Accounting Policies [Abstract] Accounting Policies [Abstract] Accounts Payable Accrued Liabilities And Other Liabilities Disclosure Current [Text Block] Accrued Expenses Accounts Payable Current Accounts payable Accounts Receivable Net Current Accounts receivable Accretion Expense Accretion of final interest payment on term loans Accrued clinical expense, current. Accrued Clinical Expense Current Clinical trial related Accrued drug supply and development current. Accrued Drug Supply And Development Current Drug supply and development Accrued Liabilities Current Accrued expenses Total Accrued Professional Fees Current Professional fees Additional Paid In Capital Additional paid-in capital Adjustment Of Warrants Granted For Services Fair value adjustment of warrants Adjustments 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 Allocated Share Based Compensation Expense Stock-based compensation expense Amendment Flag Amendment Flag Amortization Of Financing Costs And Discounts Amortization of deferred financing costs and debt discount Amount payable to lessor in respect of default on rental obligation. Amount Payable To Lessors In Respect Of Default On Rental Obligation Amount payable to lessors in respect of default on rental obligation Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount Antidilutive securities excluded from computation of earnings per share, amount Antidilutive Securities Excluded From Computation Of Earnings Per Share By 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] Arrangements And Nonarrangement Transactions [Member] Arrangements and Non-arrangement Transactions [Domain] Assets Total assets Assets [Abstract] Assets Assets Current Total current assets Assets Current [Abstract] Current assets: Awarded contract for research and development. Awarded Contract For Research And Development Awarded contract for development, amount Award Type [Axis] Award Type [Axis] Basis Of Accounting Policy Policy [Text Block] Basis of Presentation Biomedical advanced research and development authority. Biomedical Advanced Research And Development Authority [Member] Biomedical Advanced Research and Development Authority (BARDA) [Member] 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 and cash equivalents, fair value Cash and cash equivalents maturity period description. Cash And Cash Equivalents Maturity Period Description Maturity period of highly liquid investments Cash And Cash Equivalents Period Increase Decrease Net (decrease) increase in cash and cash equivalents Cash And Cash Equivalents Policy [Text Block] Cash and Cash Equivalents Cash And Cash Equivalents Restricted Cash And Cash Equivalents Policy Restricted Cash Cash [Member] Cash [Member] Class Of Stock [Domain] Class of Stock [Domain] Class Of Warrant Or Right [Axis] Class of Warrant or Right [Axis] Class Of Warrant Or Right Cancelled Class Of Warrant Or Right Cancelled Number of shares cancelled Class Of Warrant Or Right [Domain] Class of Warrant or Right [Domain] Class Of Warrant Or Right Exercise Price Of Warrants Or Rights Warrants to purchase shares of stock, shares, exercise price per share Class Of Warrant Or Right Issued Date One [Member] Class Of Warrant Or Right Issued Date One [Member] May 2011 (Term Loan) [Member] Class Of Warrant Or Right Issued Date Two [Member] Class Of Warrant Or Right Issued Date Two [Member] December 2012 (2012 Term A Loan) [Member] Class Of Warrant Or Right Number Of Securities Called By Warrants Or Rights Warrants to purchase shares of stock, shares Class of warrant or right term exercise period. Class Of Warrant Or Right Term Exercise Period Warrants to purchase shares of stock, term Collateralized Credit Card Securities [Member] Credit Card [Member] Commitments And Contingencies Commitments and contingencies Common Stock Capital Shares Reserved For Future Issuance Number of common stock to be issued Common Stock Par Or Stated Value Per Share Common stock, par value Common Stock Shares Authorized Common stock, shares authorized Common Stock Shares Issued Common stock, shares issued Number of shares issued Common Stock Shares Outstanding Common stock, shares outstanding Common Stock Value Common stock, par value $0.001 per share; 125,000 shares authorized; 25,909 and 25,629 shares issued and outstanding at June 30, 2014 and December 31, 2013, respectively Comprehensive Income Net Of Tax Comprehensive loss Comprehensive Income Policy Policy [Text Block] Comprehensive Loss Concentration Risk Credit Risk Concentrations of Credit Risk and Off-Balance Sheet Risk Consolidation Policy [Text Block] Principles of Consolidation Contract Maturity Date Contract Maturity Date Contract maturity date Contract term. Contract Term Awarded contract for development, contract period Conversion Of Stock Amount Converted 1 Conversion of convertible preferred stock into common stock Counterparty Name [Axis] Counterparty Name [Axis] Current Fiscal Year End Date Current Fiscal Year End Date Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt instrument additional borrowing capacity amount. Debt Instrument Additional Borrowing Capacity Amount Debt, additional borrowing capacity Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument Carrying Amount Total term loan payments Debt instrument interest only period. Debt Instrument Interest Only Period Interest payment period Debt Instrument Interest Rate Stated Percentage Debt, stated interest rate Debt Instrument [Line Items] Debt Instrument [Line Items] Debt Instrument Maturity Date Debt, maturity date Debt instrument maximum borrowing capacity. Debt Instrument Maximum Borrowing Capacity Debt, borrowing capacity Debt Instrument Name [Domain] Debt Instrument, Name [Domain] Debt instrument number of installment. Debt Instrument Number Of Installment Debt, number of installments Debt instrument redemption rate. Debt Instrument Redemption Rate Debt, stated interest rate at maturity date Debt Instrument [Table] Schedule of Long-term Debt Instruments [Table] Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Text Block] Schedule of Prepaid Expenses and Other Current Assets Deferred Revenue Current Deferred revenue Depreciation And Amortization Depreciation and amortization Development Stage Enterprise Deficit Accumulated During Development Stage Losses incurred since inception Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Stock-based Compensation Document and entity information. 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 Earnings Per Share Basic And Diluted Net loss per share-basic and diluted Earnings Per Share Policy [Text Block] Net Loss per Common Share Employee Related Liabilities Current Salaries and benefits Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items] Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition 1 Weighted-average period of unrecognized stock-based compensation expense related to unvested stock options Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options Unrecognized stock-based compensation expense related to unvested stock options Employee Stock Option [Member] Outstanding Stock Options [Member] Entity Central Index Key Entity Central Index Key Entity Common Stock Shares Outstanding Entity Common Stock, Shares Outstanding Entity Filer Category Entity Filer Category Entity Incorporation Date Of Incorporation Company incorporation date Entity Registrant Name Entity Registrant Name Estimated forfeiture rate. Estimated Forfeiture Rate Estimated forfeiture rate Fair Value Adjustment Of Warrants Decrease in fair value recognized in net loss 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 Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Table [Text Block] Financial Instruments Measured at Fair Value Fair Value By Fair Value Hierarchy Level [Axis] Fair Value, Hierarchy [Axis] Fair Value Inputs Level 1 [Member] Level 1 [Member] Fair Value Measurement Policy Policy [Text Block] Fair Value Measurements Fair Value Measurements Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] First tranche. First Tranche [Member] First Tranche [Member] Gain Loss On Disposition Of Assets Loss from disposal of property and equipment General And Administrative Expense General and administrative General And Administrative Expense [Member] General and Administrative [Member] Government Contract Receivable Awarded contract for development, amount to be funded Government Contract Receivable Unbilled Amounts Unbilled accounts receivable Income Statement [Abstract] Income Statement [Abstract] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Income Tax Policy [Text Block] Income Taxes Increase Decrease In Accounts Payable Accounts payable Increase Decrease In Accounts Receivable Accounts receivable Increase Decrease In Accrued Liabilities Accrued expenses Increase Decrease In Deferred Revenue Deferred revenue Increase Decrease In Operating Capital [Abstract] Changes in operating assets and liabilities: Increase Decrease In Prepaid Deferred Expense And Other Assets Prepaid expenses and other current assets Initial Public Offerings Completion Date Initial Public Offerings Completion Date Initial public offering completion date Interest Expense Interest expense Interest Paid Cash paid for interest Investment Income Interest Interest income January First Two Thousand Twelve To April Thirtieth Two Thousand Fifteen [Member] January First Two Thousand Twelve To April Thirtieth Two Thousand Fifteen [Member] January 1, 2012 through April 30, 2015 [Member] Letter Of Credit [Member] Letter of Credit [Member] Liabilities And Stockholders Equity Total liabilities, convertible preferred stock and stockholders' equity Liabilities And Stockholders Equity [Abstract] Liabilities and stockholders' equity Liabilities Current Total current liabilities Liabilities Current [Abstract] Current liabilities: Licensing Agreements [Member] License Agreement with Harvard University (the University) [Member] Loan agreement number of tranches. Loan Agreement Number Of Tranches Debt, number of tranches Loans Payable Current Current portion of term loan payable Current term loan payable (net) Loans Payable Fair Value Disclosure Fair value of loans payable Long Term Debt Current Including Debt Discount And Issuance Costs Long Term Debt Current Including Debt Discount And Issuance Costs Current term loan payable Long Term Debt Maturities Repayments Of Principal In Year Three 2016 Long Term Debt Maturities Repayments Of Principal In Year Two 2015 Long Term Debt Maturities Repayments Of Principal Remainder Of Fiscal Year 2014 (6 months remaining) Long Term Debt Non Current Including Debt Discount And Issuance Costs Long Term Debt Non Current Including Debt Discount And Issuance Costs Term loan payable, less current portion Long Term Debt [Text Block] Long-Term Debt Longterm Debt Type [Axis] Long-term Debt, Type [Axis] Longterm Debt Type [Domain] Long-term Debt, Type [Domain] Long Term Loans Payable Term loan Term loan payable, net Maximum [Member] Maximum [Member] Milestone payments. Milestone Payments Milestone payments Minimum [Member] Minimum [Member] Money Market Funds [Member] Money Market Funds, Included in Cash Equivalents [Member] National institutes of health, national institute of allergy and infectious diseases. National Institutes Of Health National Institute Of Allergy And Infectious Diseases [Member] National Institutes of Health's (NIH) National Institute of Allergy and Infectious Diseases (NIAID) Division [Member] Net Cash Provided By Used In Financing Activities [Abstract] Financing activities Net Cash Provided By Used In Financing Activities Continuing Operations Net cash (used in) provided by financing activities Net Cash Provided By Used In Investing Activities [Abstract] Investing activities Net Cash Provided By Used In Investing Activities Continuing Operations Net cash used in investing activities Net Cash Provided By Used In Operating Activities [Abstract] Operating activities Net Cash Provided By Used In Operating Activities Continuing Operations Net cash used in operating activities Net Income Loss Net loss Net loss New Accounting Pronouncements Policy Policy [Text Block] Recent Accounting Pronouncements Issued and Adopted Nonoperating Income Expense Other expense, net Nonoperating Income Expense [Abstract] Other income (expense) Number Of Operating Segments Number of operating segment Operating Costs And Expenses Total operating expenses Operating Costs And Expenses [Abstract] Operating expenses Operating Income Loss Loss from operations Organization Consolidation And Presentation Of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Organization and Operations Other Accrued Liabilities Current Other Other Assets Current Other Other Assets Noncurrent Other assets Other Liabilities Noncurrent Accrued final interest payment on term loan Other Nonoperating Income Expense Other income Other Prepaid Expense Current Prepaid dues Parties To Contractual Arrangement [Axis] Parties to Contractual Arrangement [Axis] Parties To Contractual Arrangement [Member] Parties to Contractual Arrangement [Domain] Payables And Accruals [Abstract] Payables and Accruals [Abstract] Payments For Royalties Payment for additional intellectual property Payments To Acquire Property Plant And Equipment Purchases of property and equipment Percentage threshold of outstanding stock for determining availability of grants. Percentage Threshold Of Outstanding Stock For Determining Availability Of Grants Percentage threshold of shares outstanding for determining availability of grants Phase three clinical trial. Phase Three Clinical Trial [Member] Phase Three Clinical Trial [Member] Potential future payments for regulatory milestones. Potential Future Payments For Regulatory Milestones Upfront and milestone payments Preferred Stock Par Or Stated Value Per Share Preferred stock, par value 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 Preferred stock, par value $0.001 per share; 5,000 shares authorized; no shares issued and outstanding Prepaid clinical expenses. Prepaid Clinical Expenses Prepaid clinical costs Prepaid Expense And Other Assets Current Prepaid expenses and other current assets Total Prepaid Expense And Other Current Assets Disclosure [Text Block] Prepaid Expense And Other Current Assets Disclosure [Text Block] Prepaid Expenses and Other Current Assets Prepaid Insurance Prepaid insurance Prepaid Manufacturing Fees Current Prepaid Manufacturing Fees Current Prepaid manufacturing costs Prepaid Rent Prepaid rent Proceeds From Grantors Awarded contract for development, amount received Proceed from awarded contract for development Proceeds From Issuance Of Long Term Debt Debt, borrowing Proceeds from issuance of term loan payable Proceeds From Issuance Or Sale Of Equity Proceeds from sale of common stock, net of issuance costs Proceeds From Stock Options Exercised Proceeds from exercise of stock options