Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2010	$ 3,667,329	$ 0	$ 119,812	$ 432,608	$ 23,092	$ 3,124,436	$ (32,619)
Comprehensive income (loss)	1,023,985				526,824	497,161
Common dividends declared ($0.46 in 2011, $.60 in 2012 and $.68 in 2013 a share)	(49,815)					(49,815)
Acquisition of treasury stock	(972,556)						(972,556)
Stock-based compensation	14,954			7,631			7,323
Exercise of stock options	175,734			13,121		(29,328)	191,941
Retirement of treasury stock	0		(7,500)	(28,029)		(277,743)	313,272
Ending Balance at Dec. 31, 2011	3,859,631	0	112,312	425,331	549,916	3,264,711	(492,639)
Comprehensive income (loss)	904,683				375,359	529,324
Common dividends declared ($0.46 in 2011, $.60 in 2012 and $.68 in 2013 a share)	(57,592)					(57,592)
Acquisition of treasury stock	(570,165)						(570,165)
Stock-based compensation	21,605			18,413			3,192
Exercise of stock options	203,624			22,602		(51,322)	232,344
Retirement of treasury stock	0		(6,500)	(26,564)		(281,783)	314,847
Ending Balance at Dec. 31, 2012	4,361,786	0	105,812	439,782	925,275	3,403,338	(512,421)
Comprehensive income (loss)	(185,822)				(714,294)	528,472
Common dividends declared ($0.46 in 2011, $.60 in 2012 and $.68 in 2013 a share)	(61,991)					(61,991)
Acquisition of treasury stock	(482,264)						(482,264)
Stock-based compensation	25,642			23,464		563	1,615
Exercise of stock options	118,991			21,315		(25,195)	122,871
Retirement of treasury stock	0		(5,000)	(22,503)		(299,248)	326,751
Ending Balance at Dec. 31, 2013	$ 3,776,342	$ 0	$ 100,812	$ 462,058	$ 210,981	$ 3,545,939	$ (543,448)