Earnings Per Share - Schedule of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount				1,200
Numerator:
Net (loss) income	$ (44,937)	$ 7,116	$ (46,921)	$ 17,168
Denominator:
Weighted-average shares outstanding – basic (in shares)	51,688	53,964	52,384	53,962
Effect of dilutive securities:
Employee and director stock options and restricted common shares (in shares)	0	1,225	0	1,165
Weighted-average shares outstanding – diluted (in shares)	51,688	55,189	52,384	55,127
Basic earnings per share (in dollars per share)	$ (0.87)	$ 0.13	$ (0.90)	$ 0.32
Diluted earnings per share (in dollars per share)	$ (0.87)	$ 0.13	$ (0.90)	$ 0.31