Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Fixed maturity securities, held-to-maturity, allowance for credit losses	$ 166	$ 274
Fixed maturity securities, fair value	603,720	621,654
Fixed maturity securities, available-for-sale, allowance for credit losses	0	0
Fixed maturity securities, amortized cost	391,687	387,665
Equity securities, cost	37,682	35,787
Amounts recoverable from reinsurers, allowance for credit losses	452	452
Premiums receivable, allowance for credit losses	$ 4,803	$ 4,791
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	20,589,309	20,589,309
Common stock, shares outstanding	19,331,059	19,331,059
Treasury stock, shares	1,258,250	1,258,250