Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Assets
Investment securities – available for sale	$ 40,590	$ 44,159
Mortgage servicing rights	4,006	3,423
Financial derivatives	849	1,531
Liabilities
Financial derivatives	$ 5,225	$ 4,524
Assets At Fair Value | Assets, Total | Assets
Liabilities
Concentration risk, percentage	10.00%	11.00%
Level 3 Assets | Assets, Total | Assets
Liabilities
Concentration risk, percentage	13.00%	12.00%
Level 3 Assets | Assets | Assets
Liabilities
Concentration risk, percentage	1.00%	1.00%
Liabilities At Fair Value | Liabilities, Total | Liability
Liabilities
Concentration risk, percentage	2.00%	2.00%
Level Three Liabilities | Liabilities, Total | Liability
Liabilities
Concentration risk, percentage	4.00%	4.00%
Level Three Liabilities | Liability | Liability
Liabilities
Concentration risk, percentage	1.00%	1.00%
Fair Value, Recurring
Assets
Investment securities – available for sale	$ 40,590	$ 44,159
Loans	1,244	1,310
Equity investments	2,618	3,147
Trading securities	2,466	1,966
Financial derivatives	3,838	3,768
Other assets	448	432
Total Assets	56,118	59,135
Liabilities
Other borrowed funds	1,042	1,466
Financial derivatives	8,220	7,618
Other liabilities	250	294
Total liabilities	9,512	9,378
Level 1 | Fair Value, Recurring
Assets
Investment securities – available for sale	6,320	8,108
Equity investments	696	1,173
Trading securities	464	798
Financial derivatives	11	16
Other assets	376	352
Total Assets	7,867	10,447
Liabilities
Other borrowed funds	954	1,230
Financial derivatives	14	4
Total liabilities	968	1,234
Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	33,303	35,050
Loans	506	541
Trading securities	2,002	1,168
Financial derivatives	3,821	3,747
Other assets	67	80
Total Assets	40,485	41,240
Liabilities
Other borrowed funds	81	232
Financial derivatives	8,098	7,491
Total liabilities	8,179	7,723
Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	967	1,001
Loans	738	769
Equity investments	1,729	1,778
Financial derivatives	6	5
Other assets	5
Total Assets	7,573	7,252
Liabilities
Other borrowed funds	7	4
Financial derivatives	108	123
Other liabilities	250	294
Total liabilities	365	421
Residential mortgage loans held for sale | Fair Value, Recurring
Assets
Loans held for sale	529	654
Residential mortgage loans held for sale | Level 2 | Fair Value, Recurring
Assets
Loans held for sale	432	411
Residential mortgage loans held for sale | Level 3 | Fair Value, Recurring
Assets
Loans held for sale	97	243
Commercial mortgage loans held for sale | Fair Value, Recurring
Assets
Loans held for sale	379	276
Commercial mortgage loans held for sale | Level 2 | Fair Value, Recurring
Assets
Loans held for sale	354	243
Commercial mortgage loans held for sale | Level 3 | Fair Value, Recurring
Assets
Loans held for sale	25	33
U.S. Treasury and government agencies | Fair Value, Recurring
Assets
Investment securities – available for sale	6,717	8,370
U.S. Treasury and government agencies | Level 1 | Fair Value, Recurring
Assets
Investment securities – available for sale	6,320	8,108
U.S. Treasury and government agencies | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	397	262
Residential mortgage-backed | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	26,899	28,823
Residential mortgage-backed | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	713	819
Residential mortgage-backed | Level 2 | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	26,899	28,823
Residential mortgage-backed | Level 2 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale
Residential mortgage-backed | Level 3 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	713	819
Commercial mortgage servicing rights | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	1,544	1,675
Commercial mortgage servicing rights | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	923	1,256
Commercial mortgage servicing rights | Level 2 | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	1,544	1,675
Commercial mortgage servicing rights | Level 2 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	828	1,253
Commercial mortgage servicing rights | Level 3 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	95	3
Asset-backed | Fair Value, Recurring
Assets
Investment securities – available for sale	1,095	129
Asset-backed | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	992	5
Asset-backed | Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	103	124
Other | Fair Value, Recurring
Assets
Investment securities – available for sale	2,699	3,087
Other | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	2,643	3,032
Other | Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	56	55
Residential mortgage servicing rights | Fair Value, Recurring
Assets
Mortgage servicing rights	2,837	2,310
Residential mortgage servicing rights | Level 3 | Fair Value, Recurring
Assets
Mortgage servicing rights	2,837	2,310
Commercial mortgage servicing rights | Fair Value, Recurring
Assets
Mortgage servicing rights	1,169	1,113
Commercial mortgage servicing rights | Level 3 | Fair Value, Recurring
Assets
Mortgage servicing rights	$ 1,169	$ 1,113