Consolidated Statements of Shareholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Share Repurchase Program [Member]	Accelerated Stock Repurchase Program [Member]	Common Stock [Member]	Common Stock [Member] Share Repurchase Program [Member]	Common Stock [Member] Accelerated Stock Repurchase Program [Member]	Additional Paid-In Capital [Member]	Additional Paid-In Capital [Member] Accelerated Stock Repurchase Program [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Treasury Stock [Member] Share Repurchase Program [Member]	Treasury Stock [Member] Accelerated Stock Repurchase Program [Member]
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 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
Beginning Balance at Dec. 31, 2014	1,996,665			$ 545,555			1,420,523		558,810	(17,722)	(510,501)
Beginning Balance (in shares) at Dec. 31, 2014				178,924
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income	76,716								76,716
Other comprehensive loss	(5,155)									(5,155)
Stock issued, including related tax benefits	4,695			$ 664			1,954				2,077
Stock issued, including related tax benefits (in shares)				423
Stock-based compensation awards	$ 2,838						2,838
Acquisition of treasury stock (in shares)	(1,500)				(1,538)	(1,790)
Acquisition of treasury stock		$ (19,013)	$ 0					$ 20,000				$ (19,013)	$ (20,000)
Common stock cash dividends	$ (31,929)								(31,929)
Ending Balance at Jun. 30, 2015	$ 2,024,817			$ 546,219			$ 1,445,315		$ 603,597	$ (22,877)	$ (547,437)
Ending Balance (in shares) at Jun. 30, 2015				176,019