Fair Value (Fair Value Option - Fair Value and Principal Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	$ 1,117	$ 1,156
Aggregate unpaid principal balance of assets for which fair value option was elected	1,307	1,360
Fair value option aggregate difference assets	(190)	(204)
Other assets
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	193	133
Aggregate unpaid principal balance of assets for which fair value option was elected	189	142
Fair value option aggregate difference assets	4	(9)
Other borrowed funds
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	30	34
Aggregate unpaid principal balance, other borrowed funds	31	35
Difference, Other borrowed funds	(1)	(1)
Fair Value Of Liabilities For Which Fair Value Option Was Elected	30	34
Other Liabilities With Contractual Unpaid Principal Balance
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	28	28
Aggregate unpaid principal balance, other borrowed funds	31	32
Difference, Other borrowed funds	(3)	(4)
Fair Value Of Liabilities For Which Fair Value Option Was Elected	28	28
Other Liabilities Without Contractual Unpaid Principal Balance
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	121	106
Aggregate unpaid principal balance, other borrowed funds	0	0
Difference, Other borrowed funds	121	106
Fair Value Of Liabilities For Which Fair Value Option Was Elected	121	106
Interest-bearing deposits
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value of liabilities for which fair value option was elected	7,318	0
Aggregate unpaid principal balance, other borrowed funds	7,316	0
Difference, Other borrowed funds	2	0
Fair Value Of Liabilities For Which Fair Value Option Was Elected	7,318	0
Accruing loans less than 90 days past due \| Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	741	494
Aggregate unpaid principal balance of assets for which fair value option was elected	823	505
Fair value option aggregate difference assets	(82)	(11)
Accruing loans 90 days or more past due \| Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	123	126
Aggregate unpaid principal balance of assets for which fair value option was elected	136	137
Fair value option aggregate difference assets	(13)	(11)
Nonaccrual loans \| Loans
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	253	536
Aggregate unpaid principal balance of assets for which fair value option was elected	348	718
Fair value option aggregate difference assets	(95)	(182)
Residential mortgage loans held for sale \| Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	692	628
Aggregate unpaid principal balance of assets for which fair value option was elected	688	635
Fair value option aggregate difference assets	4	(7)
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	668	588
Aggregate unpaid principal balance of assets for which fair value option was elected	663	588
Fair value option aggregate difference assets	5	0
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	11	11
Aggregate unpaid principal balance of assets for which fair value option was elected	11	11
Fair value option aggregate difference assets	0	0
Residential mortgage loans held for sale \| Nonaccrual loans \| Loans held for sale
Fair Value, Option, Quantitative Disclosures [Line Items]
Fair value - assets	13	29
Aggregate unpaid principal balance of assets for which fair value option was elected	14	36
Fair value option aggregate difference assets	(1)	(7)
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	255	203
Aggregate unpaid principal balance of assets for which fair value option was elected	253	200
Fair value option aggregate difference assets	$ 2	$ 3

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- Definition

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+ References

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- Definition

Represents the fair value of assets for which the fair value option was elected.

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For assets for which the fair value option has been elected, this item represents the difference between the fair value and the aggregate unpaid principal balance for those assets.

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- Definition

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