Document and Entity Information Statement [Table] Statement [Line Items] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Current Reporting Status Entity Filer Category Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Period Focus Condensed Consolidated Balance Sheets Assets [Abstract] ASSETS Assets, Current [Abstract] Current assets: Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents Marketable Securities, Current Marketable securities Receivables, Net, Current Accounts receivable Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Assets, Current Total current assets Property, Plant and Equipment, Net Property and equipment, net Property and equipment, net Other Assets, Noncurrent Restricted cash and other non-current assets Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities, Current [Abstract] Current liabilities: Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Total Notes Payable Notes payable Contract with Customer, Liability, Current Deferred revenue, current Other Liabilities, Current Other current liabilities Liabilities, Current Total current liabilities Contract with Customer, Liability, Noncurrent Deferred revenue, net of current portion Deferred revenue, long-term Capital Lease Obligations, Noncurrent Construction financing lease obligation, net of current portion Other Liabilities, Noncurrent Other non-current liabilities Liabilities Total liabilities Commitments and Contingencies. Commitments and contingencies (see note 7) Stockholders' Equity Attributable to Parent [Abstract] Stockholders’ equity Preferred Stock, Value, Issued Preferred stock, $0.0001 par value per share: 5,000,000 shares authorized; no shares issued or outstanding Common Stock, Value, Issued Common stock, $0.0001 par value per share: 195,000,000 shares authorized; 47,119,176 and 45,025,448 shares issued, and 46,711,695 and 44,507,960 shares outstanding at March 31, 2018 and December 31, 2017, respectively Additional Paid in Capital, Common Stock Additional paid-in capital Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss Retained Earnings (Accumulated Deficit) Accumulated deficit, Balance at End of Period Accumulated deficit, Balance at Beginning of Period Accumulated deficit Stockholders' Equity Attributable to Parent Total stockholders’ equity Liabilities and Equity Total liabilities and stockholders’ equity Preferred Stock, No Par Value Preferred stock, par value (in dollars 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 or Stated Value Per Share Common stock, par value (in dollars 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 Condensed Consolidated Statements of Operations Revenues Collaboration and other research and development revenues Operating Expenses [Abstract] Operating expenses: Research and Development Expense Research and development General and Administrative Expense General and administrative Operating Costs and Expenses Total operating expenses Operating Income (Loss) Operating loss Operating loss Nonoperating Income (Expense) [Abstract] Other income (expense), net: Other Nonoperating Income (Expense) Other income, net Investment Income, Net Interest income (expense), net Nonoperating Income (Expense) Total other income (expense), net Net Income (Loss) Attributable to Parent Net loss Net loss Net loss attributable to common stockholders Earnings Per Share, Basic and Diluted Net loss per share attributable to common stockholders, basic and diluted Weighted Average Number of Shares Outstanding, Basic and Diluted Weighted-average common shares outstanding, basic and diluted Condensed Consolidated Statements of Comprehensive Loss Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive loss: Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Unrealized loss on marketable debt securities Comprehensive Income (Loss), Net of Tax, Attributable to Parent Comprehensive loss Condensed Consolidated Statements of Cash Flows Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Cash flow from operating activities Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net loss Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash (used in) provided by operating activities: Share-based Compensation Stock-based compensation expense Depreciation Depreciation Research and Development in Process Non-cash research and development expense Other Noncash Income (Expense) Other non-cash items, net Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets Increase (Decrease) in Other Noncurrent Assets Other non-current assets Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses Amount of increase (decrease) in obligation to transfer good or service to customer for which consideration has been received or is receivable. Increase (Decrease) in Contract with Customer, Liability Deferred revenue Net Cash Provided by (Used in) Operating Activities Net cash (used in) provided by operating activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Cash flow from investing activities Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Proceeds from Sale of Machinery and Equipment Proceeds from the sale of equipment Payments to Acquire Marketable Securities Purchases of marketable securities Proceeds from Sale and Maturity of Marketable Securities Proceeds from maturities of marketable securities Net Cash Provided by (Used in) Investing Activities Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Cash flow from financing activities Proceeds from Issuance of Common Stock Proceeds from offering of common stock, net of issuance costs Repayments of Notes Payable Payments of notes payable Notes paid in cash Proceeds from Stock Options Exercised Proceeds from exercise of stock options Repayments of Debt and Capital Lease Obligations Payments on construction financing lease obligation Net Cash Provided by (Used in) Financing Activities Net cash provided by financing activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Net increase in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, cash equivalents and restricted cash, end of period Cash, cash equivalents and restricted cash, beginning of period Total Supplemental Cash Flow Information [Abstract] Supplemental disclosure of cash and non-cash activities: Capital Expenditures Incurred but Not yet Paid Fixed asset additions included in accounts payable and accrued expenses Amount of reclassification of liability for founder stock repurchase Reclassification of liability for common stock subject to repurchase Stock Issued Issuance of common stock for settlement of success payments Amount of adjustment to deferred revenue for adoption of accounting principle. Deferred Revenue Adjustment from Effect of New Accounting Principle Adjustment to deferred revenue for revenue adoption Future cash outflow to pay for stock issuance costs incurred. Initial public offering costs incurred but unpaid at period end Offering costs included in accounts payable and accrued expenses Nature of Business Nature of Operations [Text Block] Nature of Business Summary of Significant Accounting Policies Significant Accounting Policies [Text Block] Summary of Significant Accounting Policies Cash Equivalents & Marketable Securities Cash, Cash Equivalents, and Marketable Securities [Text Block] Cash Equivalents & Marketable Securities Fair Value Measurements Fair Value Disclosures [Text Block] Fair Value Measurements Accrued Expenses Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accrued Expenses Property and Equipment, net Property, Plant and Equipment Disclosure [Text Block] Property and Equipment, net Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies No definition available. Significant Agreements. Collaborative Arrangement Disclosure [Text Block] Significant Agreements Stock-based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-based Compensation Net Loss per Share Earnings Per Share [Text Block] Net Loss per Share Related-party Transactions Related Party Transactions Disclosure [Text Block] Related-party Transactions Subsequent Events Subsequent Events [Text Block] Subsequent Events Basis of Accounting, Policy [Policy Text Block] Unaudited Interim Financial Information Use of Estimates, Policy [Policy Text Block] Use of Estimates Disclosure of accounting policy for revenue from contract with customer. Revenue from Contract with Customer [Policy Text Block] Revenue Recognition New Accounting Pronouncements, Policy [Policy Text Block] Recent Accounting Pronouncements Schedule of Cash and Cash Equivalents [Table Text Block] Schedule of cash, cash equivalents, and restricted cash Contract with Customer, Asset and Liability [Table Text Block] Schedule of contract assets and liabilities Tabular disclosure of change in contract with customer asset and liability. Schedule of Change in Contract with Customer Asset and Liability [Table Text Block] Schedule of change in contract assets and contract liabilities Schedule of New Accounting Pronouncements and Changes in Accounting Principles [Table Text Block] Schedule of financial statement line items for comparability purposes Cash, Cash Equivalents and Investments [Table Text Block] Schedule of cash equivalents and marketable securities Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of assets measured at fair value on a recurring basis Schedule of Accrued Liabilities [Table Text Block] Schedule of accrued expenses Property, Plant and Equipment [Table Text Block] Schedule of property and equipment, net Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Schedule of stock-based compensation expense Nonvested Restricted Stock Shares Activity [Table Text Block] Schedule of changes in unvested restricted stock Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block] Schedule of stock option activity Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of assumptions used to value stock options Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Schedule of anti-dilutive common stock equivalents Subsidiary or Equity Method Investee, Sale of Stock by Subsidiary or Equity Investee [Table] Subsidiary, Sale of Stock [Line Items] Liquidity Stock Issued During Period, Shares, New Issues Number of common stock issued Proceeds from Issuance Initial Public Offering Aggregate net proceeds Cash and Cash Equivalents, at Carrying Value [Abstract] Cash, Cash Equivalents, and Restricted Cash Restricted Cash and Cash Equivalents, Noncurrent Restricted cash included in "Restricted cash and other non-current assets" Revenue, Initial Application Period Cumulative Effect Transition [Table] Revenue, Initial Application Period Cumulative Effect Transition [Line Items] Contract liabilities, deferred revenue: Contract with Customer, Liability Deferred revenue, Balance at End of Period Deferred revenue, Balance at Beginning of Period Deferred revenue Amount of additions in obligation to transfer good or service to customer for which consideration from customer has been received or is due. Contract with Customer Liability Additions Deferred revenue, Adjustments Accumulated deficit: Contracts Revenue Collaboration and other research and development revenues Total revenue Change in contract asset and contract liability balances Contract with Customer, Liability, Revenue Recognized Amounts included in the contract liability at the beginning of the period Restrictions on Cash and Cash Equivalents [Table] Restricted Cash and Cash Equivalents Items [Line Items] Cash equivalents and marketable securities Available-for-sale Debt Securities, Amortized Cost Basis Amortized Cost Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Gross Unrealized Losses Available-for-sale Securities, Debt Securities Fair Value Marketable securities Represents the number of available-for-sale securities that have been in a continuous unrealized loss position for less than twelve months. Number of Available for Sale Securities Held in Continuous Unrealized Loss Position Less Than Twelve Months Number of securities in an unrealized loss position Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months. Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Securities held by the Company in an unrealized loss position for less than 12 months Represents the number of available-for-sale securities that have been in a continuous unrealized loss position for twelve months or longer. Number of Available for Sale Securities Held in Continuous Unrealized Loss Position Twelve Months or Longer Number of securities in an unrealized loss position for more than 12 months Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). Debt Securities, Available-for-sale, Realized Gain (Loss) Realized gains (losses) on available-for-sale securities Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Assets, Fair Value Disclosure [Abstract] Financial Assets Cash and Cash Equivalents, Fair Value Disclosure Cash and cash equivalents Restricted Cash and Cash Equivalents Restricted cash Assets, Fair Value Disclosure Total financial assets The number of transfers between levels of the fair value hierarchy during the period. Transfers between levels Employee-related Liabilities, Current Employee related expenses Carrying value as of the balance sheet date of obligations incurred through that date and payable for fees associated with process and platform development. Process And Platform Development Costs Current Process and platform development expenses Carrying value as of the balance sheet date of obligations incurred through that date and payable for fees associated with intellectual property rights. Intellectual property and patent related fees Accrued Professional Fees, Current Professional service expenses Other Accrued Liabilities, Current Other expenses Carrying value as of the balance sheet date of obligations incurred through that date and payable for fees associated with Success payment. Success Payment Expenses, Current Success payment expenses Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Property and equipment disclosures Property, Plant and Equipment, Gross Total property and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: accumulated depreciation Schedule of Operating Leased Assets [Table] Operating Leased Assets [Line Items] Commitments and contingencies Area of leased space. Area of Leased Space Leased space ( in square feet) Security Deposit Security deposit Property, Plant and Equipment, Useful Life Estimated useful life Lessee Leasing Arrangements, Operating Leases, Renewal Term Extended lease option (in years) Operating Leases, Future Minimum Payments Receivable Future minimum rental revenue to be received Other Commitments [Table] Other Commitments [Line Items] Commitments and contingencies Professional and Contract Services Expense Expense for prosecution and maintenance of patent rights Amount of market capitalization. Market capitalization Market Capitalization Notes and Loans Payable [Abstract] Notes Payable Increase (Decrease) in Notes Payable, Current Promissory notes issued Debt Instrument, Interest Rate, Stated Percentage Interest rate (as a percentage) Stock Issued During Period, Shares, Issued for Services Common stock issued Stock issued to licensors The potential liability for company's sale success payments. Company Sale Success Payments, under Patent Rights Success Payments Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table] Significant Agreements. The number of research areas defined in the agreement. Number Of Research Areas Number of research areas The term of the research program under the agreement. Research Program Term Agreement term Number of collaboration development programs for the treatment of ocular disorders under the exclusive license from the company. Number of Collaboration Development Programs Number of Collaboration Development Programs Represents the number of members in the alliance steering committee (ASC) that was formed under the Allergan Agreement. Number Of Committee Members Number of Committee Members The number of extensions to the agreement permitted under the agreement. Agreement Extension Number Extensions The number of extensions to the agreement permitted under the agreement. Agreement Extension Period Extension period Proceeds from Collaborators Upfront fee received Represents the option exercise price during the Initial option period for each collaboration development program under the strategic alliance and option agreement. Collaboration Development Program Option Exercise Fee Under Strategic Alliance and Option Agreement Option exercise price per CDP Represents the Initial Option Period extension fee under the strategic alliance and option agreement. Collaboration Development Program Initial Option Period Extension Fee Under Strategic Alliance and Option Agreement Extension fee for Initial Option Period Represents the option exercise price for development and commercialization license after the Initial option period under the strategic alliance and option agreement. Collaboration Development Program Option Exercise Fee for Development and Commercialization Under Strategic Alliance and Option Agreement Option exercise price for development and commercialization license The aggregate potential liability for future clinical, regulatory and commercial milestone payments related to product approval. Potential Liability For Clinical Regulatory And Commercial Milestone Payments Potential liability for future clinical, regulatory and commercial milestone payments related to product approval The amount which the collaborator will pay to the reporting entity for research and development over the term of the agreement. Potential Cash Payments For Research And Development Funding Potential research and development funding The potential fee which the reporting entity could receive from the collaborator for each gene target identified under the Development and Commercialization License Potential Fee Receivable For Gene Targets Under Development And Commercialization License Potential fee receivable for each gene target licensed The number of additional development and Commercialization License that can be purchased. Number Of Additional Development And Commercialization License To Be Purchased Number of additional licenses The amount of one time payment to acquire the license. One Time Payment To Acquire License One time payment to acquire the license The potential fees which the reporting entity could receive for achievement of regulatory milestones. Potential Development Milestone Payments Potential development milestone payments The potential fees which the reporting entity could receive for achievement of regulatory and commercial milestones. Potential Regulatory and Commercial Milestone Payments Potential regulatory and commercial milestone payments The potential fees which the reporting entity could receive for achievement of regulatory milestones. Potential Regulatory Milestone Payments Potential regulatory milestone payments The potential fees which the reporting entity could receive for achievement of regulatory milestones. Potential Commercial Milestone Payments Potential commercial milestone payments Represents the milestone payment received under the license agreement. License Agreement Milestone Payment Received Milestone payment received under license agreement The amount of the next potential milestone payment which the reporting entity could receive. Amount Next Milestone Potential Payment Next possible milestone payment The portion of potential future consideration under the arrangement allocated to the R&D Services Unit of Accounting at the inception of the agreement. Allocable Arrangement Consideration Research And Development Services Unit Of Accounting Allocable arrangement consideration - R&D Services Unit of Accounting The portion of potential future consideration under the arrangement allocated to the Development and Commercialization License for the first research area at the inception of the agreement. Allocable Arrangement Consideration Development And Commercialization License Research Area1 Allocable arrangement consideration - Development and Commercialization License for the first research area The portion of potential future consideration under the arrangement allocated to the Development and Commercialization License for the second research area Allocable Arrangement Consideration Development And Commercialization License Research Area2 Allocable arrangement consideration - Development and Commercialization License for the second research area The portion of potential future consideration under the arrangement allocated to the Development and Commercialization License for the third research area at the inception of the agreement. Allocable Arrangement Consideration Development And Commercialization License Research Area3 Allocable arrangement consideration - Development and Commercialization License for the third research area The portion of potential future consideration under the arrangement allocated to the first Discount Deliverable (option to purchase gene target) for the first research area at the inception of the agreement. Allocable Arrangement Consideration First Discount Deliverable Research Area1 Allocable arrangement consideration - first Discount Deliverable for the first research area The portion of potential future consideration under the arrangement allocated to the second Discount Deliverable (option to purchase gene target) for the first research area at the inception of the agreement. Allocable Arrangement Consideration Second Discount Deliverable Research Area1 Allocable arrangement consideration - second Discount Deliverable for the first research area The portion of potential future consideration under the arrangement allocated to the third Discount Deliverable (option to purchase gene target) for the first research area at the inception of the agreement. Allocable Arrangement Consideration Third Discount Deliverable Research Area1 Allocable arrangement consideration - third Discount Deliverable for the first research area The portion of potential future consideration under the arrangement allocated to the first Discount Deliverable (option to purchase gene target) for the second research area at the inception of the agreement. Allocable Arrangement Consideration First Discount Deliverable Research Area2 Allocable arrangement consideration - first Discount Deliverable for the second research area The portion of potential future consideration under the arrangement allocated to the second Discount Deliverable (option to purchase gene target) for the second research area at the inception of the agreement. Allocable Arrangement Consideration Second Discount Deliverable Research Area2 Allocable arrangement consideration - second Discount Deliverable for the second research area The portion of potential future consideration under the arrangement allocated to the third Discount Deliverable (option to purchase gene target) for the second research area at the inception of the agreement. Allocable Arrangement Consideration Third Discount Deliverable Research Area2 Allocable arrangement consideration - third Discount Deliverable for the second research area The portion of potential future consideration under the arrangement allocated to the joint research program deliverable (JRC). Allocable Arrangement Consideration JRC Deliverable Allocable arrangement consideration -JRC Deliverable Represents the percentage of net revenue threshold for potential milestone payments to be made under the license agreement. License Agreement Percentage Threshold for Potential Milestone Payments Percentage of net sales threshold for potential milestone payments to be made Number of days in which the payment is to be made by the company on acceptance by the applicable regulatory authority of the Company’s submission of an IND application with respect to the LCA10 Program. Threshold Number of Days in Which Payment to be Made on Acceptance of Application Number of days in which payment to be made Represents the contract termination notice term under the license agreement. License Agreement Contract Termination Term Contract termination notice Disaggregation of Revenue Disaggregation of Revenue [Line Items] The amount of total transaction price. Revenue from Contract with Customer Transaction Price Total transaction price The amount of upfront non-refundable, non-creditable cash payment, million of research and development funding. Revenue from Contract with Customers Transaction Price Non Refundable Research and Development Payment Received Transaction price non refundable research and development funding The amount of transaction price milestone payment received. Revenue from Contract with Customer Transaction Price Milestone Payment Received Transaction price milestone payment received The amount of cash inflow from milestone payment received included in the transaction price. Revenue from Contract with Customers Milestone Payments Received Milestone payments received Represents upfront payment fees to collaborators under agreements. Payments for Upfront Fees To Collaborators Upfront fee Percentage of outstanding shares issued under collaboration agreement, which the reporting entity is obligated to maintain under the anti-dilution provisions of the agreement. Collaboration Agreement Percentage Outstanding Shares Issued Percentage of outstanding shares issued The potential liability for sales milestone payments. Potential Liability For Sales Milestones Potential liability for future sales milestone payments The aggregate potential liability for future clinical and regulatory milestone payments related to product approval. Potential Liability For Product Approval Clinical And Regulatory Milestone Payments Potential liability for future clinical and regulatory milestone payments related to product approval Represents the percentage of third party royalties that may be credited against the royalties due to counter party. Percentage of Royalties Paid Credited Towards Royalties Due Royalties credit paid to third party (as a percent) The number of licensed products, in a research and clinical milestones. Number of Licensed Products Number of licensed products Represents the market capitalization threshold under license agreement. Market Capitalization Threshold Market capitalization threshold Represents the payment terms for notes payable. Notes Payable Payment Terms Notes payable payment terms Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Stock-based compensation disclosures ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems Allocated Share-based Compensation Expense Compensation expense Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Changes in unvested restricted stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Unvested restricted common stock, end of period(in shares) Unvested restricted common stock, beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Balance, ending of period Balance, beginning of period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Changes in unvested stock options Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unrecognized stock-based compensation expense Number of share options exercised during the period, which had not yet fully vested. Stock Issued During Period Shares Stock Options Exercised Prior To Vesting Options exercised prior to vesting (in shares) The price per share at which options were exercised prior to their vesting. Stock Issued During Period Shares Stock Options Exercised Prior To Vesting Exercise Price Options exercised prior to vesting , exercise price per share Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Outstanding, end of period (in shares) Outstanding, beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Vested and expected to vest (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Exercisable (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Outstanding, end of period (in dollars per share) Outstanding, beginning of period (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Cancelled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Vested and expected to vest outstanding, weighted average exercise price (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Exercisable (in dollar per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Vested and expected to vest, remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Exercisable, remaining contractual life Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Vesting and expected to vest, aggregate intrinsic value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Exercisable, aggregated intrinsic value The number of shares of common stock held by the reporting entity which were issued for unvested stock options. Unvested Stock Held By Entity Unvested stock options (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted average fair value of options granted (per share) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Assumptions Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Risk free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Period for recognition Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Potentially dilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Anti-dilutive common stock equivalent shares Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Line Items] Related Party Transaction, Other Revenues from Transactions with Related Party Fees received from related party Sale of Stock [Axis] Sale Of Stock Name Of Transaction [Domain] Sale of Stock [Domain] I P O [Member] Initial Public Offering Follow-on offering sale of stock after the initial public offering to the public. Follow On Offering [Member] Follow-on Offering Public offering sale of stock after the initial public offering to the public. Public Offering [Member] Public Offering Initial Application Period Cumulative Effect Transition [Axis] Initial Application Period Cumulative Effect Transition [Domain] Initial Application Period Cumulative Effect Transition [Domain] Difference Between Revenue Guidance In Effect Before And After Topic606 [Member] Effect of Change Adjustments for New Accounting Pronouncements [Axis] Type Of Adoption [Member] Type of Adoption [Domain] Accounting Standards Update201409 [Member] ASU 2014-09 Calculated Under Revenue Guidance In Effect Before Topic606 [Member] As originally reported under Topic 606 Restricted Cash and Cash Equivalents [Axis] Restricted Cash And Cash Equivalents Cash And Cash Equivalents [Member] Cash and Cash Equivalents [Domain] Cash Equivalents [Member] Cash equivalents Money Market Funds [Member] Money market funds U S Treasury Securities [Member] U.S. Treasuries Financial Instrument [Axis] Transfers And Servicing Of Financial Instruments Types Of Financial Instruments [Domain] Financial Instruments [Domain] U S Government Agencies Debt Securities [Member] Government agency securities Measurement Frequency [Axis] Fair Value Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Fair Value Measurements Recurring [Member] Recurring Fair Value, Hierarchy [Axis] Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value Inputs Level1 [Member] Level 1 Property, Plant and Equipment, Type [Axis] Property Plant And Equipment Type [Domain] Property, Plant and Equipment, Type [Domain] Building [Member] Building Laboratory equipment used for research and development. Laboratory Equipment [Member] Laboratory equipment Computer Equipment [Member] Computer equipment Leasehold Improvements [Member] Leasehold improvements Software And Software Development Costs [Member] Software Furniture And Fixtures [Member] Furniture and office equipment Lease Arrangement, Type [Axis] Lease Arrangement Type [Domain] Lease Arrangement, Type [Domain] Lease agreement of office and laboratory space located in Cambridge, Massachusetts. Hurley Street Lease [Member] Hurley Street Lease Facility sublease arrangement. Facility Sublease Arrangement [Member] Facility Sublease Arrangement Other Commitments [Axis] Other Commitments [Domain] Other Commitments [Domain] Commitment to reimburse the licensor for prosecution and maintenance of patent rights pursuant to the license agreement by and among the reporting entity, The Broad Institute Inc. and the Fellows of Harvard College. Commitment To Reimburse Licensor [Member] Licensor Expense Reimbursement Type of Arrangement and Non-arrangement Transactions [Axis] Arrangements And Nonarrangement Transactions [Member] Arrangements and Non-arrangement Transactions [Domain] Represents the patent license agreements with each of The General Hospital Corporation, d/b/a Massachusetts General Hospital (“MGH”) and Broad (collectively, the “2016 License Agreements”). License Agreements2016 [Member] 2016 License Agreements Represents a license agreement, the Cpf1 License Agreement, with Broad, for specified patent rights (the “Cpf1 Patent Rights”) related primarily to Cpf1 compositions of matter and their use for gene editing. Cpf1 License Agreement [Member] Cpf1 License Agreement Counterparty Name [Axis] Repurchase Agreement Counterparty Name [Domain] Counterparty Name [Domain] Represents information related to Broad and Wageningen University. Broad And Wageningen University [Member] Broad and Wageningen University Represents information pertaining to The Broad Institute Inc. Broad Institute Inc [Member] The Broad Institute Inc Represents information pertaining to Wageningen University. Wageningen University [Member] Wageningen University The General Hospital corporation, doing business as Massachusetts General Hospital. General Hospital Corporation [Member] The General Hospital (MGH) Short-term Debt, Type [Axis] Short Term Debt Type [Domain] Short-term Debt, Type [Domain] Represents information pertaining to Success payment notes. Success Payment Notes [Member] Success Payment Notes Range [Axis] Range [Member] Range [Domain] Maximum [Member] Maximum Collaboration and license agreement. Collaboration And License Agreement [Member] Collaboration and License Agreement Represents information pertaining to strategic alliance. Strategic Alliance [Member] Strategic Alliance Juno Therapeutics. Juno Therapeutics [Member] Juno Therapeutics Represents information pertaining to Allergan. Allergan [Member] Allergan Harvard College, the Broad Institute and Massachusetts Institute of Technology. Harvard Broad Mit [Member] Broad, Massachusetts Institute of Technology, or MIT, and Harvard (Institutions) Geographical [Axis] Segment Geographical [Domain] Geographical [Domain] The geographical area covered by the United States, the European Union, and Japan. United States Europe And Japan [Member] United States Europe And Japan Two geographical areas, one of which is the United States. United States And One Other Location [Member] United States and one other U [S] UNITED STATES Products and Services [Axis] Products And Services [Domain] Products and Services [Domain] Product for treatment of human disease. Product For Treatment Of Human Disease [Member] Human disease Product for treatment of rare disease. Product For Treatment Of Rare Disease [Member] Rare disease License of patent rights. License Patent Rights [Member] License Patent Rights Represents the success payments in the event the Company’s market capitalization reaches specified thresholds (the “Cpf1 Market Cap Success Payments”) or a Company sale for consideration in excess of those thresholds (the “Cpf1 Company Sale Success Payments” and, collectively with the Cpf1 Market Cap Success Payments, the “Cpf1 Success Payments”). Cpf1 Success Payments [Member] Cpf1 Success Payments Represents the success payments in the event the Company’s market capitalization reaches specified thresholds (the “Cpf1 Market Cap Success Payments”). Cpf1 Market Cap Success Payments [Member] Cpf1 Market Cap Success Payments Represents a license agreement, the Cas9-II License Agreement, Broad, on behalf of itself, MIT, Harvard, and the University of Iowa Research Foundation, granted the Company an exclusive, worldwide, royalty bearing sub licensable license to certain of the Cas9 II Patent Rights as well as a non exclusive, worldwide, royalty bearing sub licensable license to all of the Cas9 II Patent Rights. Cas9 I I License Agreement [Member] Cas9-II License Agreement Minimum [Member] Minimum Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research And Development Expense [Member] Research and development. General And Administrative Expense [Member] General and administrative Award Type [Axis] Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Equity Award [Domain] Restricted Stock [Member] Restricted Stock Title of Individual [Axis] Title Of Individual With Relationship To Entity [Domain] Relationship to Entity [Domain] Employees and directors. Employee And Director [Member] Employees and directors Persons hired to provide services to a company on a regular basis in exchange for compensation. Employee [Member] Employees Non-employees. Non Employee [Member] Non-employees Antidilutive Securities [Axis] Antidilutive Securities Name [Domain] Antidilutive Securities, Name [Domain] Employee Stock Option [Member] Outstanding stock options Convertible Debt Securities [Member] Convertible notes Related Party Transaction [Axis] Related Party Transaction [Domain] Related Party Transaction [Domain] Represents the rent and facility related fees paid to the related parties. Rent And Facility Related Fees [Member] Rent and facility related fees