Quarterly Financial Information (Unaudited) (Financial Information by Quarter) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Quarterly Financial Information Disclosure [Abstract]
Gross interest income	$ 566	$ 569	$ 570	$ 562	$ 571	$ 581	$ 595	$ 622	$ 2,267	$ 2,368	$ 2,683
Net interest income	553	555	555	545	550	555	563	548	2,208	2,216	2,272
Provision for credit losses	25	(46)	(123)	(132)	(67)	55	168	258	(276)	414	39
Noninterest income	190	139	205	169	166	157	117	134	703	574	562
Noninterest expense	449	429	428	435	424	442	430	408	1,741	1,704	1,742
Income before income taxes	269	311	455	411	359	215	82	16	1,446	672	1,053
Net income	213	240	354	322	284	175	66	14	1,129	539	816
Preferred stock dividends	6	6	9	8	9	8	9	8	29	34	34
Net earnings applicable to common shareholders	$ 207	$ 234	$ 345	$ 314	$ 275	$ 167	$ 57	$ 6	$ 1,100	$ 505	$ 782
Net earnings per common share:
Basic (in dollars per share)	$ 1.34	$ 1.45	$ 2.08	$ 1.90	$ 1.66	$ 1.01	$ 0.34	$ 0.04	$ 6.80	$ 3.06	$ 4.41
Diluted (in dollars per share)	$ 1.34	$ 1.45	$ 2.08	$ 1.90	$ 1.66	$ 1.01	$ 0.34	$ 0.04	$ 6.79	$ 3.02	$ 4.16