Accounting Policies [Abstract] Accounting Policies [Abstract] Accounting Standards Update 2016-09 [Member] Accounting Standards Update 2016-09 [Member] Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accrued Expenses Accounts Payable, Current Accounts payable Accrued Liabilities, Current Accrued expenses Accrued expenses Accrued Professional Fees, Current Accrued professional fees Carrying value as of the balance sheet date of obligations incurred through that date and payable for expenses related to research and development. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Research And Development Expense Current Accrued research and development expenses Carrying value as of the balance sheet date of obligations incurred through that date and payable for expenses related to restructuring. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). Accrued Restructuring Costs Current Accrued restructuring Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less: Accumulated depreciation Accumulated Other Comprehensive Income (Loss), Net of Tax Accumulated other comprehensive loss AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Loss [Member] Additional Office Space [Member] Additional Office Space [Member] Additional Boston Office Space [Member] Additional Office Space two [Member] Additional Office Space Two [Member] San Diego Office Space [Member] Additional Paid in Capital, Common Stock Additional paid-in capital Additional Paid-in Capital [Member] Additional Paid-in Capital [Member] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net loss to net cash used in operating activities: Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Stock-based compensation expense Allocated Share-based Compensation Expense Total stock-based compensation expense Total stock-based compensation expense Amendment Flag Amendment Flag Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Total potentially dilutive shares Antidilutive Securities [Axis] Antidilutive Securities [Axis] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items] Antidilutive Securities, Name [Domain] Antidilutive Securities, Name [Domain] Assets Total assets Assets [Abstract] Assets Assets, Current Total current assets Assets, Current [Abstract] Current assets: Assets, Fair Value Disclosure Total cash equivalents and marketable securities AUSTRALIA Australia [Member] Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax Gross Unrealized Gains Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax Gross Unrealized Losses Available-for-sale Debt Securities, Amortized Cost Basis Amortized Cost Available-for-sale Securities, Debt Securities, Current Fair Value Marketable securities Available-for-sale Securities [Table Text Block] Summary of Marketable Securities Award Type [Axis] Award Type [Axis] Business Description and Basis of Presentation [Text Block] Nature of the Business and Basis of Presentation Capital Expenditures Incurred but Not yet Paid Property and equipment included in accounts payable Cash and Cash Equivalents, at Carrying Value Cash and cash equivalents at end of period Cash and cash equivalents at beginning of period Cash and cash equivalents Cash and Cash Equivalents [Axis] Cash and Cash Equivalents [Axis] Cash and Cash Equivalents, Fair Value Disclosure Cash equivalents Cash and Cash Equivalents, Period Increase (Decrease) Net increase (decrease) in cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Cash Equivalents Cash, Cash Equivalents, and Short-term Investments Total cash, cash equivalents and marketable securities Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Supplemental disclosure of non-cash investing and financing activities: Cash [Member] Cash [Member] Certificates of deposit due within one year. Certificates Of Deposit Due Within One Year [Member] Certificates of Deposit (Due within 1 Year) [Member] Certificates of Deposit [Member] Certificates of Deposit [Member] Chief Executive Officer [Member] CEO [Member] Commercial Paper [Member] Commercial Paper [Member] Commercial Paper, Not Included with Cash and Cash Equivalents Due Within One Year [Member] Commercial Paper, Not Included with Cash and Cash Equivalents Due Within One Year [Member] Commercial Paper (Due within 1 Year) [Member] Commitments and Contingencies Commitments and contingencies (Note 10) Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Text Block] Commitments and Contingencies Common Stock, Capital Shares Reserved for Future Issuance Shares of common stock reserved for issuance Common Stock [Member] Common Stock [Member] Common Stock, Par or Stated Value Per Share Common stock, par value Common stock, par value per share Common Stock, Shares Authorized Common stock, shares authorized Common Stock, Shares, Issued Common stock, shares issued Common Stock, Shares, Outstanding Common stock, shares outstanding Common Stock, Value, Issued Common stock, $0.001 par value per share; 115,000,000 shares authorized as of December 31, 2017 and 2016; 27,489,457 and 27,332,551 shares issued and outstanding as of December 31, 2017 and 2016, respectively Retirement Benefits [Abstract] Retirement Benefits [Abstract] Compensation Related Costs [Abstract] Compensation Related Costs [Abstract] Comprehensive Income (Loss), Net of Tax, Attributable to Parent Total comprehensive loss Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract] Comprehensive loss: Comprehensive Income, Policy [Policy Text Block] Comprehensive Loss Concentration Risk, Credit Risk, Policy [Policy Text Block] Concentration of Credit Risk and of Significant Suppliers Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Corporate Bond Securities [Member] Corporate Bonds [Member] Corporate Debt Securities Due After One Year Through Two Years [Member] Corporate Debt Securities Due After One Year Through Two Years [Member] Corporate Bonds (Due After 1 Year Through 2 Years) [Member] Corporate Debt Securities Due Within One Year [Member] Corporate Debt Securities Due Within One Year [Member] Corporate Bonds (Due within 1 Year) [Member] Counterparty Name [Axis] Counterparty Name [Axis] Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Credit Facility [Member] Credit Facility [Member] Credit Facility [Member] Current Fiscal Year End Date Current Fiscal Year End Date Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Text Block] Notes Payable Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Basis Spread on Variable Rate Debt facility interest rate Debt Instrument, Covenant Description Debt facility covenant description Debt Instrument, Description Debt facility description Debt Instrument, Description of Variable Rate Basis Debt facility interest rate description Debt Instrument, Face Amount Aggregate principal balance Maximum borrowings under term loan The fee, as a percentage of the term loan, due as a final payment. Debt Instrument Fee Percentage Debt facility fee percentage Debt Instrument, Increase, Accrued Interest Charges to interest expense of debt outstanding Debt Instrument, Interest Rate During Period Debt facility effective interest rate Debt Instrument, Interest Rate, Effective Percentage Debt facility effective interest rate Debt Instrument [Line Items] Debt Instrument [Line Items] Debt Instrument, Maturity Date Debt maturity date Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid Accretion related to final payment The aggregate amount of cash permitted to be maintained by the Australian subsidiary. Debt Instrument, Restrictive Covenants, Investment In Subsidiaries Aggregate value of cash maintained by Australian subsidiary, limit Debt Instruments [Abstract] Debt Instruments [Abstract] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument, Unamortized Discount Debt discount, net of accretion Deferred Charges, Policy [Policy Text Block] Deferred Offering Costs Deferred Tax Assets, Gross Gross deferred tax assets Total gross deferred tax assets Deferred Tax Assets, in Process Research and Development Capitalized research and development expenses Deferred Tax Assets, Net of Valuation Allowance Net deferred tax assets Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Total noncurrent deferred tax assets Deferred Tax Assets, Net of Valuation Allowance, Noncurrent Classification [Abstract] Noncurrent deferred tax assets: Deferred Tax Assets, Operating Loss Carryforwards Net operating loss carryforwards Deferred Tax Assets, Operating Loss Carryforwards, Domestic Operating loss carryforwards, federal Deferred Tax Assets, Operating Loss Carryforwards, State and Local Operating loss carry forwards, state Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences not separately disclosed. Deferred Tax Assets Other Noncurrent Other temporary differences Deferred Tax Assets, Tax Credit Carryforwards Tax credit carryforwards Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Stock-based compensation Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from accrued expenses. Deferred Tax Assets Tax Deferred Expense Reserves And Accruals Accrued Liabilities Noncurrent Accrued expenses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Legal Settlements Capitalized legal expenses Deferred Tax Assets, Valuation Allowance Valuation allowance as of end of year Valuation allowance as of beginning of year Valuation allowance Defined Contribution Plan, Cost Contribution expense Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay Percentage of employer's contribution on employee's base salary Denominator [Abstract] Denominator [Abstract] Denominator: The amount of cash paid for deposits on leased property. Deposits For Leased Property Deposits for leased property Depreciation Depreciation expense Development Based Milestones [Member] Development Based Milestones [Member] Development Based Milestones [Member] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Stock-Based Awards Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document And Entity Information [Abstract] Document Fiscal Period Focus Document Fiscal Period Focus Document Fiscal Year Focus Document Fiscal Year Focus Document Period End Date Document Period End Date Document Type Document Type Domestic Tax Authority [Member] Domestic Tax Authority [Member] Earning Per Share [Abstract] Earning Per Share [Abstract] Earning Per Share [Abstract] Earnings Per Share [Abstract] Earnings Per Share [Abstract] Earnings Per Share, Basic and Diluted Net loss per share, basic and diluted Earnings Per Share, Policy [Policy Text Block] Net Income (Loss) Per Share Earnings Per Share [Text Block] Net Loss Per Share Effective Income Tax Rate Reconciliation, Percent Effective income tax rate Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Federal statutory income tax rate Federal statutory income tax rate Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Percent Change in deferred tax asset valuation allowance Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Percent Impact of federal rate change related to tax reform Effective Income Tax Rate Reconciliation, Nondeductible Expense, Research and Development, Percent Nondeductible Australia research and development expenses Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Percent Stock compensation expense Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to orphan drug tax credit. Effective Income Tax Rate Reconciliation, Orphan Drug Tax Credits Orphan drug tax credit Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent Other items Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent State taxes, net of federal benefit Effective Income Tax Rate Reconciliation, Tax Credit, Research, Percent Federal and state research and development tax credit The percentage to be refunded pertaining to the tax incentive for qualified research and development activities. Effective Tax Incentive Rate Related To Research And Development Percentage of refundable tax incentive Employee-related Liabilities, Current Accrued payroll and related expenses Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Unrecognized stock-based compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Stock-based compensation recognized weighted average period Employee Stock Option [Member] Options to Purchase Common Stock [Member] Entity Central Index Key Entity Central Index Key Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Current Reporting Status Entity Current Reporting Status Entity Filer Category Entity Filer Category Entity Incorporation, Date of Incorporation Entity incorporation date Entity Public Float Entity Public Float Entity Registrant Name Entity Registrant Name Entity Voluntary Filers Entity Voluntary Filers Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Equipment [Member] Equipment [Member] Equity [Abstract] Equity [Abstract] Equity Component [Domain] Equity Component [Domain] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Assets Measured on Recurring and Nonrecurring Basis [Table Text Block] Summary of Cash Equivalents and Marketable Securities Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Fair Value Disclosures [Text Block] Fair Value Measurements and Marketable Securities Fair Value, Inputs, Level 1 [Member] Quoted Prices in Active Markets, (Level 1) [Member] Fair Value, Inputs, Level 2 [Member] Significant Other Observable Inputs (Level 2) [Member] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] First offering period end date. First Offering Period End Date End date of first offering period First offering period start date. First Offering Period Start Date Commencement date of first offering period Follow On Offering [Member] Follow On Offering [Member] Follow-on Offering [Member] Foreign Currency Transaction Gain (Loss), before Tax Foreign currency transaction gains (losses), net Foreign Currency Transaction Gain (Loss), Unrealized Unrealized foreign currency transaction gains (losses) Unrealized foreign currency transaction (gains) losses Furniture and Fixtures [Member] Furniture and Fixtures [Member] Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Loss on disposal of research and development equipment General and Administrative Expense General and administrative General and Administrative Expense [Member] General and Administrative [Member] Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill) Impairment losses on long-lived assets Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Impairment of Long-Lived Assets Income (Loss) from Continuing Operations before Income Taxes, Domestic Domestic Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Loss before income taxes Income (Loss) from Continuing Operations before Income Taxes, Foreign Foreign Income Statement [Abstract] Income Statement [Abstract] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Income Tax Disclosure [Text Block] Income Taxes Income Taxes Disclosure [Line Items] Income Taxes Disclosure [Line Items] Income Taxes Disclosure [Line Items] Income Taxes Disclosure [Table] Income Taxes Disclosure [Table] Income Taxes Disclosure [Table] Income Tax Expense (Benefit) Income tax benefit Income Tax, Policy [Policy Text Block] Income Taxes Increase (Decrease) in Accounts Payable Accounts payable Increase (Decrease) in Accrued Liabilities Accrued expenses Increase (Decrease) in Operating Capital [Abstract] Changes in operating assets and liabilities: Increase (Decrease) in Prepaid Expense and Other Assets Prepaid expenses and other current assets The increase (decrease) during the reporting period in tax incentive receivable, which represents the amount due from tax authorities. Increase Decrease In Tax Incentives Receivable Tax incentive receivable Intangible Assets, Finite-Lived, Policy [Policy Text Block] Patent Costs Interest Expense Interest expense Interest Paid Cash paid for interest Investment Company, Capital Share Transactions [Abstract] Investment Company, Capital Share Transactions [Abstract] Investment Income, Amortization of Premium Amortization of premium on marketable securities Investment Income, Net Interest income Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Axis] Lease Arrangement, Type [Domain] Lease Arrangement, Type [Domain] Lease Expiration Date Lease expiration date Leasehold Improvements [Member] Leasehold Improvements [Member] Lessee, Operating Lease, Renewal Term Lease extension period Liabilities Total liabilities Liabilities and Equity Total liabilities and stockholders' equity Liabilities and Equity [Abstract] Liabilities and Stockholders' Equity Liabilities, Current Total current liabilities Liabilities, Current [Abstract] Current liabilities: Liability for Uncertainty in Income Taxes, Current Uncertain tax position Maximum fee the Company is obligated to pay per licensed product. Licensing Fees Per Product Maximum Licensing fees per product maximum The minimum likelihood percentage threshold used to determine the amount of tax benefit to be recognized. Likelihood Percentage Minimum Percentage of likelihood to be realized upon ultimate settlement, description The minimum default amount over which the lender may exercise remedies against the Company. Line Of Credit Facility Debt Default Minimum Amount Credit facility default amount Line of Credit Facility, Periodic Payment, Interest Interest expense on credit facility Long-term Debt Total Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2018 Long-term Debt, Maturities, Repayments of Principal in Year Four 2021 Long-term Debt, Maturities, Repayments of Principal in Year Three 2020 Long-term Debt, Maturities, Repayments of Principal in Year Two 2019 Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Notes Payable, Noncurrent Notes payable, long-term Category of Item Purchased [Axis] Category of Item Purchased [Axis] Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-term Purchase Commitment, Category of Item Purchased [Domain] Marketable Securities, Policy [Policy Text Block] Marketable securities Marketable Securities, Unrealized Gain (Loss) Unrealized gain (loss) on marketable securities Market based stock options. Market Based Stock Options [Member] Market Based Stock Option [Member] Market-based vesting conditions. Market Based Vesting Conditions [Member] Market-Based Vesting Conditions [Member] Maximum [Member] Maximum [Member] Amount of payment due for milestones that have been achieved Milestone Liability Milestone payments due Amount of payment due upon reaching milestone. Milestone Payment Amount Milestone payments Minimum [Member] Minimum [Member] Money Market Funds [Member] Money Market Funds [Member] Net Cash Provided by (Used in) Financing Activities, Continuing Operations Net cash provided by (used in) financing activities Net Cash Provided by (Used in) Financing Activities, Continuing Operations [Abstract] Cash flows from financing activities: Net Cash Provided by (Used in) Investing Activities, Continuing Operations Net cash provided by (used in) investing activities Net Cash Provided by (Used in) Investing Activities, Continuing Operations [Abstract] Cash flows from investing activities: Net Cash Provided by (Used in) Operating Activities, Continuing Operations Net cash used in operating activities Net Cash Provided by (Used in) Operating Activities, Continuing Operations [Abstract] Cash flows from operating activities: Net Income (Loss) Attributable to Parent Net loss Net loss Net Income (Loss) Available to Common Stockholders, Basic Net loss The first year in which a net operating loss carryforward begins to expire. Net Operating Loss Carry Forward Expiration Year Begin Net operating loss carryforwards, beginning of expiration period Net proceeds from sale of securities. Net Proceeds From Sale Of Securities Net proceeds from sale of securities New Accounting Pronouncements, Policy [Policy Text Block] Recently Issued and Adopted Accounting Pronouncements Non Cash [Member] Non Cash [Member] Non-Cash [Member] Non Employee [Member] Nonemployee [Member] Non Employee [Member] Nonoperating Income (Expense) Total other income (expense), net Notes Payable Notes payable Notes Payable, Current Notes payable current portion Notes payable, current Numerator [Abstract] Numerator [Abstract] Numerator: Office Equipment [Member] Office Equipment [Member] Office Space Lease [Member] Office Space Lease [Member] Boston Office Space [Member] Operating Expenses Operating expenses Total operating expenses Operating Expenses [Abstract] Operating expenses: Operating Income (Loss) Loss from operations Operating Leases, Future Minimum Payments Due Total Operating Leases, Future Minimum Payments Due, Next Twelve Months 2018 Operating Leases, Future Minimum Payments, Due in Four Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2019 The number of options available to extend an operating lease. Operating Leases Number Of Options To Extend Lease Number of options to extend lease Operating Leases, Rent Expense, Net Operating lease, rental expense Operating Leases, Rent Expense, Sublease Rentals Sublease rental income Operating Loss Carryforwards Net operating loss carryforwards Option Indexed to Issuer's Equity, Type [Axis] Option Indexed to Issuer's Equity, Type [Axis] Option Indexed to Issuer's Equity, Type [Domain] Option Indexed to Issuer's Equity, Type [Domain] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Organization Consolidation And Presentation Of Financial Statements Disclosure [Table] Other Accrued Liabilities, Current Accrued other Other Assets, Noncurrent Other assets Other Commitments [Line Items] Other Commitments [Line Items] Other Commitments [Table] Other Commitments [Table] Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent Unrealized gain (loss) on marketable securities Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Total other comprehensive gain (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract] Other comprehensive gain (loss): Other Income and Expenses [Abstract] Other income (expense): Paid-in-Kind Interest Non-cash interest expense Payables and Accruals [Abstract] Payables and Accruals [Abstract] Payments for Restructuring Amounts paid during the period Payments of Stock Issuance Costs Payments of public offering costs Payments of public offering costs Payments to Acquire Available-for-sale Securities, Debt Purchases of marketable securities Payments to Acquire Property, Plant, and Equipment Purchases of property and equipment Pension and Other Postretirement Benefits Disclosure [Text Block] Retirement Plan The percentage of research and development costs to be reduced. Percentage Reduction Research And Development Costs Percentage of reduction in research and development costs Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Pre Commercialization Milestones [Member] Pre Commercialization Milestones [Member] Pre Commercialization Milestones [Member] Preferred Stock, Par or Stated Value Per Share Preferred stock, par value Preferred stock, par value per share Preferred Stock, Shares Authorized Preferred stock, shares authorized Preferred Stock, Shares Issued Preferred stock, shares issued Preferred Stock, Shares Outstanding Preferred stock, shares outstanding Preferred Stock, Value, Issued Preferred stock; $0.001 par value per share; 5,000,000 shares authorized as of December 31, 2017 and 2016; no shares issued and outstanding as of and December 31, 2017 and 2016 The cash outflow associated with the premium paid on marketable securities. Premium On Marketable Securities Premium on marketable securities Prepaid Expense and Other Assets, Current Prepaid expenses and other current assets Proceeds from Issuance of Common Stock Proceeds from offering, net of commissions and underwriting discounts Proceeds from public offerings, net of commissions and underwriting discounts Proceeds from Issuance of Shares under Incentive and Share-based Compensation Plans, Including Stock Options Proceeds from exercise of common stock options and employee stock purchase plan Proceeds from Notes Payable Proceeds from issuance of notes payable Proceeds from Sale and Maturity of Available-for-sale Securities Proceeds from sales and maturities of marketable securities Proceeds from Stock Options Exercised Proceeds from exercise of common stock options Product Commercialization Milestones [Member] Product Commercialization Milestones [Member] Product Commercialization Milestones [Member] Property, Plant and Equipment [Abstract] Property, Plant and Equipment [Abstract] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property Plant And Equipment Capitalized Interest Costs [Abstract] Property Plant And Equipment Capitalized Interest Costs [Abstract] Property Plant And Equipment Capitalized Interest Costs [Abstract] Property, Plant and Equipment Disclosure [Text Block] Property and Equipment, net Property, Plant and Equipment, Gross Property and equipment, gross Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Property, Plant and Equipment, Net Property and equipment, net Property and equipment, net Property, Plant and Equipment, Policy [Policy Text Block] Property and Equipment Property, Plant and Equipment [Table Text Block] Schedule of Property Plant and Equipment Net Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Useful Life Estimated useful life Property and equipment, Useful Life Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information Disclosure [Abstract] Quarterly Financial Information [Text Block] Quarterly Financial Data (Unaudited) Range [Axis] Range [Axis] Range [Domain] Range [Domain] Repayments of Notes Payable Repayments of notes payable Counterparty Name [Domain] Counterparty Name [Domain] Research and Development [Abstract] Research and Development [Abstract] Research and Development Expense Research and development Research and Development Expense [Member] Research and Development [Member] Research and Development Expense, Policy [Policy Text Block] Research and Development Costs Research and Development Expenses [Table] Research and Development Expenses [Table] Research and Development Expenses [Table] Research and Development Tax Incentive [Line Items] Research And Development Tax Incentive [Line Items] Research and Development Tax Incentive [Line Items] Disclosure of accounting policy for costs associated with research and development contracts. Research Contract Costs and Accruals [Policy Text Block] Research Contract Costs and Accruals Research, Development, and Computer Software Disclosure [Text Block] Australia Research and Development Tax Incentive Cash and Cash Equivalents [Domain] Cash and Cash Equivalents [Domain] Restricted Cash and Investments Loan agreement minimum liquidity required Restricted cash and investments as percentage of outstanding principal amount. Restricted Cash And Investments As Percentage Of Outstanding Principal Amount Percentage equivalent of cash, cash equivalents and marketable securities balance Restricted Stock Units (RSUs) [Member] Restricted Stock Units (RSUs) [Member] Restructuring and Related Activities [Abstract] Restructuring and Related Activities [Abstract] Restructuring and Related Activities Disclosure [Text Block] Restructuring Restructuring and Related Cost, Incurred Cost Restructuring expenses incurred during the period Restructuring and Related Cost, Number of Positions Eliminated, Period Percent Percentage of workforce reduction Restructuring Charges Restructuring charges Restructuring Costs Restructuring costs Restructuring Reserve Restructuring reserve ending balance Restructuring reserve beginning balance Restructuring Reserve [Abstract] Restructuring Reserve [Abstract] Restructuring Reserve Disclosures [Abstract] Restructuring Reserve Disclosures [Abstract] Retained Earnings (Accumulated Deficit) Accumulated deficit Retained Earnings [Member] Accumulated Deficit [Member] Revenues Revenue Sale of Stock [Domain] Sale of Stock [Domain] Scenario, Plan [Member] Scenario, Plan [Member] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Schedule of Accrued Liabilities [Table Text Block] Schedule of Accrued Expenses Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table] Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block] Summary of Common Stock Equivalents Outstanding Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Line Items] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Schedule of Net Deferred Tax Assets Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Computation of Basic and Diluted Earnings Per Share Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Reconciliation of Federal Statutory Income Tax Rate Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block] Summary of Stock-Based Compensation Expense Related to Stock Options and Restricted Common Stock Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of Future Minimum Lease Payments for Operating Leases Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block] Schedule of Domestic and Foreign Components of Loss Before Income Taxes Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of Estimated Future Principal Payments Tabular disclosure of notes payable. Includes, but is not limited to, current and long-term portions. Schedule of Notes Payable [Table Text Block] Schedule of Notes Payable Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Quarterly Financial Information [Table Text Block] Schedule of Unaudited Consolidated Financial Statements Schedule of Restructuring and Related Costs [Table] Schedule of Restructuring and Related Costs [Table] Restructuring and Related Costs [Table Text Block] Summary of Restructuring Costs by Category Schedule of Restructuring Reserve by Type of Cost [Table Text Block] Summary of Restructuring Reserve Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of Stock Option Activity Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Assumptions used to Determine Fair Value of Stock Options Granted Second offering period end date. Second Offering Period End Date End date of second offering period Second offering period start date. Second Offering Period Start Date Commencement date of second offering period Secured Debt [Member] Secured Debt [Member] Geographical [Domain] Geographical [Domain] Segment Reporting, Policy [Policy Text Block] Segment Data Share-based Compensation Stock-based compensation expense The total grant-date fair value of Price Target Options. Share Based Compensation Arrangement By Share Based Payment Award Aggregate Grant Date Fair Value Total fair value of Price Target Options Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Term of stock option Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Stock option vesting percentage Share-based Compensation Arrangement by Share-based Payment Award, Description Stock option vesting description Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date Discount from market price of the company's common stock offering Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested Aggregate intrinsic value of restricted stock units vested during the period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Number of restricted stock units granted Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Number of restricted stock units unvested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Weighted average grant-date fair value of restricted stock units granted Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Expected term (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected volatility Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Common stock available for issuance Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Aggregate intrinsic value, options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Shares issuable under options, options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted-average exercise price, options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Average remaining contractual life, options exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Aggregate intrinsic value of stock options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Shares issuable under options, forfeited Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Shares issuable under options, granted Stock based compensation, stock options granted Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Weighted average grant-date fair value of stock options granted The number of shares, as a percentage, that will vest upon achievement of the target. 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