Revenue Recognition - Summary of Revenue Recognition (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 10,055	$ 9,525	$ 6,896
Debit card sponsorship income	0	0	646
Electronic banking fees	19,454	20,002	19,318
Net swap fee and valuation income	6,912	7,067	6,481
Mortgage banking income	2,652	5,129	19,528
Net gains on other real estate owned and other assets	1,520	482	4,816
Total Service Charges on Deposits [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	26,116	26,281	22,412
Trust Account fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 20,474	19,134	19,717
Point of revenue recognition	Over time
WesMark Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 7,661	8,417	9,794
Point of revenue recognition	Over time
Net Swap Fee and Valuation Income
Schedule Of Revenue Recognition [Line Items]
Point of revenue recognition	At a point in time
Total Trust Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 28,135	27,551	29,511
Commercial Banking Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 2,848	2,372	2,088
Point of revenue recognition	Over time
Personal Service Charges [Member]
Schedule Of Revenue Recognition [Line Items]
Total trust fees/Total service charges on deposits	$ 23,268	23,909	20,324
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	$ 7,677	7,258	4,331
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	$ 283	87	242
Point of revenue recognition	At a point in time
Managed Money [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 1,091	1,215	1,201
Point of revenue recognition	Over time
Trail Commissions [Member]
Schedule Of Revenue Recognition [Line Items]
Total net securities brokerage revenue	$ 1,004	965	1,122
Point of revenue recognition	Over time
Payment Processing Fees [Member]
Schedule Of Revenue Recognition [Line Items]
Payment Processing Fees	$ 3,652	$ 3,352	$ 3,100
Point of revenue recognition	At a point in time and over time
Debit Card Sponsorship Income [Member]
Schedule Of Revenue Recognition [Line Items]
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
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