Other Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Schedule Of Other Assets [Line Items]
Other assets	$ 345,292	$ 323,573
Federal Home Loan Bank ("FHLB") and Federal Reserve Bank ("Federal Reserve")
Schedule Of Other Assets [Line Items]
Fair value of equity securities	135,200	134,600
First National Bankers' Bank and Other Miscellaneous Holdings
Schedule Of Other Assets [Line Items]
Fair value of equity securities	$ 91,200	$ 88,600

Amount of assets classified as other.

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Name:	us-gaap_OtherAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant