Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Assets
Investment securities – available for sale	$ 60,338	$ 41,785
Mortgage servicing rights	3,503	3,686
Financial derivatives	1,116	897
Liabilities
Financial derivatives	2,360	3,538
Other liabilities	$ 100	$ 100
Assets At Fair Value | Assets, Total | Assets
Liabilities
Concentration risk, percentage	13.00%	10.00%
Level 3 Assets | Assets, Total | Assets
Liabilities
Concentration risk, percentage	10.00%	13.00%
Level 3 Assets | Assets | Assets
Liabilities
Concentration risk, percentage	1.00%	1.00%
Liabilities At Fair Value | Liabilities, Total | Liability
Liabilities
Concentration risk, percentage	1.00%	1.00%
Level Three Liabilities | Liabilities, Total | Liability
Liabilities
Concentration risk, percentage	7.00%	6.00%
Level Three Liabilities | Liability | Liability
Liabilities
Concentration risk, percentage	1.00%	1.00%
Fair Value, Recurring
Assets
Investment securities – available for sale	$ 60,338	$ 41,785
Loans	1,173	1,238
Equity investments	3,242	2,717
Trading securities	2,967	2,799
Financial derivatives	3,308	3,429
Other assets	575	496
Total Assets	75,841	56,862
Liabilities
Other borrowed funds	1,553	817
Financial derivatives	4,627	5,899
Other liabilities	176	237
Total liabilities	6,356	6,953
Level 1 | Fair Value, Recurring
Assets
Investment securities – available for sale	21,584	6,292
Equity investments	976	574
Trading securities	1,000	377
Financial derivatives	21	29
Other assets	453	403
Total Assets	24,034	7,675
Liabilities
Other borrowed funds	1,383	724
Financial derivatives	6	11
Total liabilities	1,389	735
Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	37,873	34,537
Loans	489	512
Trading securities	1,967	2,422
Financial derivatives	3,275	3,394
Other assets	114	85
Total Assets	44,379	41,548
Liabilities
Other borrowed funds	162	84
Financial derivatives	4,340	5,736
Total liabilities	4,502	5,820
Level 3
Assets
Equity investments	2,063	1,952
Liabilities
Financial derivatives	276	145
Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	881	956
Loans	684	726
Equity investments	2,063	1,952
Financial derivatives	12	6
Other assets	8	8
Total Assets	7,225	7,448
Liabilities
Other borrowed funds	8	9
Financial derivatives	281	152
Other liabilities	176	237
Total liabilities	465	398
Residential mortgage loans held for sale | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	658	474
Residential mortgage loans held for sale | Level 2 | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	588	371
Residential mortgage loans held for sale | Level 3 | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	70	103
Commercial mortgage loans held for sale | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	77	238
Commercial mortgage loans held for sale | Level 2 | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	73	227
Commercial mortgage loans held for sale | Level 3 | Fair Value, Recurring
Assets
Commercial mortgage loans held for sale	4	11
U.S. Treasury and government agencies | Fair Value, Recurring
Assets
Investment securities – available for sale	22,639	6,951
U.S. Treasury and government agencies | Level 1 | Fair Value, Recurring
Assets
Investment securities – available for sale	21,584	6,292
U.S. Treasury and government agencies | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	1,055	659
Residential mortgage-backed | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	29,661	27,880
Residential mortgage-backed | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	628	696
Residential mortgage-backed | Level 2 | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	29,661	27,880
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	628	696
Commercial mortgage servicing rights | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	1,892	1,546
Commercial mortgage servicing rights | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	734	869
Commercial mortgage servicing rights | Level 2 | Mortgage-backed Securities Agency | Fair Value, Recurring
Assets
Investment securities – available for sale	1,892	1,546
Commercial mortgage servicing rights | Level 2 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	631	766
Commercial mortgage servicing rights | Level 3 | Mortgage-backed Securities Non-agency | Fair Value, Recurring
Assets
Investment securities – available for sale	103	103
Asset-backed | Fair Value, Recurring
Assets
Investment securities – available for sale	2,289	1,116
Asset-backed | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	2,193	1,014
Asset-backed | Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	96	102
Other | Fair Value, Recurring
Assets
Investment securities – available for sale	2,495	2,727
Other | Level 2 | Fair Value, Recurring
Assets
Investment securities – available for sale	2,441	2,672
Other | Level 3 | Fair Value, Recurring
Assets
Investment securities – available for sale	54	55
Residential mortgage servicing rights | Fair Value, Recurring
Assets
Mortgage servicing rights	2,528	2,654
Residential mortgage servicing rights | Level 3 | Fair Value, Recurring
Assets
Mortgage servicing rights	2,528	2,654
Commercial mortgage servicing rights | Fair Value, Recurring
Assets
Mortgage servicing rights	975	1,032
Commercial mortgage servicing rights | Level 3 | Fair Value, Recurring
Assets
Mortgage servicing rights	$ 975	$ 1,032