Allowance for Loan Losses - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) SecurityLoan	Dec. 31, 2021 USD ($) SecurityLoan	Dec. 31, 2020 USD ($)	Jan. 01, 2023 USD ($)
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses		$ 37,160,000	$ 28,511,000
Allowance for credit losses		37,160,000	28,511,000
Provision for loan losses		$ 4,435,000	1,752,000	$ 830,000	$ 10,112,000
Number of days reaching where loans are considered for nonaccrual status		90 days
Conditions where loans are considered for nonaccrual status		A loan may be returned to accruing status only if one of three conditions are met: the loan is well-secured and none of the principal and interest has been past due for a minimum of 90 days; the loan is a TDR and the borrower has made a minimum of six months payments; or the principal and interest payments are reasonably assured and a sustained period of performance has occurred, generally six months.
Gross interest income recorded on nonaccrual loans		$ 446,000	384,000	307,000
Interest income on nonaccrual loans recognized on cash basis		343,000	$ 451,000	$ 716,000
Defaulted loans | SecurityLoan			0	0
Foreclosed assets		0	$ 0
Residential mortgages in process of foreclosure		1,018,000	399,000
Allowance for loan losses recorded for acquired loans		$ 0	0
Individually evaluated loans		greater than $350
Loans modified as troubled debt restructuring		$ 0
ASU 2016-13 [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses						$ 37,861,000
Allowance for credit losses			897,000
CECL Loans [Member] | ASU 2016-13 [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses						$ 7,682,000
Allowance for credit losses			4,296,000
Adjustment [Member] | ASU 2016-13 [Member]
Accounts Notes And Loans Receivable [Line Items]
Increase allowance of credit loss	$ 897,000
Adjustment [Member] | CECL Loans [Member] | ASU 2016-13 [Member]
Accounts Notes And Loans Receivable [Line Items]
Increase allowance of credit loss	$ 4,296,000
Civista Leasing And Finance [Member]
Accounts Notes And Loans Receivable [Line Items]
Provision for loan losses		$ 452,000
TDRs [Member]
Accounts Notes And Loans Receivable [Line Items]
Allowance for loan losses			$ 7,000	$ 18,000