Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	$ 1,287	$ 1,310
Aggregate unpaid principal balance of assets for which fair value option was elected	1,540	1,568
Fair value option aggregate difference assets	(253)	(258)
Other assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	65	80
Aggregate unpaid principal balance of assets for which fair value option was elected	71	80
Fair value option aggregate difference assets	(6)
Other borrowed funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	33	31
Aggregate unpaid principal balance, other borrowed funds	33	32
Difference, Other borrowed funds		(1)
Other liabilities
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	127	196
Difference, Other borrowed funds	127	196
Accruing loans less than 90 days past due | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	513	509
Aggregate unpaid principal balance of assets for which fair value option was elected	526	521
Fair value option aggregate difference assets	(13)	(12)
Accruing loans 90 days or more past due | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	141	155
Aggregate unpaid principal balance of assets for which fair value option was elected	151	167
Fair value option aggregate difference assets	(10)	(12)
Nonaccrual loans | Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	633	646
Aggregate unpaid principal balance of assets for which fair value option was elected	863	880
Fair value option aggregate difference assets	(230)	(234)
Residential mortgage loans held for sale | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	627	654
Aggregate unpaid principal balance of assets for which fair value option was elected	656	687
Fair value option aggregate difference assets	(29)	(33)
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	586	609
Aggregate unpaid principal balance of assets for which fair value option was elected	607	633
Fair value option aggregate difference assets	(21)	(24)
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	4	5
Aggregate unpaid principal balance of assets for which fair value option was elected	4	5
Residential mortgage loans held for sale | Nonaccrual loans | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	37	40
Aggregate unpaid principal balance of assets for which fair value option was elected	45	49
Fair value option aggregate difference assets	(8)	(9)
Commercial mortgage loans held for sale | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	317	276
Aggregate unpaid principal balance of assets for which fair value option was elected	351	300
Fair value option aggregate difference assets	(34)	(24)
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	302	261
Aggregate unpaid principal balance of assets for which fair value option was elected	307	256
Fair value option aggregate difference assets	(5)	5
Commercial mortgage loans held for sale | Nonaccrual loans | Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	15	15
Aggregate unpaid principal balance of assets for which fair value option was elected	44	44
Fair value option aggregate difference assets	$ (29)	$ (29)