Fair Value (Reconciliation of Recurring Fair Value Measurements) (Details) - Fair Value, Recurring - Level 3 - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 5,882	$ 5,137
Included in Earnings	412	497
Included in other comprehensive income	(28)	19
Purchases	165	249
Sales	(20)	(46)
Issuances	42	31
Settlements	(237)	(271)
Transfers into Level 3	5	3
Transfers out of Level 3	(8)	(8)
Ending Balance	6,213	5,611
Unrealized gains/losses on assets held on Consolidated Balance Sheet	421	487
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	463	318
Included in Earnings	12	21
Sales	3	2
Issuances	73	31
Settlements	(156)	(70)
Ending Balance	395	302
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	14	(26)
Fair Value Additional Information [Abstract]
Net gains (losses) included in earnings (realized and unrealized) relating to Level 3 assets and liabilities	400	476
Net unrealized gains (losses) relating to Level 3 assets and liabilities	407	513
Loans held for sale \| Residential mortgage loans held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	81	163
Included in Earnings	(1)	1
Purchases	37	35
Sales	(2)	(16)
Settlements	(5)	(16)
Transfers into Level 3	5	3
Transfers out of Level 3	(7)	(5)
Ending Balance	108	165
Unrealized gains/losses on assets held on Consolidated Balance Sheet	(1)
Loans held for sale \| Commercial mortgage loans held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	49	57
Included in Earnings	(4)	(1)
Ending Balance	45	56
Unrealized gains/losses on assets held on Consolidated Balance Sheet	(3)
Securities available for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,332	1,647
Included in Earnings	8	10
Included in other comprehensive income	(28)	19
Purchases	1	1
Sales
Settlements	(73)	(84)
Ending Balance	1,240	1,593
Securities available for sale \| Residential mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,097	1,365
Included in Earnings	8	9
Included in other comprehensive income	(23)	16
Settlements	(63)	(74)
Ending Balance	1,019	1,316
Securities available for sale \| Commercial mortgage-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3	11
Ending Balance	3	11
Securities available for sale \| Asset-backed
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	163	199
Included in Earnings		1
Included in other comprehensive income	(4)	3
Settlements	(7)	(9)
Ending Balance	152	194
Securities available for sale \| Other
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	69	72
Included in other comprehensive income	(1)
Purchases	1	1
Settlements	(3)	(1)
Ending Balance	66	72
Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	884	647
Included in Earnings	11	10
Purchases	13	88
Sales	(7)	(3)
Settlements	(49)	(28)
Transfers out of Level 3	(1)	(3)
Ending Balance	851	711
Unrealized gains/losses on assets held on Consolidated Balance Sheet	11	11
Equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,680	1,263
Included in Earnings	53	67
Purchases	29	40
Sales	(11)	(27)
Ending Balance	1,751	1,343
Unrealized gains/losses on assets held on Consolidated Balance Sheet	53	63
Mortgage Servicing Rights \| Residential mortgage loans held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,078	673
Included in Earnings	207	295
Purchases	76	71
Issuances	21	13
Settlements	(60)	(73)
Ending Balance	1,322	979
Unrealized gains/losses on assets held on Consolidated Balance Sheet	208	295
Mortgage Servicing Rights \| Commercial mortgage loans held for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	740	569
Included in Earnings	151	129
Purchases	8	13
Issuances	21	18
Settlements	(34)	(28)
Ending Balance	886	701
Unrealized gains/losses on assets held on Consolidated Balance Sheet	151	129
Financial derivatives
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	38	118
Included in Earnings	(13)	(14)
Purchases	1	1
Settlements	(16)	(42)
Ending Balance	10	63
Unrealized gains/losses on assets held on Consolidated Balance Sheet	2	(11)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	285	273
Included in Earnings	5	(14)
Sales	3	2
Settlements	(59)	(34)
Ending Balance	234	227
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	8	(30)
Other borrowed funds
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3	2
Issuances	2	1
Settlements	(2)	(1)
Ending Balance	3	2
Other liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	175	43
Included in Earnings	7	35
Issuances	71	30
Settlements	(95)	(35)
Ending Balance	158	73
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	$ 6	$ 4

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This element represents net gains or losses for the period (realized and unrealized), arising from assets and liabilities measure at fair value on a recurring basis using unobservable inputs (Level 3), which are included in earnings or resulted in a change in net asset value.

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of unrealized gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of gain (loss) recognized in other comprehensive income (OCI) from asset measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of issuances of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Fair value of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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