Schedule II - Condensed Financial Information of Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Cash	$ 36,424	$ 22,818
Short-term investments, at cost which approximates fair value	134,923	36,229
Investment in unconsolidated investees	56,966	58,275
Fixed income:
Available-for-sale, at fair value (amortized cost of $78,431 and allowance for credit losses of $0 in 2023) (amortized cost of $250,904 and allowance for credit losses of $0 in 2022)	2,855,849	2,666,950
Property and equipment, at cost, net of accumulated depreciation of $1,375 in 2023 and $1,340 in 2022	46,715	49,573
Income taxes-deferred	15,872	40,269
TOTAL ASSETS	5,180,221	4,767,068
Liabilities
Income taxes-current	3,757
Debt	100,000	199,863
TOTAL LIABILITIES	3,766,707	3,589,727
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 200,000,000) (68,570,261 shares issued and 45,640,047 shares outstanding in 2023) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022)	686	684
Paid-in capital	362,345	352,391
Accumulated other comprehensive earnings	(166,303)	(229,076)
Retained earnings	1,609,785	1,446,341
Deferred compensation	13,539	12,015
Treasury shares, at cost (22,930,214 shares in 2023 and 2022)	(406,538)	(405,014)
TOTAL SHAREHOLDERS' EQUITY	1,413,514	1,177,341	$ 1,229,361	$ 1,135,978
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	5,180,221	4,767,068
Parent Company
ASSETS
Cash	1,048	1,051
Short-term investments, at cost which approximates fair value	76,926	2,229
Accounts receivable, affiliates	2,393	1,572
Investments in subsidiaries	1,312,323	1,084,055
Fixed income:
Available-for-sale, at fair value (amortized cost of $78,431 and allowance for credit losses of $0 in 2023) (amortized cost of $250,904 and allowance for credit losses of $0 in 2022)	67,029	237,282
Property and equipment, at cost, net of accumulated depreciation of $1,375 in 2023 and $1,340 in 2022	1,375	1,410
Income taxes-deferred	3,101	3,204
Other assets	6,170	3,840
TOTAL ASSETS	1,470,365	1,334,643
Liabilities
Income taxes-current	778	1,823
Debt	50,000	149,863
Interest payable on debt	157	2,153
Other liabilities	5,916	3,463
TOTAL LIABILITIES	56,851	157,302
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 200,000,000) (68,570,261 shares issued and 45,640,047 shares outstanding in 2023) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022)	686	684
Paid-in capital	362,345	352,391
Accumulated other comprehensive earnings	(166,303)	(229,076)
Retained earnings	1,609,785	1,446,341
Deferred compensation	13,539	12,015
Treasury shares, at cost (22,930,214 shares in 2023 and 2022)	(406,538)	(405,014)
TOTAL SHAREHOLDERS' EQUITY	1,413,514	1,177,341
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 1,470,365	$ 1,334,643