Leases [Abstract] 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] Accounting Standards Update 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] Right-of-use asset, net Operating Lease, Right-of-Use Asset Operating lease liability Operating Lease, Liability Estimated incremental borrowing rate Operating Lease, Weighted Average Discount Rate, Percent Lease and rent expense Operating Lease, Expense Operating lease, payments Operating Lease, Payments Weighted average remaining lease term Operating Lease, Weighted Average Remaining Lease Term Share-based Payment Arrangement [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] 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. Award Type [Axis] Award Type [Axis] Award Type [Domain] Award Type [Domain] Stock options Share-based Payment Arrangement, Option [Member] Restricted stock units Restricted Stock [Member] ESPP Employee Stock [Member] Stock Option and Compensation Plans Share-based Compensation Arrangement by Share-based Payment Award [Line Items] 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 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. 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 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 Unrecognized compensation costs, net of estimated forfeitures Share-based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount Number of shares available for future purchase (in shares) Share-Based Compensation Arrangement By Share-based Payment Award, Number Of Shares Available For Future Purchase Share-Based Compensation Arrangement By Share-based Payment Award, Number Of Shares Available For Future Purchase 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 Cash, Cash Equivalents, and Short-term Investments [Abstract] Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value 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 Debt Securities, Available-for-sale Accounting Policies [Abstract] Number of operating segments Number of Operating Segments Number of reporting segments Number of Reportable Segments Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Statistical Measurement [Axis] Statistical Measurement [Axis] Statistical Measurement [Domain] Statistical Measurement [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Property and equipment Property, Plant and Equipment [Line Items] Estimated useful lives Property, Plant and Equipment, Useful Life Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Share-Based Compensation Share-based Payment Arrangement [Text Block] 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 Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Statement of Financial Position [Abstract] Assets Assets [Abstract] Current assets Assets, Current [Abstract] Cash and cash equivalents 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 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 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, 41,601,639 and 41,397,197 shares issued and outstanding at September 30, 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 Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Earnings Per Share [Abstract] Basic and diluted net loss per common share calculation: Earnings Per Share, Basic and Diluted [Abstract] Net loss Net Income (Loss) Attributable to Parent 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 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 in Period Expired (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Outstanding at end of year (in shares) Vested and exercisable, September 30, 2019 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number Vested and expected to vest, September 30. 2019 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] 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 Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Expired (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Outstanding at end of year (in dollars per share) Vested and exercisable, September 30, 2019 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price Vested and expected to vest, September 30. 2019 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price 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] Operating Leases Lessee, Operating Leases [Text Block] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] 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] 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 Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Smaller Reporting Company Entity Small Business Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company 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 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] Number of shares reserved for issuance under the Plan (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized 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] 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 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 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 and other expense Depreciation Gain on sale of property and equipment Gain (Loss) on Disposition of Property Plant Equipment Deferred income taxes Deferred Income Taxes and Tax Credits Share-based compensation Share-based Payment Arrangement, Noncash Expense Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Income tax receivable Increase (Decrease) in Income Taxes Receivable Prepaid expense and other assets Increase (Decrease) in Prepaid Expense and Other 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 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] Proceeds from sale of assets Proceeds from Sale of Productive Assets Net cash provided by (used in) 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 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 tax refunds received Income Taxes Paid, Net Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Income tax benefit Income Tax Expense (Benefit) Organization, Consolidation and Presentation of Financial Statements [Abstract] Business Nature of Operations [Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Stock Preferred Stock [Member] Common Stock Common Stock [Member] Additional paid-in capital Additional Paid-in Capital [Member] Accumulated Deficit Retained Earnings [Member] Statement 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 under employee stock compensation plans (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 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 Issuance of common stock (in shares) Stock Issued During Period, Shares, New Issues Balance at end of period (in shares) 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] Subsequent Events [Abstract] Subsequent Event [Table] Subsequent Event [Table] Scenario [Axis] Scenario [Axis] Scenario [Domain] Scenario [Domain] Forecast Forecast [Member] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] License 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. 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. Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] Subsequent Event [Line Items] Subsequent Event [Line Items] Payment made on achievement of milestone Payment Made On Achievement Of Milestone Payment Made On Achievement Of Milestone 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] Cash, Cash Equivalents and Available for Sale Securities Cash, Cash Equivalents, and Short-term Investments [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, December 31, 2018 (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, September 30, 2019 (in shares) Expected to vest (in shares) Share-Based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Expected To Vest, Number Share-Based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Expected To Vest, Number 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, December 31, 2018 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value 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, September 30, 2019 (in dollars per share) 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. Schedule of Commitments and Contingencies [Table] Schedule of Commitments and Contingencies [Table] Schedule of information pertaining to commitments and contingencies. Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Research and development Research and Development Expense [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] 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] University of Florida Research Foundation (UFRF) University of Florida Research Foundation (UFRF) [Member] University of Florida Research Foundation (UFRF) [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] 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] GA Product GA Product [Member] GA Product [Member] Wet AMD Product Wet AMD Product [Member] Wet AMD Product [Member] 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. Payments for license fees Payments For License Fees Payments for License Fees Number of licensed products Number Of Licensed Products Number of Licensed Products Shares issued for license fees Shares Issued For License Fees Shares Issued For License Fees Contingent consideration arrangements, maximum amount 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 Contingent consideration arrangements, maximum amount (in shares) Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Shares Issuable, High Asset Acquisition, Contingent Consideration Arrangements, Range Of Outcomes, Shares Issuable, High 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 Asset Acquisition, Contingent Consideration Arrangements, Contingently Issuable Shares As A Percentage Of Shares Outstanding Fees and costs paid to plaintiff's counsel Litigation Settlement, Amount Awarded to Other Party Schedule of Allocation of Share-based Compensation Costs by Award Type Share-based Payment Arrangement, Cost by Plan [Table Text Block] Schedule of Allocation of Share-based Compensation Costs by Financial Statement Line Schedule Of Compensation Cost For Share-based Payment Arrangements, Allocation Of Share-based Compensation Costs By Financial Statement Line [Table Text Block] Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Financial Statement Line [Table Text Block] 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 Company's outstanding shares of RSU awards Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Income Statement and Statement of Comprehensive Income [Abstract] [Abstract] Income Statement and Statement of Comprehensive Income [Abstract] [Abstract] 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 income (expense) Other Nonoperating Income (Expense) Loss before income tax provision (benefit) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax provision (benefit) Net loss Comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent Net loss per common share: Weighted average common shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Fair Value Measurements Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring [Text Block] Compensation Related Costs [Abstract] General and administrative General and Administrative Expense [Member] Share-based compensation expense Share-based Payment Arrangement, Expense Subsequent Event Subsequent Events [Text Block] 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 Net Loss Per Common Share Earnings Per Share [Text Block] Summary of Operating Lease Liability, Maturity Lessee, Operating Lease, Liability, Maturity [Table Text Block] Remainder of 2019 Lessee, Operating Lease, Liability, Payments, Remainder of Fiscal Year 2020 Lessee, Operating Lease, Liability, Payments, Due Year Two Total remaining obligation Lessee, Operating Lease, Liability, Payments, Due Less imputed interest Lessee, Operating Lease, Liability, Undiscounted Excess Amount Present value of lease liabilities Restricted stock units Restricted Stock Units (RSUs) [Member] Employee stock purchase plan