Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	$ 1,278	$ 1,501
Aggregate unpaid principal balance of assets for which fair value option was elected	1,543	1,804
Fair value option aggregate difference assets	(265)	(303)
Other assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	101	105
Aggregate unpaid principal balance of assets for which fair value option was elected	114	107
Fair value option aggregate difference assets	(13)	(2)
Other borrowed funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	20	30
Aggregate unpaid principal balance, other borrowed funds	20	30
Difference, Other borrowed funds
Other liabilities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	175
Difference, Other borrowed funds	175
Accruing loans less than 90 days past due | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	472	487
Aggregate unpaid principal balance of assets for which fair value option was elected	484	498
Fair value option aggregate difference assets	(12)	(11)
Accruing loans 90 days or more past due | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	152	262
Aggregate unpaid principal balance of assets for which fair value option was elected	166	278
Fair value option aggregate difference assets	(14)	(16)
Nonaccrual loans | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	654	752
Aggregate unpaid principal balance of assets for which fair value option was elected	893	1,028
Fair value option aggregate difference assets	(239)	(276)
Residential mortgage loans held for sale | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	835	1,302
Aggregate unpaid principal balance of assets for which fair value option was elected	872	1,282
Fair value option aggregate difference assets	(37)	20
Residential mortgage loans held for sale | Accruing loans less than 90 days past due | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	769	1,249
Aggregate unpaid principal balance of assets for which fair value option was elected	794	1,219
Fair value option aggregate difference assets	(25)	30
Residential mortgage loans held for sale | Accruing loans 90 days or more past due | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	8	6
Aggregate unpaid principal balance of assets for which fair value option was elected	8	6
Residential mortgage loans held for sale | Nonaccrual loans | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	58	47
Aggregate unpaid principal balance of assets for which fair value option was elected	70	57
Fair value option aggregate difference assets	(12)	(10)
Commercial mortgage loans held for sale | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	235	575
Aggregate unpaid principal balance of assets for which fair value option was elected	267	580
Fair value option aggregate difference assets	(32)	(5)
Commercial mortgage loans held for sale | Accruing loans less than 90 days past due | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	218	575
Aggregate unpaid principal balance of assets for which fair value option was elected	222	580
Fair value option aggregate difference assets	(4)	(5)
Commercial mortgage loans held for sale | Nonaccrual loans | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	17
Aggregate unpaid principal balance of assets for which fair value option was elected	45
Fair value option aggregate difference assets	$ (28)