Schedule II - Condensed Financial Information of Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
ASSETS
Cash	$ 22,818	$ 88,804
Short-term investments, at cost which approximates fair value	36,229
Investment in unconsolidated investees	58,275	171,311
Fixed income:
Available-for-sale, at fair value (amortized cost of $250,904 and allowance for credit losses of $0 in 2022) (amortized cost of $84,823 and allowance for credit losses of $0 in 2021)	2,666,950	2,409,887
Property and equipment, at cost, net of accumulated depreciation of $1,340 in 2022 and $1,697 in 2021	49,573	52,161
Income taxes-deferred	40,269
TOTAL ASSETS	4,767,068	4,508,302
Liabilities
Current portion of long-term debt	199,863
Long-term debt		199,676
TOTAL LIABILITIES	3,589,727	3,278,941
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 200,000,000) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022)	684	682
Paid-in capital	352,391	343,742
Accumulated other comprehensive earnings (loss)	(229,076)	49,826
Retained earnings	1,446,341	1,228,110
Deferred compensation	12,015	9,642
Treasury shares, at cost (22,930,214 shares in 2022 and 2021)	(405,014)	(402,641)
TOTAL SHAREHOLDERS' EQUITY	1,177,341	1,229,361	$ 1,135,978	$ 995,388
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	4,767,068	4,508,302
Parent Company
ASSETS
Cash	1,051	1,433
Short-term investments, at cost which approximates fair value	2,229
Accounts receivable, affiliates	1,572	848
Investments in subsidiaries	1,084,055	1,197,997
Investment in unconsolidated investees		113,052
Fixed income:
Available-for-sale, at fair value (amortized cost of $250,904 and allowance for credit losses of $0 in 2022) (amortized cost of $84,823 and allowance for credit losses of $0 in 2021)	237,282	86,483
Property and equipment, at cost, net of accumulated depreciation of $1,340 in 2022 and $1,697 in 2021	1,410	1,711
Income taxes receivable - current		211
Income taxes-deferred	3,204
Other assets	3,840	2,907
TOTAL ASSETS	1,334,643	1,404,642
Liabilities
Income taxes-current	1,823
Income taxes - deferred		21,067
Current portion of long-term debt	149,863
Long-term debt		149,676
Interest payable, long-term debt	2,153	2,153
Other liabilities	3,463	2,385
TOTAL LIABILITIES	157,302	175,281
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 200,000,000) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022) (68,399,966 shares issued and 45,469,752 shares outstanding in 2022)	684	682
Paid-in capital	352,391	343,742
Accumulated other comprehensive earnings (loss)	(229,076)	49,826
Retained earnings	1,446,341	1,228,110
Deferred compensation	12,015	9,642
Treasury shares, at cost (22,930,214 shares in 2022 and 2021)	(405,014)	(402,641)
TOTAL SHAREHOLDERS' EQUITY	1,177,341	1,229,361
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 1,334,643	$ 1,404,642