Accounting Policies [Abstract] Impairment of intangible assets, finite-lived Impairment of Intangible Assets, Finite-lived Retirement Benefits [Abstract] 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. 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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] Goodwill and Intangible Assets Disclosure [Abstract] Collaboration and License Agreements Collaboration And License Agreements [Text Block] Collaboration And License Agreements Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research and development Research And Development [Member] Represents the information pertaining to research and development expenses included in the income statement. 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Springer, Ph.D. Timothy A. Springer, Ph.D. [Member] Timothy A. Springer, Ph.D. [Member] Entities affiliated with NanoDimension Entities Affiliated With NanoDimension [Member] Entities Affiliated With NanoDimension [Member] Entities affiliated with OrbiMed Advisors Entities Affiliated With OrbiMed Advisors [Member] Entities Affiliated With OrbiMed Advisors [Member] Entities affiliated with Polaris Entities Affiliated With Polaris [Member] Entities Affiliated With Polaris [Member] SAF-BND Trust (affiliate of Omid Farokhzad, M.D.) SAF-BND Trust (affiliate of Omid Farokhzad, M.D.) [Member] SAF-BND Trust (affiliate of Omid Farokhzad, M.D.) [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] TAS Partners, LLC (affiliate of Timothy A. Springer, Ph.D. TAS Partners, LLC [Member] TAS Partners, LLC [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] Scott D. Myers Scott D. Myers [Member] Scott D. Myers [Member] Stephen Smolinski Stephen Smolinski [Member] Stephen Smolinski [Member] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Director Director [Member] Related Party Transaction [Line Items] Related Party Transaction [Line Items] Stock issued (in shares) Sale of Stock, Number of Shares Issued in Transaction Shares issued, value Proceeds from Issuance of Common Stock Statement of Stockholders' Equity [Abstract] Issuance costs Payments of Stock Issuance Costs Employee stock option grants Share-based Payment Arrangement [Member] 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. 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. Unvested restricted stock units Restricted Stock Units (RSUs) [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. 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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 Grants in period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Reserved for issuance (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease) 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 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 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 Weighted average period for recognition Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross 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 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Stock‑based compensation expense Shares issued (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 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 Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Earnings Per Share [Abstract] 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) Property, Plant and Equipment [Abstract] Depreciation expense Depreciation Number of operating segments Number of Operating Segments Revenue from Contract with Customer [Abstract] Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Restatement [Axis] Restatement [Axis] Restatement [Domain] Restatement [Domain] Restatement Adjustment Restatement Adjustment [Member] Adjustments for Error Corrections [Axis] Adjustments for Error Corrections [Axis] Adjustments for Error Correction [Domain] Adjustments for Error Correction [Domain] Error Recognized Upon the Initial Adoption of ASC 606 Error Recognized Upon the Initial Adoption of ASC 606 [Member] Error Recognized Upon the Initial Adoption of ASC 606 [Member] Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] Grant Revenue Grant [Member] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Accumulated deficit Retained Earnings [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2014-09 Accounting Standards Update 2014-09 [Member] 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] 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 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] 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] License and Supply Obligation License And Supply Obligation [Member] License And Supply Obligation [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] Upfront cash payment License And Option Agreement, Upfront Cash Payment License And Option Agreement, Upfront Cash Payment 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 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 Contract with Customer, Liability Deferred revenue, current portion Contract with Customer, Liability, Current Deferred revenue, net of current portion Contract with Customer, Liability, Noncurrent 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 Remaining performance obligation Revenue, Remaining Performance Obligation, Amount Performance obligation per each option Revenue, Remaining Performance Obligation, Each Option Revenue, Remaining Performance Obligation, Each Option Incremental costs of obtaining a contract Capitalized Contract Cost, Net Percentage of sublicense income Percentage Of Sublicense Income Represents information pertaining to percentage of sublicense income. Current assets Assets, Current Long-term assets Assets, Noncurrent Revenue recognized Contract with Customer, Liability, Deferred Revenue, Revenue Recognized Contract with Customer, Liability, Deferred Revenue, 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. 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[Text Block] Nature of the Business and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] 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) Stock-based compensation expense 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] 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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 Investments, Debt and Equity Securities [Abstract] Available-for-Sale Marketable Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Defined Contribution Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Statement of Financial Position [Abstract] 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, par value (in dollars 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 Revenue Arrangements Revenue from Contract with Customer [Text Block] Schedule of Changes in Contract Liabilities Contract with Customer, Asset and Liability [Table Text Block] Leases Lessee, Operating Leases [Text Block] Operating cash flows from operating leases Operating Lease, Payments Schedule of Future Minimum Payments on the Term Loans Schedule of Maturities of Long-term Debt [Table Text Block] 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 Stock Incentive Plans Share-based Payment Arrangement [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 Fair Value Measurements Fair Value Disclosures [Text Block] Contractual payments defined in the Exclusive Patent License agreement License And Option Agreement, Contractual Payments Made License And Option Agreement, Contractual Payments Made Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive 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and Equipment [Line Items] Property, Plant and Equipment [Line Items] Estimated useful life Property, Plant and Equipment, Useful Life Statement of Cash Flows [Abstract] Statement [Table] Statement [Table] At-The-Market Offering At-The-Market Offering [Member] At-The-Market Offering [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 (Gain) loss 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 Net realized losses on investments Realized Investment Gains (Losses) Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] 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 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] Repayments of principal on outstanding debt Repayments of Long-term Debt Net 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 Unrealized gain (loss) on marketable securities Marketable Securities, Unrealized Gain (Loss) Schedule of Property and Equipment Property, Plant and Equipment [Table Text Block] 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 Property, Plant and Equipment, Net Schedule of Related Party Transactions Schedule of Related Party Transactions [Table Text Block] Property and Equipment Property, Plant and Equipment Disclosure [Text Block] 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] 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 Exercised (in shares) Forfeited (in shares) 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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number 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 Schedule of Accrued Expenses Schedule of Accrued Liabilities [Table Text Block] 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 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) 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) Common stock Common Stock [Member] 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 Stockholders' Equity Attributable to Parent 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 Issuance of common stock, net of issuance costs (in shares) Stock Issued During Period, Shares, New Issues Issuance of common stock, net of issuance costs of $344 Stock‑based compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Currency translation adjustment Unrealized gains (losses) on securities 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 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. Adoption of new accounting principle Ending balance (in shares) Ending balance Cover page. Document Type Document Type Document Quarterly Report Document Quarterly 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 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 Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding 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 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 Accrued license fees Accrued Professional Fees 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] Title of Individual [Axis] Title of Individual [Axis] Title of Individual [Domain] Title of Individual [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, 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 Consulting services expenses Related Party Transaction, Expenses from Transactions with Related Party 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 available-for-sale 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 (loss) during the period Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Exercise of common warrants Shares available for future stock incentive awards Outstanding common stock options Class of Stock [Line Items] Class of Stock [Line Items] Total (in shares) Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Public Stock Offering Public Stock Offering [Member] Public Stock Offering [Member] Over-Allotment Option Over-Allotment Option [Member] 2017 PIPE 2017 PIPE [Member] 2017 PIPE [Member] Springer Purchase Agreement Springer Purchase Agreement [Member] Springer Purchase Agreement [Member] IPO IPO [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Subsidiary, Sale of Stock [Line Items] Subsidiary, Sale of Stock [Line Items] Proceeds from issuance of common stock, net Proceeds From Issuance Of Common Stock, Net Proceeds From Issuance Of Common Stock, Net Public securities offering, amount authorized Public Securities Offering, Amount Authorized Public Securities Offering, Amount Authorized Stock issued (in shares) Exercise price (in dollars per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Warrants and rights outstanding, term Warrants and Rights Outstanding, Term 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 Proceeds from Initial Public Offering, net of underwriters' discounts and commissions Proceeds from Issuance Initial Public Offering Convertible preferred stock, shares issued upon conversion (in shares) Convertible Preferred Stock, Shares Issued upon Conversion Common stock, shares authorized (in shares) 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 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] Term loan facility Long-term Line of Credit Repayments of debt Repayments of Lines of Credit Loss on extinguishment of debt Gain (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 Assets Assets [Abstract] Current assets: Assets, Current [Abstract] Cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Current Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Current Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Total current assets Property and equipment, net Right of use asset, net (Note 8) 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, current portion Loans Payable, Current Lease liability, current portion (Note 8) Total current liabilities Liabilities, Current Non‑current liabilities: Other Liabilities, Noncurrent [Abstract] Deferred rent and lease incentive Deferred Rent Credit, Noncurrent 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 September 30, 2019 and December 31, 2018, respectively Preferred Stock, Value, Issued Common stock, $0.0001 par value; 200,000,000 shares authorized; 48,196,387 and 22,471,776 shares issued and outstanding as of September 30, 2019 and December 31, 2018, respectively Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital Accumulated deficit Accumulated other comprehensive loss Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity (deficit) Total liabilities and stockholders’ equity (deficit) Liabilities and Equity Net Loss Per Share Earnings Per Share [Text Block] 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 Other Other Accrued Liabilities, Current Accrued expenses Schedule of Operating Leased Assets [Table] Schedule of Operating Leased Assets [Table] Accounting Standards Update 2016-02 Accounting Standards Update 2016-02 [Member] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Laboratory and office space Laboratory And Office Space [Member] Represents information pertaining to laboratory and office space member. Letter of credit Letter of Credit [Member] 75 North Beacon, Watertown, MA 75 North Beacon, Watertown, MA [Member] 75 North Beacon, Watertown, MA [Member] Operating Leased Assets [Line Items] Operating Leased Assets [Line Items] Right of use asset, net Lease liabilities 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 Operating lease, expense Operating Lease, Expense Lessee, Operating Lease, Liability, Payments, Due Debt Debt Disclosure [Text Block]