Consolidated Statements Of Shareholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2010	$ 370,991	$ 685	$ 79,239	$ 285,169	$ 5,898
Beginning Balance (in shares) at Dec. 31, 2010		68,468,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	20,548	3	20,545
Employee stock compensation (in shares)		290,000
Proceeds from stock issuances under employee plans	45,654	22	45,632
Proceeds from stock issuances under employee plans (in shares)		2,280,000
Tax effect of exercise of stock options	23,120		23,120
Cash dividends declared ($1.68 per share, $1.48 per share and $0.90 per share in 2013, 2012, and 2011 respectively)	(61,585)			(61,585)
Repurchase and retirement of common shares	(132,372)	(26)	(3,018)	(129,328)
Repurchase and retirement of common shares (in shares)	(2,608,000)	(2,608,000)
Net income	227,575			227,575
Other comprehensive income	6,125				6,125
Ending Balance at Dec. 31, 2011	500,056	684	165,518	321,831	12,023
Ending Balance (in shares) at Dec. 31, 2011		68,430,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	35,420	2	35,418
Employee stock compensation (in shares)		174,000
Proceeds from stock issuances under employee plans	41,696	17	41,679
Proceeds from stock issuances under employee plans (in shares)		1,692,000
Tax effect of exercise of stock options	29,892		29,892
Cash dividends declared ($1.68 per share, $1.48 per share and $0.90 per share in 2013, 2012, and 2011 respectively)	(101,534)			(101,534)
Repurchase and retirement of common shares	(127,525)	(17)	(3,992)	(123,516)
Repurchase and retirement of common shares (in shares)	(1,649,000)	(1,649,000)
Net income	312,310			312,310
Other comprehensive income	215				215
Ending Balance at Dec. 31, 2012	690,530	686	268,515	409,091	12,238
Ending Balance (in shares) at Dec. 31, 2012		68,647,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Employee stock compensation	57,893	3	57,890
Deferred compensation	(8,421)		(4,358)	(4,063)
Employee stock compensation (in shares)		264,000
Proceeds from stock issuances under employee plans	26,922	10	26,912
Proceeds from stock issuances under employee plans (in shares)		1,049,000
Tax effect of exercise of stock options	28,621		28,621
Cash dividends declared ($1.68 per share, $1.48 per share and $0.90 per share in 2013, 2012, and 2011 respectively)	(113,722)			(113,722)
Repurchase and retirement of common shares	(530,033)	(43)	(16,964)	(513,026)
Repurchase and retirement of common shares (in shares)	(4,337,000)	(4,337,000)
Net income	377,292			377,292
Other comprehensive income	6,523				6,523
Ending Balance at Dec. 31, 2013	$ 535,605	$ 656	$ 360,616	$ 155,572	$ 18,761
Ending Balance (in shares) at Dec. 31, 2013		65,623,000