Investment Securities - Narrative (Details) - USD ($)	9 Months Ended	12 Months Ended
Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Held to maturity securities, assets pledged	$ 136,693,000,000	$ 146,453,000,000
Available for sale securities, assets pledged	62,308,000,000	82,994,000,000
Credit loss expense	0	0
Writedown to fair value	0	0
Available for sale, allowance for credit loss	0	0
Held to maturity securities, allowance for credit loss	0	0
Accrued interest receivable	372,000,000	455,000,000
Write-off of accrued interest receivable on available for sale and held to maturity securities	0	0
Asset Pledged as Collateral
Debt Securities, Available-for-sale [Line Items]
Held to maturity securities, assets pledged	2,047,000,000	5,920,000,000
Available for sale securities, assets pledged	311,000,000	378,000,000
Asset Pledged as Collateral \| Interest rate swaps
Debt Securities, Available-for-sale [Line Items]
Available for sale securities, assets pledged	311,000,000	378,000,000
Federal Home Loan Bank Advances
Debt Securities, Available-for-sale [Line Items]
Fair value of pledged securities	60,700,000,000
Collateral value of pledged securities	56,300,000,000
Federal Reserve Bank Advances
Debt Securities, Available-for-sale [Line Items]
Fair value of pledged securities	30,800,000,000
Collateral value of pledged securities	29,700,000,000
Deposits
Debt Securities, Available-for-sale [Line Items]
Fair value of pledged securities	1,700,000,000
Collateral value of pledged securities	1,700,000,000
U.S. agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Held to maturity securities, assets pledged	136,693,000,000	146,453,000,000
Available for sale securities, assets pledged	44,456,000,000	$ 51,833,000,000
U.S. agency mortgage-backed securities \| Asset Pledged as Collateral \| Securities Sold under Agreements to Repurchase
Debt Securities, Available-for-sale [Line Items]
Held to maturity securities, assets pledged	4,100,000,000
Held to maturity securities, assets pledged that may be sold, repledged, or utilized	$ 2,000,000,000.0

Debt Securities, Available-For-Sale And Held-To-Maturity, Accrued Interest, After Allowance For Credit Loss

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Debt Securities, Available-For-Sale And Held-To-Maturity, Accrued Interest Writeoff

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Debt Securities, Available-for-Sale, Excluding Accrued Interest, Write-down To Fair Value

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Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss, Amount Eligible For Sale And Utilization

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Securities Held as Collateral, at Collateral Value

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Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, excluding accrued interest, of decrease in allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) from writeoff.

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

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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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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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The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.

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