Loans and Allowance for Credit Losses - Modifications Subsequent Default (Detail) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026 USD ($) Contract	Dec. 31, 2025 USD ($) Contract
Financing Receivable, Modified, Subsequent Default [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 414	$ 2,843
Financing Receivable, Modified, Subsequent Default, Number of contracts \| Contract	3,000	3,000
Commercial, financial, agricultural and other [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 100	$ 2,522
Financing Receivable, Modified, Subsequent Default, Number of contracts \| Contract	1,000	1,000
Commercial, financial, agricultural and other [Member] \| Time and Demand Loans Other
Financing Receivable, Modified, Subsequent Default [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 100	$ 2,522
Financing Receivable, Modified, Subsequent Default, Number of contracts \| Contract	1,000	1,000
Residential real estate [Member]
Financing Receivable, Modified, Subsequent Default [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 314	$ 321
Financing Receivable, Modified, Subsequent Default, Number of contracts \| Contract	2,000	2,000
Residential real estate [Member] \| Senior Lien
Financing Receivable, Modified, Subsequent Default [Line Items]
Financing Receivable, Troubled Debt Restructuring, Subsequent Default \| $	$ 314	$ 321
Financing Receivable, Modified, Subsequent Default, Number of contracts \| Contract	2,000	2,000