Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Allowance for credit losses on loans	$ 14,087,000	$ 14,171,000
Lease accounting	9,304,000	9,703,000
Defined postretirement benefit obligation	7,778,000	7,585,000
Accrued expenses	3,150,000	3,440,000
Securities available-for-sale	2,897,000	4,690,000
State income taxes	1,874,000	1,924,000
Stock compensation	1,501,000	1,363,000
Federal net operating loss carryforwards	1,403,000	1,719,000
Premises and equipment	1,375,000	1,677,000
California net operating loss carryforwards	986,000	1,106,000
Nonaccrual interest	135,000	174,000
Split-dollar life insurance benefit plan	71,000	49,000
Other	323,000	201,000
Total deferred tax assets	44,884,000	47,802,000
Deferred tax liabilities:
Lease accounting	(9,304,000)	(9,703,000)
Loan fees	(2,315,000)	(2,304,000)
Intangible liabilities	(1,639,000)	(1,940,000)
Prepaid expenses	(1,473,000)	(1,304,000)
FHLB stock	(156,000)	(156,000)
I/O strips	(30,000)	(40,000)
Other	(202,000)	(179,000)
Total deferred tax liabilities	(15,119,000)	(15,626,000)
Net deferred tax assets	$ 29,765,000	$ 32,176,000