Revenue Recognition - Summary of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 2,394	$ 2,491	$ 7,492	$ 6,969
Electronic banking fees	4,949	4,808	14,564	15,307
Net swap fee and valuation income	3,845	2,430	7,257	6,053
Mortgage banking income	975	1,257	2,002	4,508
Net (loss) gain on other real estate owned and other assets	(28)	2,040	1,075	(68)
Total Service Charges on Deposits [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	6,726	6,942	19,128	19,520
Trust Account fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	4,751	4,456	$ 15,365	14,413
Point of revenue recognition			Over time
WesMark Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	1,954	2,061	$ 5,751	6,466
Point of revenue recognition			Over time
Total Trust Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	6,705	6,517	$ 21,116	20,879
Commercial Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	756	606	$ 2,015	1,776
Point of revenue recognition			Over time
Personal Service Charges [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	5,970	6,336	$ 17,113	17,744
Point of revenue recognition			At a point in time and over time
Annuity Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	1,804	1,932	$ 5,689	5,193
Point of revenue recognition			At a point in time
Equity And Debt Security Trades [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	54	29	$ 203	94
Point of revenue recognition			At a point in time
Managed Money [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	275	290	$ 842	944
Point of revenue recognition			Over time
Trail Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	261	240	$ 758	738
Point of revenue recognition			Over time
Payment Processing Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Payment Processing Fees	$ 939	$ 818	$ 2,761	$ 2,436
Point of revenue recognition			At a point in time and over time
Electronic Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Point of revenue recognition			At a point in time
Net Swap Fee and Valuation Income [Member]
Schedule Of Revenue Recognition [Line Items]
Point of revenue recognition			At a point in time
Mortgage [Member]
Schedule Of Revenue Recognition [Line Items]
Point of revenue recognition			At a point in time
Other Real Estate Owned and Other Assets [Member]
Schedule Of Revenue Recognition [Line Items]
Point of revenue recognition			At a point in time and over time