| Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] | 
        
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   |        |    2013   |        |    2012   |        |     |       |        |        |        |        |        |        |        |     |   Tax provision (benefit)   |        |        |        |        |        |        |        |     |   Current   |        |        |        |        |        |        |        |     |   Federal   |        |    $   |       |        |    $   |       |        |     |   State   |        |        |       |        |        |       |        |     |   Total current   |        |        |       |        |        |       |        |     |       |        |        |        |        |        |        |        |     |   Deferred   |        |        |        |        |        |        |        |     |   Federal   |        |        |    (4,705,250)   |        |        |    (3,225,486)   |        |     |   State   |        |        |    134,225   |        |        |    2,291,913   |        |     |   Total deferred   |        |        |    (4,571,025)   |        |        |    (933,573)   |        |     |       |        |        |        |        |        |        |        |     |   Change in valuation allowance   |        |        |    4,571,025   |        |        |    933,573   |        |     |   Total   |        |    $   |       |        |    $   |       |        |          
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        | Schedule of Deferred Tax Assets and Liabilities [Table Text Block] | 
        
   Deferred tax assets consisted of the following at December 31:     
     |       |        |    2013   |        |    2012   |        |     |       |        |        |        |        |        |        |        |     |   Deferred tax assets   |        |        |        |        |        |        |        |     |   Federal net operating loss   |        |    $   |    25,731,718   |        |    $   |    22,343,084   |        |     |   Federal research and development tax credit carryforwards   |        |        |    2,480,417   |        |        |    1,969,426   |        |     |   State net operating loss   |        |        |    2,070,642   |        |        |    2,252,566   |        |     |   State research and development tax credit carryforwards   |        |        |    724,200   |        |        |    633,571   |        |     |   Capitalized research and development expenses   |        |        |    11,128,803   |        |        |    11,068,868   |        |     |   Stock-based compensation expense   |        |        |    1,599,005   |        |        |    842,174   |        |     |   Intangible assets   |        |        |    380,339   |        |        |    440,556   |        |     |   Charitable contribution carryforwards   |        |        |    34,850   |        |        |    43,350   |        |     |   Accrued liabilities   |        |        |    26,112   |        |        |    25,199   |        |     |   Total deferred tax assets   |        |        |    44,176,086   |        |        |    39,618,794   |        |     |       |        |        |        |        |        |        |        |     |   Deferred tax liabilities   |        |        |        |        |        |        |        |     |   Depreciable assets   |        |        |    (257,314)   |        |        |    (271,049)   |        |     |   Total deferred tax liabilities   |        |        |    (257,314)   |        |        |    (271,049)   |        |     |       |        |        |        |        |        |        |        |     |   Net deferred tax assets   |        |        |    43,918,772   |        |        |    39,347,745   |        |     |   Less valuation allowance   |        |        |    (43,918,772)   |        |        |    (39,347,745)   |        |     |   Total deferred tax assets   |        |    $   |       |        |    $   |       |        |         
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