Computation of Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Dilutive Securities Included And Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Net income	$ 67,652	$ 40,237	$ 1,270	$ 24,844	$ 107,889	$ 26,114
Interest expense on Convertible Senior Notes, net of tax (1)	179		0		360	1,489
Net income used for diluted earnings per share, if-converted method (1)	$ 67,831		$ 1,270		$ 108,249	$ 27,603
Basic weighted-average common shares outstanding	42,117		40,209		42,086	39,957
Dilutive potential shares issuable from Convertible Senior Notes (1)	392		6		401	1,062
Dilutive potential shares issuable from stock options and unvested RSUs	1,237		1,214		1,087	1,296
Diluted weighted-average common shares outstanding, if-converted (1)	43,746		41,429		43,574	42,315
Potentially dilutive shares excluded from calculation due to anti-dilutive effect (2)					1	183
Weighted Average Number of Shares Outstanding, Basic	42,117		40,209		42,086	39,957
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 (2)	0		227