Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Assets
Securities available for sale	$ 131,536	$ 87,358
Mortgage servicing rights	1,818	1,242
Financial derivatives	3,620	4,379
Liabilities
Financial derivatives	$ 985	$ 584
Assets at fair value \| Assets, Total \| Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	26.00%	22.00%
Level 3 assets \| Assets, Total \| Assets
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	4.00%	5.00%
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 \| Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	1.00%	1.00%
Level 3 liabilities \| Liabilities, Total \| Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	10.00%	9.00%
Level 3 liabilities \| Liabilities \| Liabilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Concentration risk, percentage	1.00%	1.00%
Fair Value, Measurements, Recurring
Assets
Securities available for sale	$ 131,536	$ 87,358
Loans	1,501	1,365
Equity investments	3,231	2,629
Trading securities	1,851	2,238
Financial derivatives	5,152	6,533
Other assets	518	454
Total Assets	147,484	103,035
Liabilities
Other borrowed funds	773	707
Financial derivatives	3,570	2,756
Other liabilities	175	43
Total liabilities	4,518	3,506
Residential Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	1,302	854
Mortgage servicing rights	1,078	673
Commercial Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	575	362
Mortgage servicing rights	740	569
U.S. Treasury and government agencies \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	46,164	20,711
Residential mortgage-backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	67,632	48,911
Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	1,158	1,501
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	1,773	2,688
Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	3,436	3,689
Asset-backed \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	6,409	5,150
Other \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	4,964	4,708
Level 1 \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	41,873	16,675
Equity investments	1,373	1,070
Trading securities	250	548
Financial derivatives	5
Other assets	404	373
Total Assets	43,905	18,666
Liabilities
Other borrowed funds	725	661
Total liabilities	725	661
Level 1 \| U.S. Treasury and government agencies \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	41,873	16,675
Level 2 \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	88,331	69,036
Loans	617	718
Trading securities	1,601	1,690
Financial derivatives	5,109	6,415
Other assets	114	81
Total Assets	97,519	78,936
Liabilities
Other borrowed funds	45	44
Financial derivatives	3,285	2,483
Total liabilities	3,330	2,527
Level 2 \| Residential Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	1,221	691
Level 2 \| Commercial Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	526	305
Level 2 \| U.S. Treasury and government agencies \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	4,291	4,036
Level 2 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	67,632	48,911
Level 2 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	61	136
Level 2 \| Commercial Mortgage Backed Securities \| Mortgage-backed Securities Agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	1,773	2,688
Level 2 \| Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	3,433	3,678
Level 2 \| Asset-backed \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	6,246	4,951
Level 2 \| Other \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	4,895	4,636
Level 3 \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	1,332	1,647
Loans	884	647
Equity investments	1,680	1,263
Financial derivatives	38	118
Total Assets	5,882	5,137
Liabilities
Other borrowed funds	3	2
Financial derivatives	285	273
Other liabilities	175	43
Total liabilities	463	318
Level 3 \| Residential Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	81	163
Mortgage servicing rights	1,078	673
Level 3 \| Commercial Mortgages \| Fair Value, Measurements, Recurring
Assets
Loans held for sale	49	57
Mortgage servicing rights	740	569
Level 3 \| Residential mortgage-backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	1,097	1,365
Level 3 \| Commercial Mortgage Backed Securities \| Mortgage-backed Securities Non-agency \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	3	11
Level 3 \| Asset-backed \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	163	199
Level 3 \| Other \| Fair Value, Measurements, Recurring
Assets
Securities available for sale	$ 69	$ 72

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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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Fair value of obligations measured on a recurring basis.

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Fair value of an asset representing net future revenue from contractually specified servicing fees, late charges, and other ancillary revenues, in excess of future costs related to servicing arrangements.

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Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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