Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2009	$ 252,187	$ 49	$ 0	$ 202,784	$ 47,128	$ 2,226
Balance (in shares) at Dec. 31, 2009		48,991,000
Net income	57,638	0	0	0	57,638	0
Foreign currency translation	(2,170)	0	0	0	0	(2,170)
Interest rate swaps, net of tax	996	0	0	0	0	996
Repurchases of common stock, net of retirements (in shares)		(638,000)
Repurchases of common stock, net of retirements	(13,683)	0	(2,344)	0	(11,339)	0
Share-based compensation	7,790	0	0	7,790	0	0
Issuance of shares under incentive stock plans (in shares)		925,000
Issuance of shares under incentive stock plans, including tax benefit	8,170	0	0	8,170	0	0
Declaration of cash dividends	(25,746)	0	0	0	(25,746)	0
Balance at Dec. 31, 2010	285,182	49	(2,344)	218,744	67,681	1,052
Balance (in shares) at Dec. 31, 2010		49,278,000
Net income	71,993	0	0	0	71,993	0
Foreign currency translation	(609)	0	0	0	0	(609)
Interest rate swaps, net of tax	1,777	0	0	0	0	1,777
Repurchases of common stock, net of retirements (in shares)		(3,034,000)
Repurchases of common stock, net of retirements	(76,564)	(3)	2,344	0	(78,905)	0
Share-based compensation	8,233	0	0	8,233	0	0
Issuance of shares under incentive stock plans (in shares)		1,123,000
Issuance of shares under incentive stock plans, including tax benefit	16,204	1	0	16,203	0	0
Declaration of cash dividends	(26,470)	0	0	0	(26,470)	0
Balance at Dec. 31, 2011	279,746	47	0	243,180	34,299	2,220
Balance (in shares) at Dec. 31, 2011	47,366,997	47,367,000
Net income	81,972	0	0	0	81,972	0
Foreign currency translation	(534)	0	0	0	0	(534)
Interest rate swaps, net of tax	(1,820)	0	0	0	0	(1,820)
Repurchases of common stock, net of retirements (in shares)		(2,165,000)
Repurchases of common stock, net of retirements	(81,761)	(2)	0	0	(81,759)	0
Share-based compensation	8,465	0	0	8,465	0	0
Issuance of shares under incentive stock plans (in shares)		1,102,000
Issuance of shares under incentive stock plans, including tax benefit	24,690	1	0	24,689	0	0
Declaration of cash dividends	(29,135)	0	0	0	(29,135)	0
Balance at Dec. 31, 2012	$ 281,623	$ 46	$ 0	$ 276,334	$ 5,377	$ (134)
Balance (in shares) at Dec. 31, 2012	46,303,728	46,304,000