Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2011	$ 1,992,539	$ 540,386	$ 1,423,727	$ 264,059	$ 7,955	$ (243,588)
Beginning Balance (in shares) at Dec. 31, 2011		200,164
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	119,605			119,605
Other Comprehensive Income (Loss)	3,852				3,852
Stock issued, including related tax benefits	5,110	1,434	(1,889)			5,565
Stock issued, including related tax benefits (in shares)		926
Stock-based compensation awards	3,963		3,963
Acquisition of treasury stock (in shares)		(2,115)
Acquisition of treasury stock	(20,360)					(20,360)
Common stock cash dividends	(44,026)			(44,026)
Ending Balance at Sep. 30, 2012	2,060,683	541,820	1,425,801	339,638	11,807	(258,383)
Ending Balance (in shares) at Sep. 30, 2012		198,975
Beginning Balance at Dec. 31, 2012	2,081,656	542,093	1,426,267	363,937	5,675	(256,316)
Beginning Balance (in shares) at Dec. 31, 2012		199,225
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	119,757			119,757
Other Comprehensive Income (Loss)	(46,546)				(46,546)
Stock issued, including related tax benefits	7,359	1,959	562			4,838
Stock issued, including related tax benefits (in shares)		1,107
Stock-based compensation awards	4,186		4,186
Acquisition of treasury stock (in shares)	(8,000)	(8,000)
Acquisition of treasury stock	(90,927)					(90,927)
Common stock cash dividends	(46,521)			(46,521)
Ending Balance at Sep. 30, 2013	$ 2,028,964	$ 544,052	$ 1,431,015	$ 437,173	$ (40,871)	$ (342,405)
Ending Balance (in shares) at Sep. 30, 2013		192,332