Consolidated Statement of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Series E Preferred Stock [Member]	Series D Preferred Stock [Member]	Series F Preferred Stock [Member]	Series A Warrants [Member]	Preferred Stock [Member]	Preferred Stock [Member] Series E Preferred Stock [Member]	Preferred Stock [Member] Series D Preferred Stock [Member]	Preferred Stock [Member] Series F Preferred Stock [Member]	Common Stock [Member]	Common Stock [Member] Series A Warrants [Member]	Common Stock Issuable [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series E Preferred Stock [Member]	Additional Paid-in Capital [Member] Series F Preferred Stock [Member]	Additional Paid-in Capital [Member] Series A Warrants [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss), Net [Member]	Treasury Stock [Member]	Treasury Stock [Member] Series A Warrants [Member]
Beginning 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 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)
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)
Stock-based compensation plans:
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)
Total comprehensive income	1,272,105																1,315,114	(43,009)
Preferred stock cash dividends	(81,270)																(81,270)
Redemption of Series D preferred stock			$ (500,000)					$ (500,000)
Issuance of preferred stock				$ 495,000					$ 500,000						$ (5,000)
Exercise of stock warrants into common stock					$ (2)											$ (4,750)				$ 4,748
Purchases of treasury stock	(641,334)																		$ (641,334)
Stock-based compensation plans:
Compensation expense, net	27,290									169			16,132						10,989
Exercises of stock options, net	169,617									18			(12,190)						181,789
Stock purchase plan	10,594												275						10,319
Directors’ stock plan	2,080									2			535						1,543
Deferred compensation plans, net, including dividend equivalents	3									2		(219)	163				(93)		150
Other	1,015												1,015
Common stock cash dividends - $2.80 per share	(441,765)																(441,765)
Ending balance at Dec. 31, 2016	$ 16,486,622					$ 1,231,500				$ 79,973		$ 2,145	$ 6,676,948				$ 9,222,488	$ (294,636)	$ (431,796)