Loans - Contractual Aging of Recorded Investment in Past Due Loans by Portfolio Classification of Loans (Detail) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	$ 2,578,472	$ 2,356,387
Recorded Investment > 90 Days and Accruing		0
30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,657	3,197
60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,735	674
Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,182	2,154
Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	11,574	6,025
Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,566,898	2,350,362
Consumer Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	521,908
Loans after net deferred loan fees and costs	521,908	494,423
Consumer Real Estate [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,914	1,536
Consumer Real Estate [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	137	635
Consumer Real Estate [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	670	90
Consumer Real Estate [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,721	2,261
Consumer Real Estate [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	519,187	492,162
Agricultural Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	223,479	220,514
Agricultural Real Estate [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	118
Agricultural Real Estate [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,429	2
Agricultural Real Estate [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	55	1,550
Agricultural Real Estate [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	3,484	1,670
Agricultural Real Estate [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	219,995	218,844
Agricultural [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	132,763
Loans after net deferred loan fees and costs	132,763	128,926
Agricultural [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	433
Agricultural [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,132	0
Agricultural [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	2,977	152
Agricultural [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	4,109	585
Agricultural [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	128,654	128,341
Commercial Real Estate [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,335,075
Loans after net deferred loan fees and costs	1,335,075	1,150,511
Commercial Real Estate [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	380	74
Commercial Real Estate [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Commercial Real Estate [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	255	180
Commercial Real Estate [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	635	254
Commercial Real Estate [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	1,334,440	1,150,257
Commercial and Industrial [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	284,894	272,119
Commercial and Industrial [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	145	953
Commercial and Industrial [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	0	0
Commercial and Industrial [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	199	182
Commercial and Industrial [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	344	1,135
Commercial and Industrial [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	284,550	270,984
Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans after net deferred loan fees and costs	80,353	89,894
Consumer [Member] | 30 to 59 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	218	83
Consumer [Member] | 60 to 89 Days Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	37	37
Consumer [Member] | Greater Than 90 Days [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	26
Consumer [Member] | Past Due [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	281	120
Consumer [Member] | Current [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total Past Due	$ 80,072	$ 89,774