Summary of Significant Accounting Policies - Basic and Diluted Net Loss per Share Computations (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accounting Policies [Abstract]
Net loss	$ (7,620,256)	$ (6,416,447)
Weighted average shares outstanding used to compute basic and diluted net income or loss per share	55,343,877	38,263,434
Basic and diluted net loss per share	$ (0.14)	$ (0.17)