Net Income Per Share - Schedule of Shares Excluded From Computation of Diluted Net Income (Loss) Per Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net income (loss) per share (in shares)	4,545	16,505	11,796
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net income (loss) per share (in shares)	625	1,251	1,251
Outstanding stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net income (loss) per share (in shares)	3,271	13,803	8,981
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of net income (loss) per share (in shares)	649	1,451	1,564