Net Income (Loss) Per Share - Effect of Antidilutive Securities (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	7,465	3,576
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,137	1,715
Unvested restricted stock awards
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	113	105
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,183	1,206
Shares of common stock issuable upon conversion of Series A-2 Preferred
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	110	0
Shares of common stock issuable upon conversion of Series B Preferred
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	1,339	0
Shares of common stock issuable upon conversion of Series C Preferred
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,583	0
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	0	550