Allowance for Credit Losses - Ending Allocation of Allowance for Loan Losses and Loan Balances Outstanding (Detail) - USD ($)	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	$ 35,280,000	$ 35,149,000	$ 28,511,000
Allowance for loan losses, Individually evaluated for impairment			7,000
Allowance for loan losses, Collectively evaluated for impairment			28,495,000
Allowance for loan losses, Total			28,511,000	$ 27,773,000	$ 27,435,000	$ 26,641,000
Outstanding loan balances, Individually evaluated for impairment			624,000
Outstanding loan balances, Collectively evaluated for impairment			2,541,657,000
Outstanding loan balances, Total	2,754,890,000		2,546,666,000
Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration			9,000
Loan balance of loans acquired with credit deterioration			4,385,000
Commercial and Agriculture [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	5,156,000	5,540,000	3,011,000
Allowance for loan losses, Collectively evaluated for impairment			3,005,000
Allowance for loan losses, Total			3,011,000	2,729,000	2,790,000	2,600,000
Outstanding loan balances, Collectively evaluated for impairment			277,732,000
Outstanding loan balances, Total	301,877,000		278,595,000
Commercial and Agriculture [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration			6,000
Loan balance of loans acquired with credit deterioration			863,000
Commercial Real Estate Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	5,481,000	5,531,000	4,565,000
Allowance for loan losses, Individually evaluated for impairment			6,000
Allowance for loan losses, Collectively evaluated for impairment			4,556,000
Allowance for loan losses, Total			4,565,000	4,926,000	4,729,000	4,464,000
Outstanding loan balances, Individually evaluated for impairment			232,000
Outstanding loan balances, Collectively evaluated for impairment			368,927,000
Outstanding loan balances, Total	375,851,000		371,147,000
Commercial Real Estate Owner Occupied [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration			3,000
Loan balance of loans acquired with credit deterioration			1,988,000
Commercial Real Estate Non Owner Occupied [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	11,555,000	11,646,000	14,138,000
Allowance for loan losses, Collectively evaluated for impairment			14,138,000
Allowance for loan losses, Total			14,138,000	14,427,000	14,711,000	13,860,000
Outstanding loan balances, Collectively evaluated for impairment			1,018,617,000
Outstanding loan balances, Total	1,102,932,000		1,018,736,000
Commercial Real Estate Non Owner Occupied [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration			119,000
Residential Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	6,831,000	6,515,000	3,145,000
Allowance for loan losses, Individually evaluated for impairment			1,000
Allowance for loan losses, Collectively evaluated for impairment			3,144,000
Allowance for loan losses, Total			3,145,000	3,036,000	2,859,000	2,597,000
Outstanding loan balances, Individually evaluated for impairment			392,000
Outstanding loan balances, Collectively evaluated for impairment			550,975,000
Outstanding loan balances, Total	614,304,000		552,781,000
Residential Real Estate [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration			1,414,000
Real Estate Construction [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	3,739,000	3,447,000	2,293,000
Allowance for loan losses, Collectively evaluated for impairment			2,293,000
Allowance for loan losses, Total			2,293,000	2,013,000	1,969,000	1,810,000
Outstanding loan balances, Collectively evaluated for impairment			243,127,000
Outstanding loan balances, Total	269,291,000		243,127,000
Farm Real Estate [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	227,000	243,000	291,000
Allowance for loan losses, Collectively evaluated for impairment			291,000
Allowance for loan losses, Total			291,000	251,000	236,000	287,000
Outstanding loan balances, Collectively evaluated for impairment			24,708,000
Outstanding loan balances, Total	24,109,000		24,708,000
Lease Financing Receivables [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	1,832,000	1,947,000	429,000
Allowance for loan losses, Collectively evaluated for impairment			429,000
Allowance for loan losses, Total			429,000
Outstanding loan balances, Collectively evaluated for impairment			36,797,000
Outstanding loan balances, Total	48,259,000		36,797,000
Consumer and Other [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	248,000	272,000	98,000
Allowance for loan losses, Collectively evaluated for impairment			98,000
Allowance for loan losses, Total			98,000	142,000	130,000	176,000
Outstanding loan balances, Collectively evaluated for impairment			20,774,000
Outstanding loan balances, Total	18,267,000		20,775,000
Consumer and Other [Member] | Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts Notes And Loans Receivable [Line Items]
Loan balance of loans acquired with credit deterioration			1,000
Unallocated [Member]
Accounts Notes And Loans Receivable [Line Items]
Loans acquired with credit deterioration	$ 211,000	$ 8,000	541,000
Allowance for loan losses, Collectively evaluated for impairment			541,000
Allowance for loan losses, Total			$ 541,000	$ 249,000	$ 11,000	$ 847,000