Investment Securities - Schedule of Investment Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Taxable interest	$ 230	$ 243	$ 668	$ 732
Taxable dividends	5	5	15	15
Interest and dividends exempt from U.S. federal income tax	6	5	18	16
Interest and dividends on investment securities	$ 241	$ 253	$ 701	$ 763

Amount of operating dividend income on securities subject to state, federal and other income tax.

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Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on securities.

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Interest income, including any amortization and accretion (as applicable) of discounts and premiums, derived from debt securities issued by municipal governments, local taxing districts and US state government agencies.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

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