Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2022	Dec. 31, 2021
Assets
Investment securities – available for sale	$ 112,313	$ 131,536
Mortgage servicing rights	2,208	1,818
Financial derivatives	4,005	3,620
Liabilities
Financial derivatives	$ 2,913	$ 985
Assets At Fair Value \| Assets, Total \| Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	24.00%	26.00%
Level 3 Assets \| Assets, Total \| Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	5.00%	4.00%
Level 3 Assets \| Assets \| Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	1.00%	1.00%
Liabilities At Fair Value \| Liabilities, Total \| Liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	2.00%	1.00%
Level Three Liabilities \| Liabilities, Total \| Liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	5.00%	10.00%
Level Three Liabilities \| Liability \| Liability
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	1.00%	1.00%
Fair Value, Recurring
Assets
Investment securities – available for sale	$ 112,313	$ 131,536
Loans	1,395	1,501
Equity investments	2,807	3,231
Trading securities	2,395	1,851
Financial derivatives	5,935	5,152
Other assets	491	518
Total Assets	128,890	147,484
Liabilities
Other borrowed funds	1,235	773
Financial derivatives	6,963	3,570
Other liabilities	158	175
Total liabilities	8,356	4,518
Level 1 \| Fair Value, Recurring
Assets
Investment securities – available for sale	33,016	41,873
Equity investments	876	1,373
Trading securities	651	250
Financial derivatives	5	5
Other assets	391	404
Total Assets	34,939	43,905
Liabilities
Other borrowed funds	1,179	725
Financial derivatives	5
Total liabilities	1,184	725
Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	78,057	88,331
Loans	544	617
Trading securities	1,744	1,601
Financial derivatives	5,920	5,109
Other assets	100	114
Total Assets	87,558	97,519
Liabilities
Other borrowed funds	53	45
Financial derivatives	6,724	3,285
Total liabilities	6,777	3,330
Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,240	1,332
Loans	851	884
Equity investments	1,751	1,680
Financial derivatives	10	38
Total Assets	6,213	5,882
Liabilities
Other borrowed funds	3	3
Financial derivatives	234	285
Other liabilities	158	175
Total liabilities	395	463
Residential mortgage loans held for sale \| Fair Value, Recurring
Assets
Loans held for sale	1,039	1,302
Residential mortgage loans held for sale \| Level 2 \| Fair Value, Recurring
Assets
Loans held for sale	931	1,221
Residential mortgage loans held for sale \| Level 3 \| Fair Value, Recurring
Assets
Loans held for sale	108	81
Commercial mortgage loans held for sale \| Fair Value, Recurring
Assets
Loans held for sale	307	575
Commercial mortgage loans held for sale \| Level 2 \| Fair Value, Recurring
Assets
Loans held for sale	262	526
Commercial mortgage loans held for sale \| Level 3 \| Fair Value, Recurring
Assets
Loans held for sale	45	49
U.S. Treasury and government agencies \| Fair Value, Recurring
Assets
Investment securities – available for sale	35,221	46,164
U.S. Treasury and government agencies \| Level 1 \| Fair Value, Recurring
Assets
Investment securities – available for sale	33,016	41,873
U.S. Treasury and government agencies \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	2,205	4,291
Residential mortgage-backed \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	58,815	67,632
Residential mortgage-backed \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,332	1,158
Residential mortgage-backed \| Level 2 \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	58,815	67,632
Residential mortgage-backed \| Level 2 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	313	61
Residential mortgage-backed \| Level 3 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,019	1,097
Commercial mortgage-backed \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	2,110	1,773
Commercial mortgage-backed \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	3,455	3,436
Commercial mortgage-backed \| Level 2 \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	2,110	1,773
Commercial mortgage-backed \| Level 2 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	3,452	3,433
Commercial mortgage-backed \| Level 3 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	3	3
Asset-backed \| Fair Value, Recurring
Assets
Investment securities – available for sale	6,305	6,409
Asset-backed \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	6,153	6,246
Asset-backed \| Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	152	163
Other \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,075	4,964
Other \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,009	4,895
Other \| Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	66	69
Residential mortgage servicing rights \| Fair Value, Recurring
Assets
Mortgage servicing rights	1,322	1,078
Residential mortgage servicing rights \| Level 3 \| Fair Value, Recurring
Assets
Mortgage servicing rights	1,322	1,078
Commercial mortgage servicing rights \| Fair Value, Recurring
Assets
Mortgage servicing rights	886	740
Commercial mortgage servicing rights \| Level 3 \| Fair Value, Recurring
Assets
Mortgage servicing rights	$ 886	$ 740

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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