Fair Value Accounting - Schedule of Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Financial assets
Investment securities held to maturity	$ 2,380	$ 2,591
Loans held for sale	686	97
Financial liabilities
FHLB advances and other borrowings	9,985	2,205
Level 1
Financial assets
Securities purchased with agreement to resell	0	0
Investment securities held to maturity	0	20
Loans held for sale	0	0
Loans, net	0	0
Financial liabilities
Deposits and securities sold under agreements to repurchase	0	0
FHLB advances and other borrowings	0	0
Level 2
Financial assets
Securities purchased with agreement to resell	0	0
Investment securities held to maturity	2,050	2,390
Loans held for sale	658	98
Loans, net	0	0
Financial liabilities
Deposits and securities sold under agreements to repurchase	0	0
FHLB advances and other borrowings	0	0
Level 3
Financial assets
Securities purchased with agreement to resell	26	96
Investment securities held to maturity	0	0
Loans held for sale	0	0
Loans, net	87,497	38,288
Financial liabilities
Deposits and securities sold under agreements to repurchase	103,605	46,735
FHLB advances and other borrowings	9,982	2,232
Carrying Value
Financial assets
Securities purchased with agreement to resell	26	96
Investment securities held to maturity	2,380	2,591
Loans held for sale	658	97
Loans, net	88,822	38,712
Financial liabilities
Deposits and securities sold under agreements to repurchase	103,622	47,717
FHLB advances and other borrowings	9,985	2,205
Fair Value
Financial assets
Securities purchased with agreement to resell	26	96
Investment securities held to maturity	2,050	2,410
Loans held for sale	658	98
Loans, net	87,497	38,288
Financial liabilities
Deposits and securities sold under agreements to repurchase	103,605	46,735
FHLB advances and other borrowings	$ 9,982	$ 2,232

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Federal Home Loan Bank (FHLB) Advances And Other Borrowings

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Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

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Amount, before valuation allowance, of financing receivable classified as held-for-sale.

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Amortized cost, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement and net investment in lease.

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