Earnings Per Share - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator:
Net income (loss)	$ (738)	$ 7,116	$ 4,374	$ 5,678	$ 4,765	$ 4,225	$ (1,905)	$ (3,136)	$ 10,052	$ (5,043)	$ 17,168	$ (817)	$ 16,430	$ 3,949	$ (32,389)
Denominator:
Denominator for basic earnings per share—weighted-average shares outstanding (in shares)													53,851	53,607	52,791
Effect of dilutive securities:
Employee stock options and restricted common shares (in shares)													1,093	728	0
Contingently issuable shares (in shares)													0	125	0
Denominator for dilutive earnings per share (in shares)													54,944	54,460	52,791
Basic earnings (loss) per share (in USD per share)	$ (0.01)	$ 0.13	$ 0.08	$ 0.11	$ 0.09	$ 0.08	$ (0.04)	$ (0.06)	$ 0.19	$ (0.09)	$ 0.32	$ (0.02)	$ 0.31	$ 0.07	$ (0.61)
Diluted earnings (loss) per share (in USD per share)	$ (0.01)	$ 0.13	$ 0.08	$ 0.10	$ 0.09	$ 0.08	$ (0.04)	$ (0.06)	$ 0.18	$ (0.09)	$ 0.31	$ (0.02)	$ 0.30	$ 0.07	$ (0.61)