Computation of 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, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 16,181	$ 1,270	$ 24,844	$ 10,822	$ (3,076)	$ 33,958	$ 42,295	$ 41,704
Interest expense on Convertible Senior Notes, net of tax (1)	180			791			1,669	4,152
Net income used for diluted earnings per share, if-converted method (1)	$ 16,361			$ 11,613			$ 43,964	$ 45,856
Basic weighted-average common shares outstanding (in shares)	41,642			39,290			40,520	37,490
Potentially dilutive shares issuable from Convertible Senior Notes, if-converted (in shares)	410			1,825			1,282	3,193
Potentially dilutive shares issuable from stock options and unvested RSUs (in shares)	1,154			1,774			1,249	1,784
Diluted weighted-average common shares outstanding, if-converted (in shares)	43,206			42,889			43,051	42,467
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)	223			0			198	161