Quarterly Financial Information (Financial Information By Quarter) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Gross interest income	$ 501,766	$ 490,695	$ 486,952	$ 474,901	$ 473,559	$ 456,230	$ 455,236	$ 448,446	$ 1,954,314	$ 1,833,471	$ 1,853,002
Net interest income	480,470	469,187	464,849	452,842	448,833	425,377	423,704	417,346	1,867,348	1,715,260	1,680,004
Provision for loan losses	(2,687)	18,825	34,492	42,145	22,701	18,262	566	(1,494)	92,775	40,035	(98,082)
Net impairment losses on investment securities									0	0	(27)
Investment securities gains (losses), net	(3,422)	8,480	2,734	(522)	46	3,577	(133,597)	3,114	7,270	(126,860)
Other noninterest income	131,666	136,407	122,983	117,283	118,595	122,367	128,915	114,224	508,339	484,101
Noninterest expense	404,515	403,292	381,894	395,573	397,353	391,280	398,997	392,977	1,585,274	1,580,607	1,649,367
Income before income taxes	206,886	191,957	174,180	131,885	147,420	141,779	19,459	143,201	704,908	451,859	621,423
Net income (loss)	137,401	127,263	113,949	90,437	102,487	100,999	13,960	92,025	469,050	309,471	398,462
Preferred stock dividends	(12,411)	(10,368)	(13,543)	(11,660)	(14,290)	(16,761)	(15,060)	(16,746)	(47,982)	(62,857)	(71,894)
Preferred stock redemption	0	0	(9,759)	0					(9,759)	0	0
Net earnings applicable to common shareholders	$ 124,990	$ 116,895	$ 90,647	$ 78,777	$ 88,197	$ 84,238	$ (1,100)	$ 75,279	$ 411,309	$ 246,614	$ 326,568
Basic, per share	$ 0.61	$ 0.57	$ 0.44	$ 0.38	$ 0.43	$ 0.41	$ (0.01)	$ 0.37	$ 2.00	$ 1.20	$ 1.68
Diluted	$ 0.60	$ 0.57	$ 0.44	$ 0.38	$ 0.43	$ 0.41	$ (0.01)	$ 0.37	$ 1.99	$ 1.20	$ 1.68