Net Loss Per Share of Common Stock - Antidilutive Securities (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding	10,207,254	9,417,099	8,026,671
Warrants to purchase common stock
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding	31,130	39,824	39,824
Stock option awards
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding	6,425,832	7,006,472	6,825,142
Restricted stock unit awards
Securities excluded from the calculation of weighted average common shares outstanding
Total anti-dilutive securities outstanding	3,750,292	2,370,803	1,161,705