Revenue Recognition - Summary of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 2,601	$ 2,523	$ 5,149	$ 5,098
Digital banking income	5,040	5,010	9,745	9,615
Net swap fee and valuation income	1,776	2,612	3,339	3,411
Mortgage banking income	1,069	601	1,762	1,027
Net gain on other real estate owned and other assets	34	871	188	1,104
Total Service Charges on Deposits [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	7,111	6,232	13,895	12,401
Trust Account fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	5,305	5,009	$ 11,405	10,614
Point of revenue recognition			Over time
WesMark Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	1,998	1,909	$ 3,980	3,798
Point of revenue recognition			Over time
Total Trust Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	7,303	6,918	$ 15,385	14,412
Commercial Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	1,297	650	$ 2,485	1,259
Point of revenue recognition			Over time
Personal Service Charges [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	5,814	5,582	$ 11,410	11,142
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	1,978	1,840	$ 3,950	3,885
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	70	149	$ 150	149
Point of revenue recognition			At a point in time
Managed Money [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	272	284	$ 526	567
Point of revenue recognition			Over time
Trail Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	281	250	$ 523	497
Point of revenue recognition			Over time
Payment Processing Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Payment Processing Fees	$ 906	$ 951	$ 1,734	$ 1,822
Point of revenue recognition			At a point in time and over time
Digital Banking Income [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