Revenue Recognition - Summary of Revenue Recognition (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 2,548	$ 2,576
Digital banking income	4,704	4,605
Net swap fee and valuation income	1,563	799
Mortgage banking income	693	426
Net gain on other real estate owned and other assets	154	232
Total Service Charges on Deposits [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	6,784	6,170
Trust Account fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 6,099	5,605
Point of revenue recognition	Over time
WesMark Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 1,983	1,889
Point of revenue recognition	Over time
Total Trust Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 8,082	7,494
Commercial Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 1,188	609
Point of revenue recognition	Over time
Personal Service Charges [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 5,596	5,561
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	$ 1,972	2,046
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	$ 80
Point of revenue recognition	At a point in time
Managed Money [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 254	283
Point of revenue recognition	Over time
Trail Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 242	247
Point of revenue recognition	Over time
Payment Processing Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Payment Processing Fees	$ 829	$ 871
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