Quarterly Financial Information (Unaudited) (Financial Information by Quarter) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$ 1,040	$ 1,010	$ 977	$ 920	$ 835	$ 707	$ 608	$ 555	$ 3,947	$ 2,705	$ 2,267
Net interest income	583	585	591	679	720	663	593	544	2,438	2,520	2,208
Provision for credit losses	0	41	46	45	43	71	41	(33)	132	122	(276)
Noninterest income	148	180	189	160	153	165	172	142	677	632	703
Noninterest expense	581	496	508	512	471	479	464	464	2,097	1,878	1,741
Income (loss) before income taxes	150	228	226	282	359	278	260	255	886	1,152	1,446
Net income	126	175	175	204	284	217	203	203	680	907	1,129
Preferred stock dividends	10	7	9	6	7	6	8	8	32	29	29
Net earnings applicable to common shareholders	$ 116	$ 168	$ 166	$ 198	$ 277	$ 211	$ 195	$ 195	$ 648	$ 878	$ 1,100
Net earnings per common share:
Basic (in dollars per share)	$ 0.78	$ 1.13	$ 1.11	$ 1.33	$ 1.84	$ 1.40	$ 1.29	$ 1.27	$ 4.35	$ 5.80	$ 6.80
Diluted (in dollars per share)	$ 0.78	$ 1.13	$ 1.11	$ 1.33	$ 1.84	$ 1.40	$ 1.29	$ 1.27	$ 4.35	$ 5.79	$ 6.79