Consolidated Statements Of Stockholders' Equity (USD $) In Thousands, except Share data	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income/(Loss) [Member]	Total
Beginning balance at Dec. 31, 2009	$ 1,161	$ 336,059	$ 303,655	$ 13,545	$ 654,420
Beginning balance, shares at Dec. 31, 2009	116,051,811
Net income			109,116		109,116
Other comprehensive income (loss)				(14,255)	(14,255)
Issuance of common stock under employee plans, including tax benefits	38	51,814			51,852
Issuance of common stock under employee plans, including tax benefits, shares	3,788,994
Stock-based compensation		18,897			18,897
Repurchase and retirement of common stock	(21)	(6,051)	(35,790)		(41,862)
Repurchase and retirement of common stock, shares	(2,089,098)				2,089,098
Business acquisition	1	2,998			2,999
Business acquisition, shares	153,268
Dividends paid			(40,618)		(40,618)
Disqualified dispositions		3,996			3,996
Ending balance at Dec. 31, 2010	1,179	407,713	336,363	(710)	744,545
Ending balance, shares at Dec. 31, 2010	117,904,975
Net income			94,072		94,072
Other comprehensive income (loss)				(2,790)	(2,790)
Issuance of common stock under employee plans, including tax benefits	27	32,878			32,905
Issuance of common stock under employee plans, including tax benefits, shares	2,715,253
Stock-based compensation		23,106			23,106
Repurchase and retirement of common stock, shares					0
Business acquisition	1	1,813			1,814
Business acquisition, shares	56,915
Dividends paid			(47,961)		(47,961)
Disqualified dispositions		6,320			6,320
Ending balance at Dec. 31, 2011	1,207	471,830	382,474	(3,500)	852,011
Ending balance, shares at Dec. 31, 2011	120,677,143				120,677,143
Net income			90,137		90,137
Other comprehensive income (loss)				4,344	4,344
Issuance of common stock under employee plans, including tax benefits	22	30,879			30,901
Issuance of common stock under employee plans, including tax benefits, shares	2,201,547
Stock-based compensation		27,679			27,679
Repurchase and retirement of common stock, shares					0
Dividends paid			(68,401)		(68,401)
Disqualified dispositions		2,457			2,457
Ending balance at Dec. 31, 2012	$ 1,229	$ 532,845	$ 404,210	$ 844	$ 939,128
Ending balance, shares at Dec. 31, 2012	122,878,690				122,878,690