Consolidated Statements of Comprehensive Loss (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Net loss $ (53,305,938) $ (23,921,563) $ (10,471,330)
Other comprehensive loss:      
Foreign currency translation (loss) gain (10,382) (8,264) (180,049)
Unrealized (loss) on short-term investments (11,928)    
Total comprehensive loss $ (53,328,248) $ (23,929,827) $ (10,651,379)