Statement of Financial Position [Abstract] Assets Assets [Abstract] Current assets Assets, Current [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value 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 Deferred tax assets Deferred Income Tax Assets, Net 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 Total current liabilities Liabilities, Current Royalty purchase liability Royalty Guarantees, Commitments, Amount 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, 36,188,161 and 36,110,298 shares issued and outstanding at June 30, 2018 and December 31, 2017, 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 Statement of Comprehensive Income [Abstract] Net loss Net Income (Loss) Attributable to Parent Other comprehensive loss: Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Unrealized gain on available for sale securities, net of tax Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Disclosure of Compensation Related Costs, Share-based Payments [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 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 Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Restructuring and Related Activities [Abstract] Schedule of severance costs Restructuring and Related Costs [Table Text Block] Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] 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] Restructuring Type [Axis] Restructuring Type [Axis] Type of Restructuring [Domain] Type of Restructuring [Domain] Accrued Severance and Other Employee Costs Employee Severance [Member] Restructuring Cost and Reserve [Line Items] Restructuring Cost and Reserve [Line Items] Severance, stock compensation and other employee costs Severance Costs Restructuring Reserve [Roll Forward] Restructuring Reserve [Roll Forward] Beginning Balance Restructuring Reserve Accrued restructuring expenses Restructuring Charges Payments Payments for Restructuring Ending Balance Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring basis Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [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] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [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 Investments in investment-grade corporate debt securities Available-for-sale Securities, Debt Securities 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 Number of Shares Underlying 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 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 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 Cash, Cash Equivalents, and Short-term Investments [Abstract] Cash, Cash Equivalents and Available for Sale Securities Cash, Cash Equivalents, and Short-term Investments [Text Block] Property, Plant and Equipment [Abstract] Schedule of property and equipment Property, Plant and Equipment [Table Text Block] Accounting Policies [Abstract] Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] ESPP Employee Stock [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Maximum Maximum [Member] Share-Based Compensation Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [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 Share-based compensation expense Allocated Share-based Compensation Expense Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Minimum Minimum [Member] Property and equipment Property, Plant and Equipment [Line Items] Estimated useful lives Property, Plant and Equipment, Useful Life Basis of Presentation Basis of Accounting, 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] Available for Sale Securities Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block] Revenue Recognition Revenue Recognition, 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] 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 Compensation, Option and Incentive Plans Policy [Policy Text Block] Recently Adopted and Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Stock Option and Compensation Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] 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. Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Employees Employees [Member] Represents information pertaining to the employees. Consultants Consultants [Member] Represents information pertaining to the consultants. Stock options Employee Stock Option [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 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 Aggregate intrinsic value of options outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Unrecognized share-based compensation costs for option awards, net of estimated forfeitures Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options Expected weighted average period to recognize share-based compensation costs Employee Service Share-based Compensation, Nonvested Awards, Compensation 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 Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options 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 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 Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Schedule of Commitments and Contingencies [Table] Schedule of Commitments and Contingencies [Table] Schedule of information pertaining to commitments and contingencies. 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] Type of Arrangement and Non-arrangement Transactions [Axis] Type of Arrangement and Non-arrangement Transactions [Axis] Arrangements and Non-arrangement Transactions [Domain] Arrangements and Non-arrangement Transactions [Domain] License Agreements License Agreement Terms [Member] 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] Products and Services [Axis] Products and Services [Axis] Products and Services [Domain] Products and Services [Domain] C5 Licensed Product C5 Licensed Products [Member] Represents information pertaining to C5 Licensed products as defined by the agreement. 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 with respect 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 with respect to a licensed product Specified Commercial Sales Milestones Related to a Licensed Product [Member] Specified Commercial Sales Milestones Related to a Licensed Product [Member] Commitments and contingencies Commitments and Contingencies [Line Items] 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. Property and Equipment Property, Plant and Equipment Disclosure [Text Block] Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Related Party Transactions [Abstract] Financing Agreement with Novo A/S Related Party Transactions Disclosure [Text Block] Restructuring Activities Restructuring and Related Activities Disclosure [Text Block] Fair Value Measurements Fair Value, Measurement Inputs, Disclosure [Text Block] Statement of Cash Flows [Abstract] Operating Activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Net loss Adjustments to reconcile net loss to net cash used in operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation Depreciation Amortization of premium and discounts on investment securities Investment Income, Net, Amortization of Discount and Premium Deferred income taxes Deferred Income Taxes and Tax Credits Share-based compensation Share-based Compensation Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Due from Novartis Pharma AG Increase (Decrease) in Contract Receivables, Net Income tax receivable Increase (Decrease) in Income Taxes Receivable Prepaid expense and other current 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 Other assets Increase (Decrease) in Other Noncurrent Assets 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 Deferred Revenue 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 Available-for-sale Securities 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 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 and Cash Equivalents, Period Increase (Decrease) Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value [Abstract] Beginning of period End of period Supplemental disclosure of cash paid Supplemental Disclosure of Cash Paid [Abstract] Income tax refunds received 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 loss on available for sale securities, net of tax Available-for-sale Securities, Change in Net Unrealized Holding Gain (Loss), Net of Tax Earnings Per Share [Abstract] 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] 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 Number of operating segments Number of Operating Segments Number of reporting segments Number of Reportable Segments Summary of the stock option activity including weighted average exercise prices, options outstanding and exercisable Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of the stock options outstanding and exercisable Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by 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] One Penn Plaza LLC One Penn Plaza LLC [Member] One Penn Plaza LLC [Member] Otsuka America Pharmaceutical, Inc. Otsuka America Pharmaceutical, Inc. [Member] Otsuka America Pharmaceutical, Inc. [Member] Lease Termination Contract Termination [Member] Percent of personnel expected to be effected by reduction in workforce Restructuring and Related Cost, Number of Positions Eliminated, Inception to Date Percent Accrual balance for severance and benefit costs Early termination payment Basic and diluted net loss per common share calculation Earnings Per Share, Basic and Diluted [Abstract] Weighted average common shares outstanding - basic and dilutive (in shares) Weighted Average Number of Shares Outstanding, Basic and Diluted Net loss per common shares - basic and diluted (in dollars per share) Earnings Per Share, Basic and Diluted 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. Anti-dilutive securities Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Total (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, 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 Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table] Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table] Exercise Price Range [Axis] Exercise Price Range [Axis] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain] $0.12-$10.03 Exercise Price Range One [Member] Represents information pertaining to the exercise price range one. $10.04-$20.00 Exercise Price Range Two [Member] Represents information pertaining to the exercise price range two. $20.01-$30.00 Exercise Price Range Three [Member] Represents information pertaining to the exercise price range three. $30.01-$40.00 Exercise Price Range Four [Member] Represents information pertaining to the exercise price range four. $40.01-$55.00 Exercise Price Range Five [Member] Represents information pertaining to the exercise price range five. $55.01-$73.22 Exercise Price Range Six [Member] Represents information pertaining to the exercise price range six. Range of Exercise Prices Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items] Options Outstanding Share Based Compensation, Shares Authorized under Stock Option Plans Exercise Price Range Options Outstanding [Abstract] Total Shares Underlying Options Outstanding (in shares) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options Weighted Average Remaining Life (Years) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term Weighted Average Exercise Price (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, 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 of Shares for which Options are Exercisable (in shares) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options Weighted Average Exercise Price (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price Aggregate Intrinsic Value of Options Exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Exercise prices, low end of range (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Exercise prices, high end of range (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] 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] Achievement of specified patient enrollment milestones Achievement Of Specified Patient Enrollment Milestones [Member] Represents information pertaining to the achievement of specified patient enrollment milestones. Novartis Pharma AG Novartis Pharma A G [Member] Represents information pertaining to Novartis Pharma AG. Licensing and Commercialization Agreement Licensing And Commercialization Agreement [Member] Represents information pertaining to the license and commercialization agreement entered into by the entity. Research and Development Arrangement, Contract to Perform for Others [Line Items] Research and Development Arrangement, Contract to Perform for Others [Line Items] License fees paid Payments for License Fees Payments for License Fees 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 Sales Revenue, Services, Net Licensing and Commercialization Agreements Collaborative Arrangement Disclosure [Text Block] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] AOCI Attributable to Parent AOCI Attributable to Parent [Member] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] AOCI Attributable to Parent, Net of Tax [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Balance at beginning of period Current period changes in fair value before reclassifications, net of tax Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from accumulated other comprehensive income (loss), net of tax Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Total other comprehensive income (loss) Balance at end of period 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] Schedule of changes in accumulated other comprehensive income (loss) associated with the unrealized loss on available for sale securities Schedule of Accumulated Other Comprehensive Income (Loss) [Table 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 (in tranche) 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. Number of separate purchases provided for in financing agreement Financing Agreement, Number of Purchases Financing Agreement, Number of Purchases Proceeds from royalty purchase agreement Proceeds from Other Debt Previously recorded Alternative Minimum Tax Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit) Tax Cuts and Jobs Act, Change in Tax Rate, Income Tax Expense (Benefit) Decrease in deferred tax asset as a result of the Tax Cuts and Jobs Act of 2017 Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Change In Tax Rate, Deferred Tax Asset, Provisional Income Tax Expense Income tax provision (benefit) Income Tax Expense (Benefit) Cash and cash equivalents Cash Cash Investments in money market funds, U.S. Treasury securities and certain short-term investment-grade corporate debt securities with original maturities of 90 days or less Cash Equivalents, at Carrying Value Available for sale securities with maturities of greater than 90 days Net Loss Per Common Share Earnings Per Share [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 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 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) 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. 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 Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Schedule of collaboration revenue components Schedule of Collaborative Arrangements and Non-collaborative Arrangement Transactions [Table Text Block] Business Nature of Operations [Text Block] Income Statement [Abstract] Collaboration revenue Revenues Operating expenses: Operating Expenses [Abstract] Research and development Research and Development Expense General and administrative General and Administrative Expense Total operating expenses Operating Expenses Loss from operations Operating Income (Loss) Interest income Interest Income (Expense), Nonoperating, Net Other expense Other Nonoperating Income (Expense) Loss before income tax provision (benefit) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Net loss Net loss per common share: Basic and diluted (in dollars per share) Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic and diluted (in shares)