Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Assets
Investment securities – available for sale	$ 125,058	$ 87,358
Mortgage servicing rights	1,793	1,242
Financial derivatives	4,669	4,379
Liabilities
Financial derivatives	$ 722	$ 584
Assets At Fair Value \| Assets, Total \| Assets
Liabilities
Concentration risk, percentage	26.00%	22.00%
Level 3 Assets \| Assets, Total \| Assets
Liabilities
Concentration risk, percentage	4.00%	5.00%
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%	9.00%
Level Three Liabilities \| Liability \| Liability
Liabilities
Concentration risk, percentage	1.00%	1.00%
Fair Value, Recurring
Assets
Investment securities – available for sale	$ 125,058	$ 87,358
Loans	1,727	1,365
Equity investments	2,697	2,629
Trading securities	1,829	2,238
Financial derivatives	6,447	6,533
Other assets	554	454
Total Assets	142,065	103,035
Liabilities
Other borrowed funds	810	707
Financial derivatives	3,719	2,756
Other liabilities	124	43
Total liabilities	4,653	3,506
Level 1 \| Fair Value, Recurring
Assets
Investment securities – available for sale	34,627	16,675
Equity investments	922	1,070
Trading securities	621	548
Financial derivatives	3
Other assets	450	373
Total Assets	36,623	18,666
Liabilities
Other borrowed funds	732	661
Total liabilities	732	661
Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	88,935	69,036
Loans	748	718
Trading securities	1,208	1,690
Financial derivatives	6,357	6,415
Other assets	104	81
Total Assets	98,902	78,936
Liabilities
Other borrowed funds	76	44
Financial derivatives	3,519	2,483
Total liabilities	3,595	2,527
Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,496	1,647
Loans	979	647
Equity investments	1,540	1,263
Financial derivatives	87	118
Total Assets	6,305	5,137
Liabilities
Other borrowed funds	2	2
Financial derivatives	200	273
Other liabilities	124	43
Total liabilities	326	318
Residential mortgage loans held for sale \| Fair Value, Recurring
Assets
Loans held for sale	1,504	854
Residential mortgage loans held for sale \| Level 2 \| Fair Value, Recurring
Assets
Loans held for sale	1,385	691
Residential mortgage loans held for sale \| Level 3 \| Fair Value, Recurring
Assets
Loans held for sale	119	163
Commercial mortgage loans held for sale \| Fair Value, Recurring
Assets
Loans held for sale	217	362
Commercial mortgage loans held for sale \| Level 2 \| Fair Value, Recurring
Assets
Loans held for sale	165	305
Commercial mortgage loans held for sale \| Level 3 \| Fair Value, Recurring
Assets
Loans held for sale	52	57
Other consumer loans held for sale \| Fair Value, Recurring
Assets
Loans held for sale	239
Other consumer loans held for sale \| Level 3 \| Fair Value, Recurring
Assets
Loans held for sale	239
U.S. Treasury and government agencies \| Fair Value, Recurring
Assets
Investment securities – available for sale	39,011	20,711
U.S. Treasury and government agencies \| Level 1 \| Fair Value, Recurring
Assets
Investment securities – available for sale	34,627	16,675
U.S. Treasury and government agencies \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	4,384	4,036
Residential mortgage-backed \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	67,314	48,911
Residential mortgage-backed \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,323	1,501
Residential mortgage-backed \| Level 2 \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	67,314	48,911
Residential mortgage-backed \| Level 2 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	86	136
Residential mortgage-backed \| Level 3 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	1,237	1,365
Commercial mortgage-backed \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	2,331	2,688
Commercial mortgage-backed \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	4,079	3,689
Commercial mortgage-backed \| Level 2 \| Mortgage-backed Securities Agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	2,331	2,688
Commercial mortgage-backed \| Level 2 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	4,068	3,678
Commercial mortgage-backed \| Level 3 \| Mortgage-backed Securities Non-agency \| Fair Value, Recurring
Assets
Investment securities – available for sale	11	11
Asset-backed \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,697	5,150
Asset-backed \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,522	4,951
Asset-backed \| Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	175	199
Other \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,303	4,708
Other \| Level 2 \| Fair Value, Recurring
Assets
Investment securities – available for sale	5,230	4,636
Other \| Level 3 \| Fair Value, Recurring
Assets
Investment securities – available for sale	73	72
Residential mortgage servicing rights \| Fair Value, Recurring
Assets
Mortgage servicing rights	1,111	673
Residential mortgage servicing rights \| Level 3 \| Fair Value, Recurring
Assets
Mortgage servicing rights	1,111	673
Commercial mortgage servicing rights \| Fair Value, Recurring
Assets
Mortgage servicing rights	682	569
Commercial mortgage servicing rights \| Level 3 \| Fair Value, Recurring
Assets
Mortgage servicing rights	$ 682	$ 569

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