Consolidated Statements Of Shareholder's 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, 2011		$ 3,859,631	$ 0	$ 168,468	$ 425,331	$ 549,916	$ 3,208,555	$ (492,639)
Comprehensive income (loss)		904,683				375,359	529,324
Common dividends declared ($.40 in 2012, $.45 in 2013, and $.51 in 2014 a share)	[1]	(57,592)					(57,592)
Acquisition of treasury stock		(570,165)						(570,165)
Stock-based compensation		21,605			18,413			3,192
Exercise of stock options		203,624			22,602		(51,322)	232,344
Retirement of treasury stock	[1]	0		(9,750)	(26,564)		(278,533)	314,847
Ending Balance at Dec. 31, 2012		4,361,786	0	158,718	439,782	925,275	3,350,432	(512,421)
Comprehensive income (loss)		(185,822)				(714,294)	528,472
Common dividends declared ($.40 in 2012, $.45 in 2013, and $.51 in 2014 a share)	[1]	(61,991)					(61,991)
Acquisition of treasury stock		(482,264)						(482,264)
Stock-based compensation		25,642			23,464		563	1,615
Exercise of stock options		118,991			21,315		(25,195)	122,871
Retirement of treasury stock	[1]	0		(7,500)	(22,503)		(296,748)	326,751
Ending Balance at Dec. 31, 2013		3,776,342	0	151,218	462,058	210,981	3,495,533	(543,448)
Comprehensive income (loss)		1,329,410				786,471	542,939
Common dividends declared ($.40 in 2012, $.45 in 2013, and $.51 in 2014 a share)		(65,998)					(65,998)
Acquisition of treasury stock		(449,308)						(449,308)
Stock-based compensation		32,203			31,315		362	526
Exercise of stock options		74,817			18,524		(22,641)	78,934
Retirement of treasury stock		0		(17,000)	(54,284)		(573,349)	644,633
Ending Balance at Dec. 31, 2014		$ 4,697,466	$ 0	$ 134,218	$ 457,613	$ 997,452	$ 3,376,846	$ (268,663)

[1] Dollar and per share amounts have been retrospectively adjusted to give effect to the stock split described in Note 1.