Net Loss Per Share - Weighted-Average Anti-Dilutive Securities Not Included in Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in diluted net loss per share (in shares)	18,310	1,638
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in diluted net loss per share (in shares)	1,164	629
Unvested restricted share awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in diluted net loss per share (in shares)	84	47
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in diluted net loss per share (in shares)	9,440	962
Series A convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities not included in diluted net loss per share (in shares)	7,622