Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	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, 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:
Total comprehensive income	1,314,585												1,138,480	176,105
Preferred stock cash dividends	(53,450)												(53,450)
Exercise of stock warrants into common stock						$ 93	13			$ (93)	(13)
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)
Exercise of stock warrants into common stock							85				(85)
Stock-based compensation plans:
Total comprehensive income	949,411												1,066,246	(116,835)
Preferred stock cash dividends	(75,878)												(75,878)
Exercise of stock warrants into common stock							85				(85)
Issuance of Series E preferred stock		$ 346,500		$ 350,000								$ (3,500)
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)
Total comprehensive income	1,009,034												1,079,667	(70,633)
Preferred stock cash dividends	(81,270)												(81,270)
Exercise of stock warrants into common stock							1				(1)
Stock-based compensation plans:
Total comprehensive income	1,009,034												1,079,667	(70,633)
Acquisition of Hudson City Bancorp, Inc, common stock issued	3,110,581				12,977				3,097,604
Acquisition of Hudson City Bancorp, Inc, common stock awards converted	28,243								28,243
Preferred stock cash dividends	(81,270)												(81,270)
Exercise of stock warrants into common stock							$ 1				$ (1)
Compensation expense, net	43,195				155				43,040
Exercises of stock options, net	88,893				438				88,455
Stock purchase plan	10,346				45				10,301
Directors' stock plan	1,761				7				1,754
Deferred compensation plans, net, including dividend equivalents	(51)				2			(244)	293				(102)
Other	1,573								1,573
Common stock cash dividends - $2.80 per share	(374,912)												(374,912)
Ending Balance at Dec. 31, 2015	$ 16,173,289		$ 1,231,500		$ 79,782			$ 2,364	$ 6,680,768				$ 8,430,502	$ (251,627)