Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2014	$ 7,369,530	$ 1,004,011	$ 4,723,855	$ 1,769,705	$ (128,041)
Balance (in shares) at Dec. 31, 2014			203,014,903
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	206,984			206,984
Other comprehensive income, net of tax	111,066				111,066
Subordinated debt converted to preferred stock	104	148	$ (44)
Net activity under employee plans and related tax benefits	32,477		$ 32,477
Net activity under employee plans and related tax benefits, shares			1,263,691
Dividends on preferred stock	(48,567)			(48,567)
Dividends on common stock	(32,785)			(32,785)
Change in deferred compensation	(714)			(714)
Balance at Sep. 30, 2015	7,638,095	1,004,159	$ 4,756,288	1,894,623	(16,975)
Balance (in shares) at Sep. 30, 2015			204,278,594
Preferred Stock Redemption In Period	(126,144)	(118,889)	$ 2,504	(9,759)
Stock Repurchased and Retired During Period, Value	(45,029)		$ (45,029)
Stock Repurchased During Period, Shares			(1,468,800)
Balance at Dec. 31, 2015	$ 7,507,519	828,490	$ 4,766,731	1,966,910	(54,612)
Balance (in shares) at Dec. 31, 2015	204,417,093		204,417,093
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income for the period	$ 331,649			331,649
Other comprehensive income, net of tax	64,613				64,613
Net activity under employee plans and related tax benefits	23,706		$ 23,706
Net activity under employee plans and related tax benefits, shares			901,779
Dividends on preferred stock	(35,571)			(35,571)
Dividends on common stock	(41,298)			(41,298)
Change in deferred compensation	(138)			(138)
Balance at Sep. 30, 2016	$ 7,679,307	$ 709,601	$ 4,747,912	$ 2,211,793	$ 10,001
Balance (in shares) at Sep. 30, 2016	203,850,072		203,850,072