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, 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	79,809			79,809
Other Comprehensive Income (Loss)	(38,141)				(38,141)
Stock issued, including related tax benefits	4,675	1,544	(455)			3,586
Stock issued, including related tax benefits (in shares)		854
Stock-based compensation awards	3,207		3,207
Acquisition of treasury stock (in shares)		(6,421)
Acquisition of treasury stock	(71,337)					(71,337)
Common stock cash dividends	(31,137)			(31,137)
Ending Balance at Jun. 30, 2013	2,028,732	543,637	1,429,019	412,609	(32,466)	(324,067)
Ending Balance (in shares) at Jun. 30, 2013		193,658
Beginning Balance at Dec. 31, 2013	2,063,187	544,568	1,432,974	463,843	(37,341)	(340,857)
Beginning Balance (in shares) at Dec. 31, 2013		192,652
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	81,379			81,379
Other Comprehensive Income (Loss)	28,180				28,180
Stock issued, including related tax benefits	4,070	498	763			2,809
Stock issued, including related tax benefits (in shares)		381
Stock-based compensation awards	3,022		3,022
Acquisition of treasury stock (in shares)		(4,000)
Acquisition of treasury stock	(49,804)					(49,804)
Common stock cash dividends	(30,234)			(30,234)
Ending Balance at Jun. 30, 2014	$ 2,099,800	$ 545,066	$ 1,436,759	$ 514,988	$ (9,161)	$ (387,852)
Ending Balance (in shares) at Jun. 30, 2014		189,033