Revenue Recognition - Summary of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 2,701	$ 2,548
Digital banking income	5,404	4,704
Net swap fee and valuation income	961	1,563
Mortgage banking income	1,140	693
Net gain on other real estate owned and other assets	(40)	154
Total Service Charges on Deposits [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	8,587	6,784
Trust Account fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 6,673	6,099
Point of revenue recognition	Over time
WesMark Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 2,024	1,983
Point of revenue recognition	Over time
Total Trust Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 8,697	8,082
Commercial Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 1,937	1,188
Point of revenue recognition	Over time
Personal Service Charges [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 6,650	5,596
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	$ 1,987	1,972
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	$ 124	80
Point of revenue recognition	At a point in time
Managed Money [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 327	254
Point of revenue recognition	Over time
Trail Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 262	242
Point of revenue recognition	Over time
Payment Processing Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Payment processing fees	$ 891	$ 829
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 (Loss) 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