Summary of Significant Accounting Policies (Additional Cash Flow Information) (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accounting Policies [Abstract]
Interest	$ 697,731	$ 788,377	$ 616,274
U.S. federal income taxes, net of refunds received	110,500	121,986	117,986
State income/franchise taxes, net of refunds received	1,806	1,910	719
Unsettled securities transactions	20,716	501,587	1,452
Loans foreclosed and transferred to other real estate owned and foreclosed assets	659	19,297	0
Right-of-use lease assets obtained in exchange for lessee operating lease liabilities	$ 13,728	$ 15,044	$ 15,259

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Amount, after income tax refund received, of cash paid to federal (national) tax jurisdiction for tax on income.

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Amount, after income tax refund received, of cash paid to state and local tax jurisdictions for tax on income.

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The increase (decrease) during the reporting period in the aggregate amount of obligations incurred arising from transactions with broker-dealers, such as amounts due on margin and unsettled cash transactions; includes payables to brokers, dealers and clearing organizations.

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Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

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Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

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Value transferred from mortgage loans to real estate owned (REO) in noncash transactions.

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