Securities - Schedule of Gross Gains and Gross Losses on Sales of Securities Available for Sale (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Debt Securities, Available-for-sale [Line Items]
Gross realized gains on sales	$ 50	$ 0	$ 79	$ 0
Gross realized losses on sales	(51)	0	(106)	(13)
Investment securities gains (losses), net	(1)	$ 0	(27)	$ (13)
U.S Treasury Securities and State and Municipal Securities
Debt Securities, Available-for-sale [Line Items]
Gross realized gains on sales	$ 50		$ 74

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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