash, Current Accounts receivable Accounts Receivable, after Allowance for Credit Loss, 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 Right-of-use asset, net Operating Lease, Right-of-Use Asset Long-term restricted cash Restricted Cash and Investments, Noncurrent Total assets Assets Liabilities and stockholders’ equity (deficit) Liabilities and Equity [Abstract] Current liabilities: Liabilities, Current [Abstract] Accounts payable Accounts Payable, Current Accrued expenses Accrued Liabilities, Current Loan payable Loans Payable, Current Lease liability Operating Lease, Liability, Current Deferred revenue Contract with Customer, Liability, Current Total current liabilities Liabilities, Current Non‑current liabilities: Other Liabilities, Noncurrent [Abstract] Deferred revenue Contract with Customer, Liability, Noncurrent Warrant liabilities Warrants and Rights Outstanding Other long‑term liabilities Other Liabilities, Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 17) Commitments and Contingencies Stockholders’ equity (deficit): Stockholders' Equity Attributable to Parent [Abstract] Preferred stock, $0.0001 par value; 10,000,000 shares authorized; no shares issued and outstanding at December 31, 2019 and December 31, 2018, respectively Preferred Stock, Value, Issued Common stock, $0.0001 par value; 200,000,000 shares authorized; 86,325,547 and 22,471,776 shares issued and outstanding as of December 31, 2019 and December 31, 2018, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated deficit Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity (deficit) Stockholders' Equity Attributable to Parent Total liabilities and stockholders’ equity (deficit) Liabilities and Equity Related Party Transactions [Abstract] Related-Party Transactions Related Party Transactions Disclosure [Text Block] Leases [Abstract] 2019 Operating Leases, Future Minimum Payments, Remainder of Fiscal Year 2020 Operating Leases, Future Minimum Payments, Due in Two Years Total minimum lease payments Operating Leases, Future Minimum Payments Due Debt Disclosure [Abstract] Schedule of Future Minimum Payments on the Term Loans Schedule of Maturities of Long-term Debt [Table Text Block] Investments, Debt and Equity Securities [Abstract] Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Liability Class [Axis] Liability Class [Axis] Fair Value by Liability Class [Domain] Fair Value by Liability Class [Domain] Warrant Warrant [Member] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Axis] Other Comprehensive Income Location [Domain] Other Comprehensive Income Location [Domain] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Fair value as of December 31, 2018 Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability Value Warrants issued in connection with December 2019 private placement Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Issuances Change in fair value Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Earnings Fair value as of December 31, 2019 Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Table] Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Axis] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] Research and Development Arrangement, Contract to Perform for Others, Type [Domain] Spark License Agreement License Agreement Terms [Member] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] License and Supply Obligation License And Supply Obligation [Member] License And Supply Obligation [Member] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items] Remaining performance obligation, period Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Non-employee stock options Non Employee Stock Option [Member] An arrangement whereby a non-employee is entitled to receive in the future, subject to vesting and other restrictions, a number of shares in the entity at a specified price, as defined in the agreement. Title of Individual [Axis] Title of Individual [Axis] Title of Individual [Domain] Title of Individual [Domain] Director Director [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Founders Founder [Member] Represents information pertaining to founder member. Related Party Transaction [Axis] Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Quarterly payment Quarterly Payment [Member] Quarterly Payment [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Related party transaction, amounts of transaction Related Party Transaction, Amounts of Transaction Options granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Consulting services expenses Related Party Transaction, Expenses from Transactions with Related Party Share-based Payment Arrangement [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] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Schedule of Weighted Average Assumptions Used Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Summary of Activity Under the 2008 Plan and the 2016 Plan Share-based Payment Arrangement, Option, Activity [Table Text Block] Disclosure of Share-based Compensation Arrangements by Share-based Payment Award Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] Schedule of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock Share-based Payment Arrangement, Cost by Plan [Table Text Block] Operating lease, weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Operating lease, weighted average discount rate, percent Operating Lease, Weighted Average Discount Rate, Percent Unvested restricted stock units Restricted Stock Units (RSUs) [Member] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Shares outstanding at December 31, 2018 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Grants in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Shares outstanding at March 31, 2019 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Shares outstanding at December 31, 2018 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Grants in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Vested in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited in period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Shares outstanding at March 31, 2019 (in dollars per share) Stock‑based compensation expense Share-based Payment Arrangement, Expense Weighted average period for recognition Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Schedule of Changes in Contract Liabilities Contract with Customer, Asset and Liability [Table Text Block] Cover page. Document Type Document Type Document Annual Report Document Annual Report Document Period End Date Document Period End Date Document Transition Report Document Transition Report Entity File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name 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 Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Smaller Reporting Company Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Extended Transition Period Entity Ex Transition Period Entity Shell Company Entity Shell Company Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Documents Incorporated by Reference Documents Incorporated by Reference [Text Block] Amendment Flag Amendment Flag Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] December 2019 Financing December Two Thousand Nineteen Financing [Member] December Two Thousand Nineteen Financing [Member] Private Placement Private Placement [Member] Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] 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] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Aggregate shares of common stock at a purchase price (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Purchased for Award Statement of Comprehensive Income [Abstract] Grant and collaboration revenue Revenue from Contract with Customer, Excluding Assessed Tax Operating expenses: Cost of Revenue [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) Investment income Investment Income, Net Loss on extinguishment of debt Gain (Loss) on Extinguishment of Debt Foreign currency transaction (loss), net Foreign Currency Transaction Gain (Loss), before Tax Interest expense Interest Expense Change in fair value of warrant liabilities Fair Value Adjustment of Warrants Other (expense), net Other Nonoperating Income (Expense) Net loss Net Income (Loss) Attributable to Parent Other comprehensive loss: Other Comprehensive Income (Loss), Tax [Abstract] Foreign currency translation adjustment Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax Unrealized gain on securities Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax Total comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Net loss per share: Earnings Per Share, Basic and Diluted [Abstract] Net loss per share attributable to common stockholders—basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic and diluted (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Summary of Assets Measured at Fair Value on a Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of Fair Value Measurement Inputs and Valuation Techniques Fair Value Measurement Inputs and Valuation Techniques [Table Text Block] Schedule Of Changes In The Warrant Liabilities Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] The 2008 Plan and the 2016 Plan The 2008 Plan And The 2016 Plan [Member] The 2008 Plan And The 2016 Plan [Member] 2008 Plan Stock Incentive Plan2008 [Member] Represents the information pertaining to the 2008 stock incentive plan, which provides for the granting of stock based awards to employees, directors, and consultants under terms and provisions established by the board of directors. 2016 Plan Stock Incentive Plan2016 [Member] Represents the information pertaining to the 2016 stock incentive plan, which provides for the granting of stock based awards to employees, directors, and consultants under terms and provisions established by the board of directors. Employment Inducement Incentive Award Plan Employment Inducement Incentive Award Plan [Member] Employment Inducement Incentive Award Plan [Member] ESPP Employee Stock Purchase Plan2016 [Member] Represent information pertaining to the 2016 Employee Stock Purchase Plan. Employee stock option grants Share-based Payment Arrangement [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Tranche One Share-based Payment Arrangement, Tranche One [Member] Tranche Two Share-based Payment Arrangement, Tranche Two [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Number of shares authorized for grants (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Automatic increase in the number of shares that may be issued (as a percent) Employee Stock Purchase Plan Maximum Percentage Of Shares Reserved Based On Shares Outstanding The maximum percentage increase in the shares reserved for future issuance each year based on the number of common stock outstanding at the last day of the year. Number of shares authorized, increase (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Shares Available For Grant, Increase (Decrease) Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Shares Available For Grant, Increase (Decrease) Common stock authorized and reserved for future issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Exercise price of incentive stock options (not less than) Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Combined voting power of participants (as a percent) Share-based Compensation Arrangement By Share-based Payment Award, Voting Rights of Common Stock, Holding Percentage Represents the percentage of voting rights of all classes of stock held by the employees. Award vesting term Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Award expiration term Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Reserved for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease) Estimated forfeitures rate Share-based Compensation Arrangement By Share-based Payment Award Forfeitures Rate Represents the percentage of forfeitures rate of the stock options based on the historical trends. Weighted average grant date fair value of stock options (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Issuance of common stock upon exercise of options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Aggregate intrinsic value of stock options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Unrecognized compensation expense related to unvested employee stock options Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Vested and expected to vest (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Vested and expected to vest, exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number share-based payment, plan modification incremental cost Share-based Payment Arrangement, Plan Modification, Incremental Cost Unrecognized compensation expense related to unvested non-employee stock options Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options Unrecognized compensation expense related to unvested non-employee stock options, period Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options, Period Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options, Period Shares issued, value Stock Issued During Period, Value, New Issues Unrecognized compensation expense Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Organization, Consolidation and Presentation of Financial Statements [Abstract] Nature of the Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Letter of credit Letter of Credit [Member] Lease Arrangement [Axis] Lease Arrangement [Axis] Lease Arrangement [Axis] Lease Arrangement [Domain] Lease Arrangement [Domain] [Domain] for Lease Arrangement [Axis] Laboratory and office space Laboratory And Office Space [Member] Represents information pertaining to laboratory and office space member. 75 North Beacon, Watertown, MA 75 North Beacon, Watertown, MA [Member] 75 North Beacon, Watertown, MA [Member] 65 Grove Street, Watertown,MA 65 Grove Street, Watertown,MA [Member] 65 Grove Street, Watertown,MA [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Right of use asset, net Lease liabilities Operating Lease, Liability Deferred rent and incentives Deferred Rent Credit Operating lease, remaining lease term Operating Lease, Remaining Lease Term Operating Lease, Remaining Lease Term Discount rate Lessee, Operating Lease, Discount Rate Term of contract Lessee, Operating Lease, Term of Contract Renewal term Lessee, Operating Lease, Renewal Term Leasehold improvements gross Leasehold Improvements, Gross Restricted cash Restricted Cash Area of additional office space leased Area of Real Estate Property Lessee-paid construction costs Lease, Cost Operating lease, expense Operating Lease, Expense operating lease payments due Lessee, Operating Lease, Liability, Payments, Due Accumulated deficit Schedule of Cash and Cash Equivalents [Table] Schedule of Cash and Cash Equivalents [Table] Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] Russian subsidiary RUSSIAN FEDERATION Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Unrestricted cash Unrestricted Cash [Member] Unrestricted Cash [Member] Cash and Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Restricted cash and cash equivalents Restricted Cash and Cash Equivalents Lessee, Lease, Description [Table] Lessee, Lease, Description [Table] Lessee, Lease, Description [Line Items] Lessee, Lease, Description [Line Items] 2020 Other Commitment, Due In Next Rolling Twelve Months Other Commitment, Due In Next Rolling Twelve Months 2021 Other Commitment, Due In Rolling Year Two Other Commitment, Due In Rolling Year Two 2022 Other Commitment, Due In Rolling Year Three Other Commitment, Due In Rolling Year Three 2023 Other Commitment, Due In Rolling Year Four Other Commitment, Due In Rolling Year Four 2024 Other Commitment, Due In Rolling Year Five Other Commitment, Due In Rolling Year Five Thereafter Other Commitment, Due After Rolling Year Five Other Commitment, Due After Rolling Year Five Total New Headquarters Lease commitment Other Commitment Equity [Abstract] Equity Stockholders' Equity Note Disclosure [Text Block] Concentration Risk [Table] Concentration Risk [Table] Russian subsidiary Concentration Risk [Line Items] Concentration Risk [Line Items] Cash maintained in Russian bank accounts Cash Retirement Benefits [Abstract] Defined Contribution Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Quarterly Financial Information Disclosure [Abstract] Selected Quarterly Financial Data Quarterly Financial Information [Text Block] Schedule of Future Minimum Lease Payments Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Minimum Rental Commitments Other Commitments [Table Text Block] Schedule of Lease, Cost Lease, Cost [Table Text Block] Schedule of Lessee, Operating Lease, Liability, Maturity Lessee, Operating Lease, Liability, Maturity [Table Text Block] Line of Credit Facility [Table] Line of Credit Facility [Table] 2017 Term Loans 2017 Term Loans [Member] 2017 Term Loans [Member] Term Loans Term Loan [Member] Represents information pertaining to term loan member. Debt Covenant Period [Axis] Debt Covenant Period [Axis] Debt Covenant Period [Axis] Debt Covenant Period [Domain] Debt Covenant Period [Domain] [Domain] for Debt Covenant Period [Axis] Prepaid after second anniversary Term Loan Prepaid After Second Anniversary [Member] Represents information pertaining to prepayment of term loan after second anniversary. Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] Base Rate Base Rate [Member] Outstanding Balances Outstanding Balances [Member] Outstanding Balances [Member] Line of Credit Facility [Line Items] Line of Credit Facility [Line Items] Term loan facility Long-term Line of Credit Repayments of debt Repayments of Lines of Credit Loss on extinguishment of debt Debt issuance costs, line of credit arrangements (less than) Debt Issuance Costs, Line of Credit Arrangements, Net Prepayment fee (as a percent) Early Extinguishment Of Debt, Prepayment Fee Percentage Percentage of fee payable on early extinguishment of debt. Interest rate per annum Line of Credit Facility, Interest Rate During Period Minimum assets trigger Debt Instrument, Event Of Default, Minimum Assets Trigger Debt Instrument, Event Of Default, Minimum Assets Trigger Minimum amount in excess of indebtedness trigger Debt Instrument, Event Of Default, Minimum Amount In Excess Of Indebtedness Trigger Debt Instrument, Event Of Default, Minimum Amount In Excess Of Indebtedness Trigger Final payment fee (as a percent) Final Payment Fee Percentage Percentage of final fee payment payable on aggregate principal amounts borrowed. Final payment fee Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid Debt instrument, basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Interest expense related to the Term Loan Operating lease expense Operating Lease, Cost Variable lease expense Variable Lease, Cost Short-term lease expense Short-term Lease, Cost Total lease expense Contract liabilities: Change In Contract With Customer, Liability [Roll Forward] Change In Contract With Customer, Liability [Roll Forward] Deferred revenue, beginning of period Contract with Customer, Liability, Deferred Revenue Contract with Customer, Liability, Deferred Revenue Other liabilities, beginning of period Contract with Customer, Liability, Other Contract with Customer, Liability, Other Contract liabilities, beginning of period Contract with Customer, Liability Deferred revenue, additions Contract with Customer, Liability, Deferred Revenue, Increase From Cash Receipts Contract with Customer, Liability, Deferred Revenue, Increase From Cash Receipts Other liabilities, additions Contract with Customer, Liability, Other, Increase From Cash Receipts Contract with Customer, Liability, Other, Increase From Cash Receipts Contract liabilities, additions Contract with Customer, Liability, Increase From Cash Receipts Contract with Customer, Liability, Increase From Cash Receipts Deferred revenue, deductions Contract with Customer, Liability, Deferred Revenue, Revenue Recognized Contract with Customer, Liability, Deferred Revenue, Revenue Recognized Other liabilities, deductions Contract with Customer, Liability, Other, Revenue Recognized Contract with Customer, Liability, Other, Revenue Recognized Contract liabilities, deductions Contract with Customer, Liability, Revenue Recognized Deferred revenue, end of period Other liabilities, end of period Contract liabilities, end of period Vesting period Defined Contribution Plan Employers Matching Contribution Vesting Period Period which an employee's right to exercise a plan is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Employer contribution made Defined Contribution Plan, Cost Property, Plant and Equipment [Abstract] Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Adjustments due to ASU 2014-09 Difference between Revenue Guidance in Effect before and after Topic 606 [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Grant Revenue Grant [Member] Accumulated deficit Retained Earnings [Member] ASU 2014-09 Accounting Standards Update 2014-09 [Member] License Agreement For Pompe Disease [Member] License Agreement For Pompe Disease [Member] License Agreement For Pompe Disease [Member] First Acquisition Right First Acquisition Right [Member] First Acquisition Right [Member] Skolkovo Russia Vased Development Fund Of New Technologies Development And Commercialization Center Grant Agreement [Member] Represents information pertaining to russi vased development fund of new technologies development and commercialization center grant agreement. Second Acquisition Right Second Acquisition Right [Member] Second Acquisition Right [Member] Spark Letter Agreement Spark Letter Agreement [Member] Spark Letter Agreement [Member] MIT Exclusive Patent License Agreement With Massachusetts Institute Of Technology [Member] Represents information pertaining to Exclusive patent license agreement with Massachusetts Institute of Technology. " Consideration for Promises Consideration For Promises [Member] Consideration For Promises [Member] Development Milestones Development Milestones [Member] Development Milestones [Member] Regulatory Milestones Regulatory Milestones [Member] Regulatory Milestones [Member] Commercial Milestones Commercial Milestones [Member] Commercial Milestones [Member] Discount on Option Obligation Discount On Option Obligation [Member] Discount On Option Obligation [Member] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Long-term contract liability Upfront cash payment License And Option Agreement, Upfront Cash Payment License And Option Agreement, Upfront Cash Payment Initial Up-front cash payment License And Option Agreement, Initial Up-Front Cash Payment License And Option Agreement, Initial Up-Front Cash Payment Initial Upfront execution fee payment License And Option Agreement, Execution Fee Payment License And Option Agreement, Execution Fee Payment Short-term contract liability Aggregate additional payments due within twelve months License And Option Agreement, Aggregate Additional Payments Due Within Twelve Months Of Contract Date License And Option Agreement, Aggregate Additional Payments Due Within Twelve Months Of Contract Date Term loan number of payments Term Loan Number of Payments Term Loan Number of Payments Two payments due within 12 months of contract date License And Option Agreement, Two Payments Due Within Twelve Months Of Contract Date License And Option Agreement, Two Payments Due Within Twelve Months Of Contract Date Number of additional targets License And Option Agreement, Number Of Additional Targets For Which Other Party May Exercise Options For Additional Licenses License And Option Agreement, Number Of Additional Targets For Which Other Party May Exercise Options For Additional Licenses Variable fee the Company is eligible to receive for each additional target option elected License And Option Agreement, Variable Fee To Be Received For Each Additional Target Option Elected License And Option Agreement, Variable Fee To Be Received For Each Additional Target Option Elected Election period to exercise additional targets License And Option Agreement, Period For Other Party To Exercise Options For Additional Licenses License And Option Agreement, Period For Other Party To Exercise Options For Additional Licenses Additional development and regulatory milestone payments License And Option Agreement, Additional Development And Regulatory Milestone Payments That May Be Received License And Option Agreement, Additional Development And Regulatory Milestone Payments That May Be Received Commercialization milestone payments License And Option Agreement, Commercialization Milestone Payments That May Be Received License And Option Agreement, Commercialization Milestone Payments That May Be Received Sales milestone payments License And Option Agreement, Sales Milestone Payments That May Be Received License And Option Agreement, Sales Milestone Payments That May Be Received Number of obligations Revenue, Number Of Performance Obligations Revenue, Number Of Performance Obligations Period after first commercial sale when the Company is eligible to receive royalties Eligible Period To Receive Royalties Eligible Period To Receive Royalties Period for prior written notice to terminate license Period For Prior Written Notice To Terminate License Represents information pertaining to period for prior written notice to terminate license. Sale of stock, number of shares issued in transaction (in shares) Sale of Stock, Number of Shares Issued in Transaction Sale common stock Sale of Stock, Consideration Received on Transaction Share price (in dollars per share) Sale of Stock, Price Per Share Premium of average daily VWAP (as a percent) Premium Of Average Daily Volume Weighted Average Price Of Common Stock, Percent Premium Of Average Daily Volume Weighted Average Price Of Common Stock, Percent Deferred revenue related to agreement Aggregate purchase price Aggregate Purchase Price Aggregate Purchase Price Aggregate price of shares Spark will have the right to purchase Stock Purchase Agreement, Authorized Amount Of Stock To Sell Stock Purchase Agreement, Authorized Amount Of Stock To Sell Number of shares authorized to be issued pursuant to the Stock Purchase Agreement (in shares) Stock Purchase Program, Number Of Shares Authorized To Be Sold Stock Purchase Program, Number Of Shares Authorized To Be Sold License and option agreement, additional sub-license payment received liability License And Option Agreement, Additional Sub-License Payment Received Liability License And Option Agreement, Additional Sub-License Payment Received Liability License and option agreement, payments made relative to calculated premium paid for initial equity investment made under the purchase agreement License And Option Agreement, Calculated Premium Paid For Equity Investment Under Purchase Agreement License And Option Agreement, Calculated Premium Paid For Equity Investment Under Purchase Agreement Number of agreements combined and evaluated into a single agreement Number Of Agreements Combined Into Single Agreement For Evaluation Number Of Agreements Combined Into Single Agreement For Evaluation Fair value of initial purchase of common stock combined with the embedded future stock Acquisition Rights Stock Issued During Period, Value, Purchase of Assets Performance obligation per each option Revenue, Remaining Performance Obligation, Each Option Revenue, Remaining Performance Obligation, Each Option Revenue recognized Aggregate purchase price per share (in dollar per share) Stock Purchase Program, Aggregate Purchase Price Per Share Stock Purchase Program, Aggregate Purchase Price Per Share Payments received Increase Decrease In Contingently Repayable Grant Funding The increase (decrease) during the reporting period in contingently repayable grant funding that are used in an entity's business. Adoption of new accounting principle Cumulative Effect of New Accounting Principle in Period of Adoption Grants from entities, unused grant funds Grants From Entities Unused Grant Funds Grants From Entities Unused Grant Funds Overspent costs Overspent Costs Overspent Costs Reimbursement invoices Reimbursement Invoice Reimbursement Invoice Number of offering periods under the ESPP Number Of Offering Periods Number Of Offering Periods Term of each offering period Offering Period Offering Period Eligible compensation withheld for use (up to) (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate Purchase price of shares (not less than) (as a percent) Number of shares of common stock outstanding (as a percent) Shares of common stock issued to employees under the ESPP (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Stock-based compensation expense Depreciation expense Depreciation Accelerated depreciation expense Plant Property And Equipment, Accelerated Depreciation Plant Property And Equipment, Accelerated Depreciation Income Tax Disclosure [Abstract] Statutory U.S. federal rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent State income taxes - net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Permanent items Effective Income Tax Rate Reconciliation, Nondeductible Expense, Percent Research tax credits/other Effective Income Tax Rate Reconciliation, Tax Credit, Percent Change in enacted rates Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Valuation allowance, net Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Other Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Stock Incentive Plans Share-based Payment Arrangement [Text Block] Statement of Cash Flows [Abstract] Statement [Table] Statement [Table] At-The-Market Offering At-The-Market Offering [Member] At-The-Market Offering [Member] Note Warrant Note Warrant [Member] Statement [Line Items] Statement [Line Items] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net 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 Amortization of premiums (accretion of discounts) on investments Accretion (Amortization) of Discounts and Premiums, Investments Amortization of right-of-use assets Finance Lease, Right-of-Use Asset, Amortization Loss (gain) on disposal of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Stock‑based compensation expense Share-based Payment Arrangement, Noncash Expense Non‑cash interest expense Paid-in-Kind Interest Warrant liabilities revaluation Net realized losses on investments Realized Investment Gains (Losses) Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Accounts receivable Increase (Decrease) in Accounts Receivable Prepaid expenses, deposits and other assets Increase (Decrease) in Prepaid Expense and Other Assets Accounts payable Increase (Decrease) in Accounts Payable Deferred revenue Increase (Decrease) in Contract with Customer, Liability Accrued expenses and other liabilities 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, Continuing Operations [Abstract] Receipts from the maturity of short-term investments Proceeds from Maturities, Prepayments and Calls of Short-term Investments Purchases of short-term investments Payments to Acquire Short-term Investments Sale of short term investments Proceeds from Sale of Short-term Investments Purchases of property and equipment Payments to Acquire Property, Plant, and Equipment Proceeds from the sale of property and equipment Proceeds from Sale of Property, Plant, and Equipment 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, Continuing Operations [Abstract] Proceeds from issuance of long-term debt, net of expenses Proceeds from Lines of Credit Repayments of principal on outstanding debt Repayments of Long-term Debt Net proceeds from issuance of common stock Proceeds from Issuance of Common Stock Proceeds from exercise of stock options Proceeds from Stock Options Exercised Proceeds from issuance of common stock under Employee Stock Purchase Plan Proceeds from Stock Plans Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Effect of exchange rate changes on cash Effect of Exchange Rate on Cash and Cash Equivalents Net change 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, and restricted cash at end of period Supplement cash flow information Supplemental Cash Flow Information [Abstract] Cash paid for interest Interest Paid, Excluding Capitalized Interest, Operating Activities Noncash investing and financing activities Noncash Investing and Financing Items [Abstract] Purchase of property and equipment not yet paid Capital Expenditures Incurred but Not yet Paid Issuance costs in connection with common stock, common warrants, and pre-funded warrants in accrued liabilities Equity Offering Costs In Accrued Liabilities Equity Offering Costs In Accrued Liabilities Unrealized gain on marketable securities Marketable Securities, Unrealized Gain (Loss) Fair Value Measurement Inputs and Valuation Techniques [Table] Fair Value Measurement Inputs and Valuation Techniques [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Axis] Valuation Approach and Technique [Domain] Valuation Approach and Technique [Domain] Valuation Technique, Option Pricing Model Valuation Technique, Option Pricing Model [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Measurement Input Type [Axis] Measurement Input Type [Axis] Measurement Input Type [Domain] Measurement Input Type [Domain] Risk-free interest rate Measurement Input, Risk Free Interest Rate [Member] Expected life (in years) Measurement Input, Expected Term [Member] Expected volatility Measurement Input, Price Volatility [Member] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Fair Value Measurement Inputs and Valuation Techniques [Line Items] Warrants and rights outstanding, measurement input Warrants and Rights Outstanding, Measurement Input Warrants and rights outstanding, term Warrants and Rights Outstanding, Term Income Tax Contingency [Table] Income Tax Contingency [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] State and Local Jurisdiction State and Local Jurisdiction [Member] Domestic Tax Authority Domestic Tax Authority [Member] Income Tax Holiday [Line Items] Income Tax Contingency [Line Items] Unrecognized tax benefits Unrecognized Tax Benefits Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards Valuation allowance, 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Option [Member] 2017 PIPE 2017 PIPE [Member] 2017 PIPE [Member] Springer Purchase Agreement Springer Purchase Agreement [Member] Springer Purchase Agreement [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Common stock Common Stock [Member] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Class of warrant or right, outstanding (in shares) Class of Warrant or Right, Outstanding Warrant Issued Warrant Issued Warrant Issued Warrant, Down Round Feature, (Increase) Decrease in Equity, Amount Warrant, Down Round Feature, (Increase) Decrease in Equity, Amount Issuance costs Payments of Stock Issuance Costs Proceeds from issuance of common stock, net Proceeds From Issuance Of Common Stock, Net Proceeds From Issuance Of Common Stock, Net Shares issued, value Public securities offering, amount authorized Public Securities Offering, Amount Authorized Public Securities Offering, Amount Authorized Stock issued (in shares) Stock Issued During Period, Shares, New Issues Exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Share price (in dollars per share) Class of Warrant or Right, Issued to Purchase Common Stock Class of Warrant or Right, Issued to Purchase Common Stock Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Common stock, shares authorized (in shares) Common Stock, Shares Authorized Number of votes per share that common stockholders are entitled to Votes Per Share of Common Stock Votes Per Share of Common Stock Dividends declared or paid on common stock Dividends, Common Stock Net Loss Per Share Earnings Per Share [Text Block] Schedule of Property and Equipment Property, Plant and Equipment [Table Text Block] Shares available for future stock incentive awards Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected term Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Weighted-average fair value of common stock (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Fair Value Weighed-average fair value relating to the share-based payment award. Preferred stock, par value (in dollars 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, shares authorized Common stock, shares issued Common Stock, Shares, Issued Common stock, shares outstanding Common Stock, Shares, Outstanding Goodwill and Intangible Assets Disclosure [Abstract] Collaborative Arrangement and Arrangement Other than Collaborative [Table] Collaborative Arrangement and Arrangement Other than Collaborative [Table] 3SBio License License Agreement With Shenyang Sunshine Pharmaceutical Company Limited [Member] Represents information pertaining to License agreement with Shenyang Sunshine Pharmaceutical co., ltd. Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] Aggregate amount of upfront and milestone-based payments Aggregate Amount Of Upfront And Milestone Based Payments Paid Aggregate Amount Of Upfront And Milestone Based Payments Paid Aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for products containing ImmTOR platform Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Containing ImmTOR Platform Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Containing ImmTOR Platform Aggregate amount for future payments upon achievement of clinical and regulatory approval milestones for products without ImmTOR Platform Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Without ImmTOR Platform Aggregate Amount For Future Payments Upon Achievement Of Clinical And Regulatory Approval Milestones For Products Without ImmTOR Platform Principles of Consolidation Consolidation, Policy [Policy Text Block] Foreign Currency Foreign Currency Transactions and Translations Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Segment Information Segment Reporting, Policy [Policy Text Block] Cash Equivalents, Short-term Investments and Restricted Cash Cash Equivalents And Short Term Investments [Policy Text Block] Disclosure of accounting policy for cash equivalents and short term investments. Concentrations of Credit Risk and Off-Balance Sheet Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Impairment of Long-Lived Assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Debt Issuance Costs Debt, Policy [Policy Text Block] Accumulated Other Comprehensive Income (Loss) Comprehensive Income, Policy [Policy Text Block] Revenue Recognition Revenue from Contract with Customer [Policy Text Block] Research and Development Costs Research and Development Expense, Policy [Policy Text Block] Clinical Trial Costs Clinical Trial Costs [Policy Text Block] Disclosure of accounting policy for clinical trial costs. Income Taxes Income Tax, Policy [Policy Text Block] Warrants Warrants [Policy Text Block] Disclosure of accounting policy for warrants. Stock-Based Compensation Share-based Payment Arrangement [Policy Text Block] Net Loss Per Share Earnings Per Share, Policy [Policy Text Block] Contingent Liabilities Contingent Liability Reserve Estimate, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] MEE License Agreement With Massachusetts Eye And Ear Infirmary And Schepens Eye Research Institute Inc. [Member] Represents information pertaining to License agreement with Massachusetts Eye and Ear Infirmary and The Schepens Eye Research Institute, Inc. License fees due under agreement Initial License Fee Paid Initial License Fee Paid Schedule of Effective Income Tax Rate Reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Deferred Tax Assets and Liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Impairment of intangible assets, finite-lived Impairment of Intangible Assets, Finite-lived Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] TAS Partners, LLC (affiliate of Timothy A. Springer, Ph.D.) TAS Partners, LLC [Member] TAS Partners, LLC [Member] Carrie S. Cox Carrie S. Cox [Member] Carrie S. Cox [Member] Timothy Barabe Timothy Barabe [Member] Timothy Barabe [Member] Scott D. Myers Scott D. Myers [Member] Scott D. Myers [Member] Timothy A. Springer, Ph.D. Timothy A. Springer, Ph.D. [Member] Timothy A. Springer, Ph.D. [Member] Entities affiliated with Polaris Entities Affiliated With Polaris [Member] Entities Affiliated With Polaris [Member] Chafen Lu (Timothy A. Springer’s wife) Chafen Lu (Timothy Springer’s wife) [Member] Chafen Lu (Timothy Springer’s wife) [Member] Jed Springer (Timothy A. Springer’s brother) Jed Springer (Timothy Springer’s Brother) [Member] Jed Springer (Timothy Springer’s Brother) [Member] Elona Kogan, J.D. Elona Kogan, J.D. [Member] Elona Kogan, J.D. [Member] Patrick Zenner Patrick Zenner [Member] Patrick Zenner [Member] Takashi Kei Kishimoto, Ph.D. Takashi Kei Kishimoto, Ph.D. [Member] Takashi Kei Kishimoto, Ph.D. [Member] Carsten Brunn, Ph.D. Carsten Brunn, Ph.D. [Member] Carsten Brunn, Ph.D. [Member] Stephen Smolinski Stephen Smolinski [Member] Stephen Smolinski [Member] Stock issued (in shares) Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Furniture and fixtures Furniture and Fixtures [Member] Laboratory equipment, software and office equipment Equipment [Member] Computer equipment Computer Equipment [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Estimated useful life Property, Plant and Equipment, Useful Life Computation of Basic and Diluted Net Loss Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of Potential Common Shares Issuable Upon Conversion of Warrants Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Operating expenses Net (loss) income attributable to common stockholders - basic & diluted Net Income (Loss) Available to Common Stockholders, Basic Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Outstanding common stock options Share-based Payment Arrangement, Option [Member] Class of Stock [Line Items] Class of Stock [Line Items] Total (in shares) Deferred Tax Assets Deferred Tax Assets, Gross [Abstract] Stock-based compensations expense Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Deferred rent and other expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Deferred revenue Deferred Tax Assets, Deferred Income Operating lease liability Deferred Tax Assets, Operating Lease, Liability Deferred Tax Assets, Operating Lease, Liability Patent costs/amortization Deferred Tax Assets, Goodwill and Intangible Assets Gross deferred tax assets Deferred Tax Assets, Gross Deferred Tax Liabilities Deferred Tax Liabilities, Gross [Abstract] Depreciation Deferred Tax Liabilities, Property, Plant and Equipment Operating lease right-of-use asset Deferred Tax Liabilities, Operating Lease, Right-Of-Use Asset Deferred Tax Liabilities, Operating Lease, Right-Of-Use Asset Gross deferred tax liabilities Deferred Tax Liabilities, Gross Gross deferred tax liabilities Net deferred tax assets before valuation allowance Deferred Tax Assets, Net Of Deferred Tax Liabilities Deferred Tax Assets, Net Of Deferred Tax Liabilities Valuation allowance Deferred Tax Assets, Valuation Allowance Net deferred tax assets Deferred Tax Assets, Net Operating cash flows from operating leases Operating Lease, Payments Class of Warrant or Right [Table] Class of Warrant or Right [Table] Class of Warrant or Right [Axis] Class of Warrant or Right [Axis] Class of Warrant or Right [Domain] Class of Warrant or Right [Domain] Class of Warrant or Right [Line Items] Class of Warrant or Right [Line Items] Class of Warrant Or Right [Roll Forward] Class of Warrant Or Right [Roll Forward] Class of Warrant Or Right [Roll Forward] Class of warrant or right, outstanding, beginning balance (in shares) Issuance (in shares) Stock Issued During Period, Shares, Warrants Issued Stock Issued During Period, Shares, Warrants Issued Exercises (in shares) Stock Issued During Period Shares Warrants Exercised Number of warrants exercised during the current period. Expirations/ cancellations (in shares) Stock Issued During Period, Shares, Warrants Cancelled Stock Issued During Period, Shares, Warrants Cancelled Class of warrant or right, outstanding, ending balance (in shares) Exercise price, expirations / cancellations (in dollars per share) Warrant, Exercise Price, Decrease Exercise price, issuance (in dollars per share) Warrant, Exercise Price, Increase Income Taxes Income Tax Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Measurement Frequency [Domain] Measurement Frequency [Domain] Recurring Fair Value, Recurring [Member] Money market funds Money Market Funds [Member] (Level 1) Fair Value, Inputs, Level 1 [Member] (Level 2) Fair Value, Inputs, Level 2 [Member] (Level 3) Fair Value, Inputs, Level 3 [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] Assets: Assets, Fair Value Disclosure [Abstract] Cash and cash equivalents, fair value disclosure Cash and Cash Equivalents, Fair Value Disclosure Total Assets, Fair Value Disclosure Liabilities: Liabilities, Fair Value Disclosure [Abstract] Total Financial and Nonfinancial Liabilities, Fair Value Disclosure Schedule of Stockholders' Equity Note, Warrants or Rights Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block] Schedule of Authorized Shares of Common Stock for Future Issuance Schedule of Stock by Class [Table Text Block] Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Collaboration Agreements Collaboration And License Agreements [Text Block] Collaboration And License Agreements Employee awards Non‑employee awards Number of Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Beginning balance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Ending balance (in shares) Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Vested and expected to vest (in shares) Weighted-average exercise price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning balance (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Ending balance (in dollars per share) Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Weighted Average Exercise Price Vested and expected to vest (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Weighted-average remaining contractual term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term [Abstract] n/a Outstanding, term Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Vested, term Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Weighted Average Remaining Contractual Term Vested and expected to vest, term Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value [Abstract] n/a Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Vested Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Intrinsic Value Share-based Compensation Arrangement By Share-based Payment Award, Options, Vested, Outstanding, Intrinsic Value Vested and expected to vest Payroll and employee related expenses Employee-related Liabilities, Current Current portion of deferred rent and lease incentive Accrued Rent And Lease Incentive Payable Current " Carrying value as of the balance sheet date of obligations incurred through that date and payable for contractual rent under lease arrangements and 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 current portion of the liabilities (due within one year or within the normal operating cycle if longer)." Collaboration and licensing Accrued Collaboration and Licensing Accrued Collaboration and Licensing Accrued patent fees Accrued Patent Fees Current Carrying value as of the balance sheet date of patent fees. Accrued external research and development costs Accrued Research And Development Costs Current Carrying value as of the balance sheet date of research and development costs. Accrued professional and consulting services Accrued Audit Fees, Current Accrued Audit Fees, Current Accrued grant refund Accrued Grant Refund, Current Accrued Grant Refund, Current Accrued interest Interest Payable, Current Issuance costs, December financing Accumulated Amortization, Debt Issuance Costs, Current Other Other Accrued Liabilities, Current Accrued expenses Contractual payments defined in the Exclusive Patent License agreement License And Option Agreement, Contractual Payments Made License And Option Agreement, Contractual Payments Made Numerator: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Net loss attributable to common stockholders Denominator: Weighted‑average common shares outstanding—basic and diluted (in shares) Laboratory equipment Laboratory Equipment [Member] Represents information pertaining to laboratory equipment. Computer equipment and software Leasehold improvements Leasehold Improvements [Member] Office equipment Office Equipment [Member] Construction in process Construction in Progress [Member] Total property and equipment Property, Plant and Equipment, Gross Less accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property and equipment, net Restricted cash Restricted Cash and Cash Equivalents, Current Long-term restricted cash Restricted Cash and Cash Equivalents, Noncurrent Total cash, cash equivalents, and restricted cash shown in the consolidated statement of cash flows Year ended December 31, Long-term Debt, Fiscal Year Maturity [Abstract] 2020 Long-term Debt, Maturities, Repayments of Principal in Year Two 2021 Long-term Debt, Maturities, Repayments of Principal in Year Three 2022 Long-term Debt, Maturities, Repayments of Principal in Year Four Total minimum debt payments Long-term Debt Less: Amount representing interest Debt Instrument Interest Portion The interest portion of gross outstanding debt. Less: Debt discount and deferred charges Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net Less: Current portion of loan payable Long-term Debt, Current Maturities Loan payable, net of current portion Long-term Debt, Excluding Current Maturities Debt Debt Disclosure [Text Block] Fair Value Measurements Fair Value Disclosures [Text Block] Leases Lessee, Operating Leases [Text Block] Schedule of Quarterly Financial Information Quarterly Financial Information [Table Text Block] Accrued Expenses Accounts Payable, Accrued Liabilities, and Other Liabilities Disclosure, Current [Text Block] Subsequent Events [Abstract] Subsequent Events Subsequent Events [Text Block] Number of operating segments Number of Operating Segments Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Stock Options And Restricted Common Stock Stock Options And Restricted Common Stock [Member] Stock Options And Restricted Common Stock [Member] Research and development Research And Development [Member] Represents the information pertaining to research and development expenses included in the income statement. General and administrative General and Administrative Expense [Member] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Total stock-based compensation expense Statement of Stockholders' Equity [Abstract] Additional paid-In Capital Additional Paid-in Capital [Member] Stock option receivable Receivables from Stockholder [Member] Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning balance (in shares) Beginning balance Issuance of common stock under Employee Stock Purchase Plan (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Issuance of common stock under Employee Stock Purchase Plan Stock Issued During Period, Value, Employee Stock Purchase Plan Issuance of common stock upon exercise of options Stock Issued During Period, Value, Stock Options Exercised Stock‑based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Issuance of common stock, license agreement (in shares) Stock Issued During Period, Shares, Purchase of Assets Issuance of common stock, license agreement Issuance of common stock through private placement, net (in shares) Stock Issued During Period Value Conversion Preferred Stock Warrants, Shares Stock Issued During Period Value Conversion Preferred Stock Warrants, Shares Issuance of common stock through private placement, net of issuance costs of $37 Stock Issued During Period Value Conversion Preferred Stock Warrants The gross value of stock issued during the period upon the conversion of preferred stock warrants. Issuance of common stock, pre-funded warrants and warrants through private placement, net of issuance costs (in shares) Stock Issued During Period, Value, Pre-Funded Warrants And Warrants Through Private Placement, Shares Stock Issued During Period, Value, Pre-Funded Warrants And Warrants Through Private Placement, Shares Issuance of common stock, pre-funded warrants and warrants through private placement, net of issuance costs Stock Issued During Period, Value, Pre-Funded Warrants And Warrants Through Private Placement Stock Issued During Period, Value, Pre-Funded Warrants And Warrants Through Private Placement Currency translation adjustment Unrealized gains (losses) on securities Issuance of common stock, net of issuance costs (in shares) Issuance of common stock, net of issuance costs Issuance of common stock through at-the-market offering, net (in shares) Stock Issued During Period, Shares, Other Issuance of common stock through at-the-market offering, net Stock Issued During Period, Value, Other Issuance of restricted stock units (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Issuance of restricted stock units Stock Issued During Period, Value, Restricted Stock Award, Gross Adoption of new accounting principle Ending balance (in shares) Ending balance 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two Total future minimum lease payments Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Total operating lease liabilities Current operating lease liabilities Non-current operating lease liabilities Operating Lease, Liability, Noncurrent Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options to purchase common stock Stock warrants to purchase common stock Potential common shares Total (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Foreign currency translation adjustment Accumulated Foreign Currency Adjustment Attributable to Parent [Member] Unrealized gains (losses) on marketable securities AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] AOCI Attributable to Parent, Net of Tax AOCI Attributable to Parent, Net of Tax [Roll Forward] Other comprehensive income during the year Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent