Asset Acquisition [Abstract] Asset Acquisition [Abstract] Inception 4 Acquisition Asset Acquisition [Text Block] Asset Acquisition [Text Block] Quarterly Financial Information Disclosure [Abstract] Selected Quarterly Financial Information (unaudited) Quarterly Financial Information [Text Block] Share-based Payment Arrangement [Abstract] Cash proceeds from options exercised Proceeds from Stock Options Exercised Aggregate intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] 2013 Plan Stock Incentive2013 Plan [Member] Represents information pertaining to the 2013 Stock Incentive Plan. 2007 Plan Stock Incentive2007 Plan [Member] Represents information pertaining to the 2007 Stock Incentive Plan. 2019 Inducement Plan Two Thousand Nineteen Inducement Plan [Member] Two Thousand Nineteen Inducement Plan [Member] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Maximum Maximum [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Title of Individual [Axis] Title of Individual [Axis] Title of Individual [Domain] Title of Individual [Domain] Employees Employees [Member] Represents information pertaining to the employees. Consultants Consultants [Member] Represents information pertaining to the consultants. Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Stock options Share-based Payment Arrangement, Option [Member] ESPP Employee Stock [Member] Non-employee Options Nonemployee Stock Option [Member] An arrangement whereby an non-employees 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. Restricted stock units Restricted Stock [Member] Stock Option and Compensation Plans Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of shares reserved for issuance under the Plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Number of shares of common stock available for issuance under the Plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Annual increase in shares reserved for issuance under the Plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Annual Increase in Shares Reserved for Issuance Represents the number of shares which will annually increase the shares reserved for issuance under the equity-based compensation plan. Annual increase in shares reserved for issuance under the Plan (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Annual Increase in Shares Reserved for Issuance Represents the percentage of annual increase in the shares reserved for issuance under the equity-based compensation plan. Increase in number of shares available under the Plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized Purchase price of common stock as percentage of fair market value Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent Options outstanding (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Weighted-average exercise price of options (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 life of options Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Share-based compensation expense Share-based Payment Arrangement, Expense Unrecognized share-based compensation costs for option awards, net of estimated forfeitures Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount Expected weighted average period to recognize share-based compensation costs Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition RSUs expected to vest (in shares) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest The number of equity-based payment instruments, excluding stock (or unit) options, that are expected to vest in the future as of the reporting date. Weighted-average fair value of RSUs expected to vest (in dollars per share) Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest Weighted Average Grant Date Fair Value Represents the weighted average fair value of equity awards, other than options, that are expected to vest as of the reporting date. Aggregate intrinsic value of RSUs expected to vest Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Aggregate Intrinsic Value Expected To Vest Intrinsic value of equity-based compensation awards expected to vest. Excludes stock and unit options. Unrecognized compensation costs, net of estimated forfeitures Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Total fair value vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Common stock issued (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period Proceeds from stock plans Proceeds from Stock Plans Shares issued under ESPP (in shares) Stock Issued During Period, Shares, Employee Stock Purchase Plans Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] Schedule of Research and Development Arrangement, Contract to Perform for Others [Table] 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 Agreements License Agreement Terms [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Series A Preferred Stock Series A Preferred Stock [Member] Series B Preferred Stock Series B Preferred Stock [Member] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research and development Research and Development Expense [Member] General and administrative General and Administrative Expense [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] RHO-adRP License Agreement RHO-adRP License Agreement [Member] RHO-adRP License Agreement [Member] BEST1 License Agreement BEST1 License Agreement [Member] BEST1 License Agreement [Member] Licensing and Commercialization Agreement Licensing And Commercialization Agreement [Member] Represents information pertaining to the license and commercialization agreement entered into by the entity. Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Archemix Archemix Corp [Member] Represents information pertaining to Archemix Corp. University of Florida Research Foundation (UFRF) University of Florida Research Foundation (UFRF) [Member] University of Florida Research Foundation (UFRF) [Member] University Of Pennsylvania University Of Pennsylvania [Member] University Of Pennsylvania [Member] University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) [Member] University Of Florida Research Foundation (UFRF) And University Of Pennsylvania (Penn) [Member] University Of Massachusetts (UMass) University Of Massachusetts (UMass) [Member] University Of Massachusetts (UMass) [Member] Novartis Pharma AG Novartis Pharma A G [Member] Represents information pertaining to Novartis Pharma AG. Milestone Events [Axis] Milestone Events [Axis] Information pertaining to milestone events. Milestone Events [Domain] Milestone Events [Domain] Represents the types of milestone events. Achievement of specified clinical and regulatory milestones Achievement Of Specified Clinical And Regulatory Milestones [Member] Represents information pertaining to the achievement of specified clinical and regulatory milestones. First indication First Indication [Member] First Indication [Member] Second and third indication Second and Third Indication [Member] Second and Third Indication [Member] Sustained delivery applications Sustained Delivery Applications [Member] Sustained Delivery Applications [Member] Achievement of specified commercial milestones Achievement Of Specified Commercial Milestones [Member] Represents information pertaining to the achievement of specified commercial milestones. Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product [Member] Specified Clinical, Marketing Approval and Reimbursement Approval Milestones Related to a Licensed Product [Member] Specified Commercial Sales Milestones Related to a Licensed Product Specified Commercial Sales Milestones Related to a Licensed Product [Member] Specified Commercial Sales Milestones Related to a Licensed Product [Member] Achievement of specified patient enrollment milestones Achievement Of Specified Patient Enrollment Milestones [Member] Represents information pertaining to the achievement of specified patient enrollment milestones. Product and Service [Axis] Product and Service [Axis] Product and Service [Domain] Product and Service [Domain] C5 Licensed Product C5 Licensed Products [Member] Represents information pertaining to C5 Licensed products as defined by the agreement. Primary Licensed Product Primary Licensed Product [Member] Primary Licensed Product [Member] Other Licensed Product Other Licensed Product [Member] Other Licensed Product [Member] miniCEP290 miniCEP290 [Member] miniCEP290 [Member] License revenue Licensing [Member] Represents information pertaining to licensing activities. Research and development activity revenue Research And Development Activities [Member] Represents information pertaining to the research and development activities. API transfer revenue Active Pharmaceutical Ingredient Transfers [Member] Represents information pertaining to active pharmaceutical ingredient transfers. Joint operating committee revenue Joint Operating Committee Revenue [Member] Represents information pertaining to joint operating committee revenue. Agreement Research and Development Arrangement, Contract to Perform for Others [Line Items] Payments for license fees Payments For License Fees Payments for License Fees Shares issued for license fees (in shares) Shares Issued For License Fees Shares Issued For License Fees Amount to be paid on achievement of milestone Amount to be Paid On Achievement of Milestone Represents the amount to be paid by the entity on achievement of various milestones. Licensing agreement term Licensing Agreement Term Licensing Agreement Term Number of licensed products Number Of Licensed Products Number of Licensed Products Upfront fees received Research and Development Arrangement Upfront Fees Received Represents the amount of upfront fees received under the agreement. Patient enrollment-based milestone revenue achieved Research And Development Arrangement Amount Of Enrollment Based Milestone Achieved Represents the amount of patient enrollment-based milestone revenue achieved by the entity. Total collaboration revenue Revenues Accounting Policies [Abstract] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table] Share-Based Compensation Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Earnings Per Share [Abstract] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Stock options outstanding Employee And Nonemployee Stock Option [Member] An arrangement whereby an employee and non-employees are 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. Although there are variations, normally, after vesting, when an option is exercised, the holder pays the strike value in cash to the issuing employer-entity and receives equity shares. The equity shares can be sold into the market for cash at the current market price without restriction. Options may be used to attract, retain and incentivize employees, in addition to their regular salary and other benefits. Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Basis of Consolidation Consolidation, Policy [Policy Text Block] Segment and geographic information Segment Reporting, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Concentration of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Concentration of Suppliers Concentration of Suppliers Policy, [Policy Text Block] Disclosure of accounting policy for concentration of suppliers. Foreign Currency Translation Foreign Currency Transactions and Translations Policy [Policy Text Block] Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Leases Lessee, Leases [Policy Text Block] Property and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Research and Development Research and Development Expense, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Share-Based Compensation Share-based Payment Arrangement [Policy Text Block] Recently Adopted and Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Cash and Cash Equivalents [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Cash Cash Cash equivalents Cash Equivalents, at Carrying Value Available for sale debt securities Debt Securities, Available-for-sale Income Tax Disclosure [Abstract] Current: Current Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Current Federal Tax Expense (Benefit) State Current State and Local Tax Expense (Benefit) Deferred: Deferred Income Tax Expense (Benefit), Continuing Operations [Abstract] Federal Deferred Federal Income Tax Expense (Benefit) State Deferred State and Local Income Tax Expense (Benefit) Income tax benefit Income Tax Expense (Benefit) Property, Plant and Equipment [Abstract] Schedule of property and equipment Property, Plant and Equipment [Table Text Block] Schedule of computation of basic and diluted net income (loss) per common share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Schedule of potentially dilutive securities that have been excluded from the computations of diluted weighted average common shares outstanding Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Business Nature of Operations [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 (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding 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 Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Related Party Transactions [Abstract] Financing Agreement with Novo Holdings A/S Related Party Transactions Disclosure [Text Block] Net Income (Loss) Per Common Share Earnings Per Share [Text Block] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Novo A/S Novo [Member] Represents activity related to Novo A/S, a holding company and venture capital provider. Novo Agreement Royalty Agreement Terms [Member] Fovista, Fovista-Related Products, and Other Products Fovista And Related Products And Other Products [Member] Represents information pertaining to Fovista, Fovista-Related Products, and other products as defined by agreement. Number of tranches in financing Number Of Tranches In Financing The number of tranches in financing. Aggregate royalty rights Aggregate Royalty Guarantees Commitments Amount The amount the entity has committed to make for aggregate future royalty guarantees under agreement. Proceeds from royalty purchase agreement Proceeds from Other Debt Royalty purchase liability Royalty Guarantees, Commitments, Amount Gain on extinguishment of Royalty Purchase Liability Gain On Extinguishment Of Royalty Liability Gain On Extinguishment Of Royalty Liability Assets Assets [Abstract] Current assets Assets, Current [Abstract] Prepaid expenses and other current assets Prepaid Expense and Other Assets, Current Income tax receivable Income Taxes Receivable, Current Total current assets Assets, Current Property and equipment, net Property, Plant and Equipment, Net Right-of-use assets, net Operating Lease, Right-of-Use Asset Income tax receivable, non-current Income Taxes Receivable, Noncurrent Other assets Other Assets, Noncurrent Total assets Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Current liabilities Liabilities, Current [Abstract] Accrued research and development expenses Accrued Research and Development Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer) for research and development related activities. Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities, Current Lease liability, current Operating Lease, Liability, Current Total current liabilities Liabilities, Current Total liabilities Liabilities Stockholders' equity Stockholders' Equity Attributable to Parent [Abstract] Preferred stock—$0.001 par value, 5,000,000 shares authorized, no shares issued or outstanding Preferred Stock, Value, Issued Common stock—$0.001 par value, 200,000,000 shares authorized, 49,627,064 and 41,397,197 shares issued and outstanding at 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) Total stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Common Stock Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding at beginning of year (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) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Expired or forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Outstanding at end of year (in shares) Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Outstanding at beginning of year (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, 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 Expired or forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Outstanding at end of year (in dollars per share) Options exercisable at end of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted average grant date fair value (per share) of options granted during the period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Domestic Tax Authority Domestic Tax Authority [Member] State and Local Jurisdiction State and Local Jurisdiction [Member] Minimum Minimum [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Federal net operating loss carryforwards Operating Loss Carryforwards Income tax benefit Tax Cuts and Jobs Act, income tax expense Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit) Settlement of state franchise tax audit Tax Adjustments, Settlements, and Unusual Provisions Proceeds from income tax refunds Proceeds from Income Tax Refunds Income taxes receivable Income Taxes Receivable Reduction in deferred tax assets and corresponding valuation allowance Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Refund claimed for taxes previously paid Estimated Refund Adjustment from Settlement with Taxing Authority Estimated Refund Adjustment from Settlement with Taxing Authority Estimate of unrecognized tax benefits that may be realized over the next twelve months Significant Change in Unrecognized Tax Benefits is Reasonably Possible, Amount of Unrecorded Benefit Schedule of reconciliation of the statutory U.S. federal rate to the Company's effective tax rate Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of components of income tax (benefit) expense Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of significant components of the Company's deferred tax assets (liabilities) Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of position with respect to uncertain tax positions Summary of Income Tax Contingencies [Table Text Block] Leases [Abstract] Operating Leases Leases of Lessee Disclosure [Text Block] Income Taxes Income Tax Disclosure [Text Block] Schedule of weighted-average assumptions used to estimate grant date fair value of stock options Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of share-based compensation expense Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block] Research and development expenses Research and Development Expense General and administrative expenses General and Administrative Expense Income (loss) from operations Operating Income (Loss) Net income (loss) attributable to common stockholders Net Income (Loss) Available to Common Stockholders, Basic Basic (in dollars per share) Earnings Per Share, Basic Dilutive (in dollars per share) Earnings Per Share, Diluted Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Junior Series A Preferred Stock Junior Series A Convertible Preferred Stock [Member] Represents information pertaining to junior series A preferred stock that may be exchanged into common shares or other types of securities at the owner's option. Common Stock Common Stock [Member] Additional paid-in capital Additional Paid-in Capital [Member] Accumulated Deficit Retained Earnings [Member] Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Statement [Line Items] Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance at beginning of period (in shares) Shares, Issued Balance at beginning of period Issuance of common stock and pre-funded warrants, net (in shares) Stock Issued During Period, Shares, New Issues Issuance of common stock and pre-funded warrants through underwritten offering, net of issuance costs Stock Issued During Period, Value, New Issues Issuance of common stock related to acquisition (in shares) Stock Issued During Period, Shares, Acquisitions Issuance of common stock related to acquisition Stock Issued During Period, Value, Acquisitions Issuance of common stock under employee stock compensation plans and warrants (in shares) Stock Issued During Period Shares Options And Warrants Exercised Number of shares of stock issued as a result of the exercise of stock options and warrants. Issuance of common stock under employee stock compensation plans and warrants Stock Issued During Period Value Stock Options and Warrants Exercised Value of stock issued as a result of the exercise of stock options and warrants. Share-based compensation APIC, Share-based Payment Arrangement, Increase for Cost Recognition Net income Net Income (Loss) Attributable to Parent Unrealized gain on available for sale securities, net of tax Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax Balance at end of period (in shares) Ending balance Equity [Abstract] Common Stock Stockholders' Equity Note Disclosure [Text Block] Fair Value Disclosures [Abstract] 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 basis Fair Value, Recurring [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] Quoted prices in active markets for identical assets (Level 1) Fair Value, Inputs, Level 1 [Member] Significant other observable inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Significant unobservable inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instrument [Domain] Financial Instruments [Domain] Money market funds Money Market Funds [Member] Corporate debt securities Corporate Debt Securities [Member] Fair Value Measurements Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Investments in money market funds Cash and Cash Equivalents, Fair Value Disclosure Transfer of assets from Level 1 to Level 2 of the fair value measurement hierarchy Fair Value, Assets, Level 1 to Level 2 Transfers, Amount Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Expected common stock price volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Risk-free interest rate, minimum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum Risk-free interest rate, maximum Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum Expected term of options (years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Schedule Of Asset Acquisition [Table] Schedule Of Asset Acquisition [Table] Schedule Of Asset Acquisition [Table] GA GA Product [Member] GA Product [Member] Wet AMD Wet AMD Product [Member] Wet AMD Product [Member] Asset Acquisition [Axis] Asset Acquisition [Axis] Asset Acquisition [Axis] Asset Acquisition [Domain] Asset Acquisition [Domain] [Domain] for Asset Acquisition [Axis] Inception 4 Inception 4 [Member] Inception 4 [Member] Schedule Of Asset Acquisition [Line Items] Schedule Of Asset Acquisition [Line Items] [Line Items] for Schedule Of Asset Acquisition [Table] Number of shares issued in asset acquisition (in shares) Asset Acquisition, Equity Interest Issued Or Issuable, Number Of Shares Asset Acquisition, Equity Interest Issued Or Issuable, Number Of Shares Value of shares issued in asset acquisition Asset Acquisition, Consideration Transferred, Equity Interests Issued And Issuable Asset Acquisition, Consideration Transferred, Equity Interests Issued And Issuable Share price (USD per share) Share Price Contingent consideration Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Value, High Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Value, High Clinical and marketing approval milestones Asset Acquisition, Clinical And Marketing Approval Milestones Asset Acquisition, Clinical And Marketing Approval Milestones Contingently issuable shares, asset acquisition (in shares) Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Shares Issuable, High Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Shares Issuable, High Contingently issuable shares, asset acquisition, as a percentage of total shares outstanding Asset Acquisition, Contingent Consideration Arrangements, Contingently Issuable Shares As A Percentage Of Shares Outstanding Asset Acquisition, Contingent Consideration Arrangements, Contingently Issuable Shares As A Percentage Of Shares Outstanding Cash acquired in asset acquisition Asset Acquisition, Cash and Equivalents Asset Acquisition, Cash and Equivalents Non-cash charge on acquired in-process research and development Asset Impairment Charges Transaction costs Asset Acquisition, Transaction Costs Asset Acquisition, Transaction Costs Summary of the stock option activity including weighted average exercise prices, options outstanding and exercisable Share-based Payment Arrangement, Option, Activity [Table Text Block] Summary of the stock options outstanding and exercisable Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block] Schedule of cash proceeds from, and the aggregate intrinsic value of, stock options exercised Cash Proceeds Received and Tax Benefit from Share-based Payment Awards [Table Text Block] Summary of the Company's outstanding shares of RSU awards Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Restricted Stock Units Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Outstanding, beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Awarded (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Outstanding, end of period (in shares) 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 [Abstract] Outstanding, beginning of period (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 Awarded (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 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 dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding, end of period (in dollars per share) New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] ASU 2016-02 Accounting Standards Update 2016-02 [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Operating lease right-of-use asset Operating lease liability Operating Lease, Liability Weighted average estimated incremental borrowing rate Operating Lease, Weighted Average Discount Rate, Percent Operating lease rent expense Operating Lease, Expense Operating lease rent expense Operating Leases, Rent Expense, Net Cash paid from operating cash flows Operating Lease, Payments Operating lease, weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Operating right-of-use assets obtained in exchange for lease obligations Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Schedule of assets and liabilities that are measured at fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property and equipment Property, Plant and Equipment [Line Items] Estimated useful lives Property, Plant and Equipment, Useful Life Future minimum rental commitments under non-cancelable operating leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2020 Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months Total remaining obligation Lessee, Operating Lease, Liability, Payments, Due Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Present value of lease liabilities Retirement Benefits [Abstract] Defined contribution plan, cost recognized Defined Contribution Plan, Cost Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Deferred tax assets (liabilities) Components of Deferred Tax Assets and Liabilities [Abstract] License and technology payments Deferred Tax Assets License and Technology Payments Amount before allocation of valuation allowances of deferred tax asset attributable to deductible license and technology payments. Share-based compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Accrued expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals Right-of-use asset Deferred Tax Liabilities, Right-Of-Use Asset Deferred Tax Liabilities, Right-Of-Use Asset Lease obligation Deferred Tax Assets, Lease Obligation Deferred Tax Assets, Lease Obligation Depreciation Deferred Tax Liabilities, Property, Plant and Equipment Federal and state net operating loss carryforwards Deferred Tax Assets Operating Loss Carryforwards Federal State And Local Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards, including federal, state and local operating loss carryforwards. Research and development credits Deferred Tax Assets, Tax Credit Carryforwards, Research Other Deferred Tax Assets, Other Deferred income tax assets Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Net deferred tax assets Deferred Tax Assets, Net Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Share-based Payment Arrangement, Option, Exercise Price Range [Table] Share-based Payment Arrangement, Option, Exercise Price Range [Table] Exercise Price Range [Axis] Exercise Price Range [Axis] Exercise Price Range [Domain] Exercise Price Range [Domain] $1.13-$2.79 Exercise Price Range One [Member] Represents information pertaining to the exercise price range one. $2.80-$2.96 Exercise Price Range Two [Member] Represents information pertaining to the exercise price range two. $2.97-$4.87 Exercise Price Range Three [Member] Represents information pertaining to the exercise price range three. $4.88-$31.09 Exercise Price Range Four [Member] Represents information pertaining to the exercise price range four. $31.10-$73.22 Exercise Price Range Five [Member] Represents information pertaining to the exercise price range five. Range of Exercise Prices Share-based Payment Arrangement, Option, Exercise Price Range [Line Items] Exercise prices, low end of range (in dollars per share) Share-based Payment Arrangement, Option, Exercise Price Range, Lower Range Limit Exercise prices, high end of range (in dollars per share) Share-based Payment Arrangement, Option, Exercise Price Range, Upper Range Limit Options Outstanding Share Based Compensation, Shares Authorized under Stock Option Plans Exercise Price Range Options Outstanding [Abstract] Total Options Outstanding (in shares) Share-based Payment Arrangement, Option, Exercise Price Range, Shares Outstanding Weighted Average Remaining Life (Years) Share-based Payment Arrangement, Option, Exercise Price Range, Outstanding, Weighted Average Remaining Contractual Term Weighted Average Exercise Price (in dollars per share) Share-based Payment Arrangement, Option, Exercise Price Range, Outstanding, Weighted Average Exercise Price Aggregate Intrinsic Value of Options Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Options Exercisable Share Based Compensation Shares Authorized under Stock Option Plans Exercise Price Range Options Exercisable [Abstract] Number Exercisable (in shares) Share-based Payment Arrangement, Option, Exercise Price Range, Shares Exercisable Weighted Average Exercise Price (in dollars per share) Share-based Payment Arrangement, Option, Exercise Price Range, Exercisable, Weighted Average Exercise Price Aggregate Intrinsic Value of Options Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Schedule of Operating Lease Liability Maturities Lessee, Operating Lease, Liability, Maturity [Table Text Block] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Manufacturing and clinical equipment Equipment [Member] Computer, software and other office equipment Computer, Software, and Other Office Equipment [Member] Computer, Software, and Other Office Equipment [Member] Property and Equipment Useful life Property and equipment, gross Property, Plant and Equipment, Gross Accumulated depreciation Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Property and equipment, net Depreciation expense Depreciation Schedule of collaboration revenue components Collaborative Arrangement and Arrangement Other than Collaborative [Table Text Block] Employee Benefit Plan Pension and Other Postretirement Benefits Disclosure [Text Block] Cash and Cash Equivalents Cash and Cash Equivalents Disclosure [Text Block] Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Basic and diluted net loss per common share calculation: Earnings Per Share, Basic and Diluted [Abstract] Net income (loss) Weighted average common shares outstanding - basic (in shares) Weighted Average Number of Shares Outstanding, Basic Plus: net effect of dilutive stock options and unvested restricted stock units (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Weighted average common shares outstanding - dilutive (in shares) Weighted Average Number of Shares Outstanding, Diluted Net income (loss) per common share - basic (USD per share) Net income (loss) per common share - diluted (USD per share) Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Summary of the quarterly results of operations Quarterly Financial Information [Table Text Block] Stock-Based Compensation and Compensation Plans Share-based Payment Arrangement [Text Block] Income Statement [Abstract] Collaboration revenue Operating expenses: Operating Expenses [Abstract] Research and development General and administrative Total operating expenses Operating Expenses Income (loss) from operations Interest income Interest Income (Expense), Nonoperating, Net Other income (expense) Other Nonoperating Income (Expense) Income (loss) before income tax benefit Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax benefit Net income (loss) Net income (loss) per common share: Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Dilutive (in shares) Statement of Cash Flows [Abstract] Sale of Stock [Axis] Sale of Stock [Axis] Sale of Stock [Domain] Sale of Stock [Domain] Public Stock Offering Public Stock Offering [Member] Public Stock Offering [Member] Operating Activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Adjustments to reconcile net loss to net cash (used in) provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation Amortization of premium and discounts on investment securities Investment Income, Net, Amortization of Discount and Premium Non-cash charge on acquired in-process research and development Asset Impairment Charges, Excluding Transaction Costs Asset Impairment Charges, Excluding Transaction Costs Gain on sale of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Non-cash gain on extinguishment of royalty purchase agreement Deferred income taxes Deferred Income Taxes and Tax Credits Share-based compensation Share-based Payment Arrangement, Noncash Expense Stock-based consideration in connection with license acquisition Share-Based Payment Arrangement, Noncash Expense In Connection With License Acquisition Share-Based Payment Arrangement, Noncash Expense In Connection With License Acquisition Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Income tax receivable Increase (Decrease) in Income Taxes Receivable Due from Novartis Pharma AG Increase (Decrease) in Contract with Customer, Asset Prepaid expense and other assets Increase (Decrease) in Prepaid Expense and Other Current Assets The increase (decrease) during the reporting period in the value of prepaid expenses and other current assets not separately disclosed in the statement of cash flows. Accrued interest receivable Increase (Decrease) in Accrued Interest Receivable, Net Accrued research and development expenses Increase Decrease in Accrued research and development Represents the increase (decrease) during the reporting period in the aggregate amount of research and development expenses incurred. Accounts payable and accrued expenses Increase (Decrease) in Accounts Payable and Accrued Liabilities Deferred revenue Increase (Decrease) in Contract with Customer, Liability Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Purchase of marketable securities Payments to Acquire Marketable Securities Maturities of marketable securities Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Proceeds from sale of assets Proceeds from Sale of Productive Assets Net cash provided by investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Proceeds from issuance of common stock and pre-funded warrants, net Proceeds from Issuance of Common Stock Proceeds from employee stock plan purchases and stock option exercises Proceeds From Stock Options And Warrants Exercised The cash inflow from associated with the amount received from holders exercising their stock options and warrants. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Net change in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value [Abstract] Beginning of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents End of period Supplemental disclosure of cash paid Supplemental Disclosure of Cash Paid [Abstract] Income taxes received, net Income Taxes Paid, Net Supplemental disclosures of non-cash information related to investing activities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Change in unrealized gain (loss) on available for sale securities, net of tax Common stock issued to acquire net assets of Inception 4, Inc. Stock Issued Licensing and Commercialization Agreement Collaborative Arrangement Disclosure [Text Block] Percent of pre-tax income: Effective Income Tax Rate Reconciliation, Percent [Abstract] U.S. federal statutory income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent State 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 Remeasurement of deferred tax assets Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent Effective Income Tax Rate Reconciliation, Tax Cuts and Jobs Act, Percent Impact of state rate changes Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Research and development credit Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent Alternative minimum tax credit Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent Change in valuation allowance Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, Percent Schedule of Commitments and Contingencies [Table] Schedule of Commitments and Contingencies [Table] Schedule of information pertaining to commitments and contingencies. Commitments and contingencies Commitments and Contingencies [Line Items] Litigation settlement awared to other party Litigation Settlement, Amount Awarded to Other Party Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] Opening balance Unrecognized Tax Benefits Gross amount of increases in unrecognized tax benefits during the period - current year provisions Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions Gross amount of increases in unrecognized tax benefits during the period - prior year provisions Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions Gross amount of decreases in unrecognized tax benefits during the period - other Unrecognized Tax Benefits, Other Increase (Decrease) Unrecognized Tax Benefits, Other Increase (Decrease) Decreases due to settlement with tax authorities during the period Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities Reduction of unrecognized tax benefits due to expiration of the state of limitations during the period Unrecognized Tax Benefits, Reduction Resulting from Lapse of Applicable Statute of Limitations Closing Balance Document And Entity Information Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date 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 Emerging Growth Company Entity Emerging Growth Company Entity Small Business Entity Small Business Entity Shell Company Entity Shell Company Entity Filer Category Entity Filer Category Entity Public Float Entity Public Float Entity Common Stock, Shares Outstanding (in shares) Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Number of operating segments Number of Operating Segments Number of reporting segments Number of Reportable Segments Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Over-Allotment Option Over-Allotment Option [Member] Class of Stock [Line Items] Class of Stock [Line Items] Sale of stock, number of shares issued in transaction (in shares) Sale of Stock, Number of Shares Issued in Transaction Sale of stock, price per share (in dollars per share) Sale of Stock, Price Per Share Number of warrants issued (in shares) Class of Warrant or Right, Number of Securities Called by Warrants or Rights Warrant price (USD per share) Class of Warrant or Right, Exercise Price of Warrants or Rights Payments of stock issuance costs Payments of Stock Issuance Costs Payment of other stock issuance costs Payment Of Other Stock Issuance Costs Payment Of Other Stock Issuance Costs Sale of stock, consideration received on transaction Sale of Stock, Consideration Received on Transaction Shares issued for license agreement (in shares)