Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 195,000	$ 274,000
Fixed maturity securities, fair value	575,850,000	621,654,000
Fixed maturity securities, available-for-sale, allowance for credit losses	0	0
Fixed maturity securities, amortized cost	324,597,000	387,665,000
Equity securities, cost	44,175,000	35,787,000
Amounts recoverable from reinsurers, allowance for credit losses	440,000	452,000
Premiums receivable, allowance for credit losses	$ 4,386,000	$ 4,791,000	$ 5,112,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	20,622,304	20,589,309
Common stock, shares outstanding	19,364,054	19,331,059
Treasury stock, shares	1,258,250	1,258,250