Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balances at Dec. 31, 2009	$ 457,316	$ 231	$ 54,361	$ 407,933	$ (5,209)
Net income	78,716			78,716
Foreign currency translation adjustment, net of tax expense (benefit) of $1,035 in 2012, ($1,447) in 2011 and ($599) in 2010	1,095				1,095
Comprehensive income	79,811
Exercise of stock options	254		254
Tax benefit from stock based compensation	801		801
Stock granted under restricted stock plan, net	79		79
Stock based compensation	3,192		3,192
Shares repurchased and retired	(1,212)		(1,212)
Shares surrendered by employees to pay taxes	(692)			(692)
Cash dividends, per share $1.02 in 2012, $0.88 in 2011 and $0.76 in 2010	(17,570)			(17,570)
Balances at Dec. 31, 2010	521,979	231	57,475	468,387	(4,114)
Net income	130,136			130,136
Foreign currency translation adjustment, net of tax expense (benefit) of $1,035 in 2012, ($1,447) in 2011 and ($599) in 2010	249				249
Comprehensive income	130,385
Exercise of stock options	76		76
Tax benefit from stock based compensation	1,412		1,412
Stock granted under restricted stock plan, net	223		223
Stock based compensation	4,002		4,002
Shares repurchased and retired	(6,649)		(6,649)
Shares surrendered by employees to pay taxes	(901)			(901)
Cash dividends, per share $1.02 in 2012, $0.88 in 2011 and $0.76 in 2010	(20,369)			(20,369)
Balances at Dec. 31, 2011	630,158	231	56,539	577,253	(3,865)
Net income	105,933			105,933
Foreign currency translation adjustment, net of tax expense (benefit) of $1,035 in 2012, ($1,447) in 2011 and ($599) in 2010	1,925				1,925
Comprehensive income	107,858
Exercise of stock options	54		54
Tax benefit from stock based compensation	1,388		1,388
Stock granted under restricted stock plan, net	207	1	206
Stock based compensation	4,903		4,903
Shares repurchased and retired	(5,727)	(1)	(5,726)
Shares surrendered by employees to pay taxes	(2,200)			(2,200)
Cash dividends, per share $1.02 in 2012, $0.88 in 2011 and $0.76 in 2010	(23,563)			(23,563)
Balances at Dec. 31, 2012	$ 713,078	$ 231	$ 57,364	$ 657,423	$ (1,940)