Financial Information By Quarter (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Gross interest income	$ 647	$ 677	$ 684	$ 675	$ 656	$ 631	$ 606	$ 588	$ 2,683	$ 2,481	$ 2,192
Net Interest Income	559	567	569	577	576	565	548	541	2,272	2,230	2,065
Provision for loan losses									37	39	24
Noninterest Income	152	146	132	132	140	136	138	138	562	552	544
Noninterest expense	472	415	424	431	420	420	421	418	1,742	1,679	1,656
Income before income taxes	235	288	256	274	290	292	253	308	1,053	1,143	936
Net income	183	222	198	213	226	223	197	238	816	884	592
Other Preferred Stock Dividends and Adjustments	(9)	(8)	(9)	(8)	(9)	(8)	(10)	(7)	(34)	(34)	(40)
Preferred stock redemption									0	0	(2)
Net earnings applicable to common shareholders	$ 174	$ 214	$ 189	$ 205	$ 217	$ 215	$ 187	$ 231	$ 782	$ 850	$ 550
Basic, per share	$ 1.03	$ 1.23	$ 1.05	$ 1.10	$ 1.14	$ 1.11	$ 0.95	$ 1.16	$ 4.41	$ 4.36	$ 2.71
Diluted	$ 0.97	$ 1.17	$ 0.99	$ 1.03	$ 1.08	$ 1.04	$ 0.88	$ 1.08	$ 4.16	$ 4.08	$ 2.60
Provision for Credit Losses	$ 4	$ 10	$ 21	$ 4	$ 6	$ 11	$ 12	$ 47	$ 39	$ 40	$ 17