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, 2010	$ 1,880,389	$ 538,492	$ 1,420,127	$ 158,453	$ 12,495	$ (249,178)
Beginning Balance (in shares) at Dec. 31, 2010		199,050
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	109,494			109,494
Other Comprehensive Income (Loss)	14,416				14,416
Stock issued, including related tax benefits	4,848	1,508	(451)			3,791
Stock issued, including related tax benefits (in shares)		841
Stock-based compensation awards	3,473		3,473
Common stock cash dividends	(27,961)			(27,961)
Ending Balance at Sep. 30, 2011	1,984,659	540,000	1,423,149	239,986	26,911	(245,387)
Ending Balance (in shares) at Sep. 30, 2011		199,891
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)	(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