Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Deficit [Member]	Retained Deficit [Member] Cumulative Effect, Period of Adoption, Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance (in shares) at Dec. 31, 2017			40,212,000
Balance at Dec. 31, 2017	$ 223,146		$ 40	$ 426,750	$ (196,316)		$ (7,328)
Net income	234,461		0	0	234,461		0
Foreign currency translation	(4,945)		0	0	0		(4,945)
Interest rate swaps, net of tax	1,276		$ 0	0	0		1,276
Interest rate swap, tax	(425)
Repurchases of common stock, net of retirements (in shares)			(1,291,000)
Repurchases of common stock, net of retirements	(187,469)		$ 0	0	(187,469)		0
Share-based compensation	12,874		$ 0	12,874	0		0
Issuance of stock under share-based compensation plans (in shares)			585,000
Issuance of stock under share-based compensation plans	13,569		$ 0		0		0
Proceeds from stock issued under share-based compensation plans	13,569			13,569
Declaration of cash dividends	(69,322)		$ 0	0	(69,322)		0
Balance (in shares) at Dec. 31, 2018			39,506,000
Balance at Dec. 31, 2018	223,590	$ (709)	$ 40	453,193	(218,646)	$ (709)	(10,997)
Net income	261,575		0	0			0
Foreign currency translation	2,295		0	0	0		2,295
Interest rate swaps, net of tax	(1,657)		$ 0	0	0		(1,657)
Interest rate swap, tax	552
Repurchases of common stock, net of retirements (in shares)			(155,000)
Repurchases of common stock, net of retirements	(23,188)		$ 0	0	(23,188)		0
Share-based compensation	13,472		$ 0	13,472	0		0
Issuance of stock under share-based compensation plans (in shares)			723,000
Issuance of stock under share-based compensation plans	18,574		$ 0		0		0
Proceeds from stock issued under share-based compensation plans	18,574			18,574
Declaration of cash dividends	$ (83,772)		$ 0	0	(83,772)		0
Balance (in shares) at Dec. 31, 2019	40,074,160		40,074,000
Balance at Dec. 31, 2019	$ 410,180		$ 40	485,239	(64,740)		(10,359)
Net income	366,738		0	0	366,738		0
Foreign currency translation	5,210		0	0	0		5,210
Interest rate swaps, net of tax	(8,870)		$ 0	0	0		(8,870)
Interest rate swap, tax	2,957
Repurchases of common stock, net of retirements (in shares)			(401,000)
Repurchases of common stock, net of retirements	(76,199)		$ 0	0	(76,199)		0
Share-based compensation	14,516		$ 0	14,516	0		0
Issuance of stock under share-based compensation plans (in shares)			559,000
Issuance of stock under share-based compensation plans	19,824		$ 0				0
Proceeds from stock issued under share-based compensation plans	19,824			19,824	0
Declaration of cash dividends	$ (91,929)		$ 0	0	(91,929)		0
Balance (in shares) at Dec. 31, 2020	40,232,210		40,232,000
Balance at Dec. 31, 2020	$ 639,470		$ 40	$ 519,579	$ 133,870		$ (14,019)