Income Taxes - Deferred Tax Assets and Liabilities (Detail) (USD $)
Dec. 31, 2013
Dec. 31, 2012
Deferred tax assets:    
Net operating loss carryforwards $ 22,346,862 $ 8,329,939
Accrued expenses    215,865
Accrued employee benefits 377,049 282,268
Capitalized research and development costs 31,891 27,516
Research and development credit 1,874,939 1,928,714
Nonqualified stock options 53,686   
Deferred revenue    643,669
Deferred tax liabilities:    
Depreciation 102,916 130,017
Net deferred tax asset 24,787,343 11,557,988
Valuation allowance (24,787,343) (11,557,988)
Net deferred tax asset