Federal Income Tax - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax liabilities
Deferred policy acquisition costs	$ 19,204	$ 18,289
Investments in partnerships	3,229	964
Prepaid pension cost	3,725	4,553
Over funded pension benefit	1,214	0
Net bond discount accretion	323	383
Depreciation	4,097	4,187
Revaluation of investment basis	0	325
Identifiable intangible assets	1,242	1,391
Capitalized Software	6,351	4,891
Other	2,183	1,568
Gross deferred tax liability	81,844	91,729
Deferred tax assets
Financial statement reserves in excess of income tax reserves	22,879	23,851
Unearned premium adjustment	17,296	18,979
Employee profit sharing	2,515	974
Underfunded benefit plan obligation	0	4,295
Post-retirement benefits other than pensions	2,650	9,533
Other-than-temporary impairment of investments	1,529	1,974
Compensation expense related to stock options	1,989	2,307
Nonqualified deferred compensation	2,574	2,066
Other	3,659	2,821
Deferred tax asset	55,091	66,800
Net deferred tax liability	26,753	24,929
Equity securities
Deferred tax liabilities
Net unrealized appreciation on investment securities	27,047	33,096
All other securities
Deferred tax liabilities
Net unrealized appreciation on investment securities	$ 13,229	$ 22,082