Securities - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Equities securities	$ 18,303		$ 30,809
Other assets	647,905		543,212
Proceeds from sale of available-for-sale securities	22,337	$ 876,893
Net unrealized losses on available-for-sale securities included in AOCI	241,600		139,500
Accrued interest receivable	106,182		106,651
Federal home loan bank stock, Total	93,400		58,500
Asset Pledged as Security
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Other assets	2,700,000		2,800,000
Us Government Securities and Mortgage Backed and Collateralized Securities Issued By Direct Governmental Entity or Government-Sponsored Entity [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Estimated credit losses	0
Held-to-maturity Securities [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Accrued interest receivable	7,700		8,200
Grantor Trusts [Member]
Schedule Of Available For Sale Securities And Held To Maturity [Line Items]
Equities securities	$ 15,800		$ 28,200

Amount, after tax, of accumulated unrealized gain (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 of expense (reversal of expense) for expected credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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Amount of assets classified as other.

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