Computation of (Loss) Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income (loss)	$ 10,822	$ (5,525)	$ 41,704	$ (3,077)
Interest expense on Convertible Senior Notes, net of tax	791	0	4,152	0
Net income (loss) used for diluted earnings per share, if-converted method	$ 11,613	$ (5,525)	$ 45,856	$ (3,077)
Basic weighted-average common shares outstanding (in shares)	39,290	33,913	37,490	33,538
Potentially dilutive shares issuable from Convertible Senior Notes, if-converted (in shares)	1,825	0	3,193	0
Potentially dilutive shares issuable from stock options and unvested RSUs (in shares)	1,774	0	1,784	0
Diluted weighted-average common shares outstanding, if-converted (in shares)	42,889	33,913	42,467	33,538
Stock options
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive shares excluded from calculation due to anti-dilutive effect (in shares)	0	0	161	1,121