Net Loss Per Share - Number of Outstanding Stock Options, Warrants to Purchase Common Preferred Stock and Convertible Redeemable Preferred Stock Excluded from Computation of Diluted Net Income (Loss) Per Share (Details) - Excluded From Earnings Per Share Calculation - shares	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Stock options outstanding	11,497,626	7,287,369
Restricted stock units and restricted stock awards	2,841,861	578,657
Common equivalent shares from stock warrants	1,045,303	2,219,671
Antidilutive securities excluded from computation of earnings per share, amount, total	15,384,790	10,085,697