Consolidated Statement of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Series E Preferred Stock [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series E Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Series C Stock Warrants [Member]	Common Stock [Member] Series A Warrants [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series C Stock Warrants [Member]	Additional Paid-in Capital [Member] Series A Warrants [Member]	Additional Paid-in Capital [Member] Series E Preferred Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]
Beginning Balance at Dec. 31, 2011	$ 9,271,209		$ 864,585		$ 62,842			$ 4,072	$ 2,828,986				$ 5,867,165	$ (356,441)
Total comprehensive income	1,145,675												1,029,498	116,177
Preferred stock cash dividends	(53,450)												(53,450)
Amortization of preferred stock discount			7,915										(7,915)
Stock-based compensation plans:
Compensation expense, net	48,166				229				47,937
Exercises of stock options, net	135,945				928				135,017
Stock purchase plan	10,117				75				10,042
Directors' stock plan	1,480				9				1,471
Deferred compensation plans, net, including dividend equivalents	(161)				5			(599)	593				(160)
Other	1,474								1,474
Common stock cash dividends - $2.80 per share	(357,862)												(357,862)
Ending Balance at Dec. 31, 2012	10,202,593		872,500		64,088			3,473	3,025,520				6,477,276	(240,264)
Total comprehensive income	1,314,585												1,138,480	176,105
Preferred stock cash dividends	(53,450)												(53,450)
Amortization of preferred stock discount			9,000										(9,000)
Exercise of stock warrants into common stock						93	13			(93)	(13)
Stock-based compensation plans:
Compensation expense, net	38,027				137				37,890
Exercises of stock options, net	164,805				914				163,891
Directors' stock plan	1,644				8				1,636
Deferred compensation plans, net, including dividend equivalents	(109)				5			(558)	575				(131)
Other	2,608								2,608
Common stock cash dividends - $2.80 per share	(365,171)												(365,171)
Ending Balance at Dec. 31, 2013	11,305,532		881,500		65,258			2,915	3,232,014				7,188,004	(64,159)
Total comprehensive income	949,411												1,066,246	(116,835)
Preferred stock cash dividends	(75,878)												(75,878)
Issuance of Series E preferred stock		346,500		350,000								(3,500)
Exercise of stock warrants into common stock							85				(85)
Stock-based compensation plans:
Compensation expense, net	45,434				128				45,306
Exercises of stock options, net	123,109				633				122,476
Stock purchase plan	9,588				43				9,545
Directors' stock plan	1,665				7				1,658
Deferred compensation plans, net, including dividend equivalents	(75)				3			(307)	345				(116)
Other	1,747								1,747
Common stock cash dividends - $2.80 per share	(371,137)												(371,137)
Ending Balance at Dec. 31, 2014	$ 12,335,896		$ 1,231,500		$ 66,157			$ 2,608	$ 3,409,506				$ 7,807,119	$ (180,994)