Schedule II - Condensed Financial Information of Registrant (Parent Company) - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
ASSETS
Cash	$ 39,790	$ 36,424
Short-term investments, at cost which approximates fair value	74,915	134,923
Investment in unconsolidated investees	56,477	56,966
Fixed income:
Available-for-sale, at fair value (amortized cost of $47,655 and allowance for credit losses of $0 in 2024) (amortized cost of $78,431 and allowance for credit losses of $0 in 2023)	3,175,796	2,855,849
Property and equipment, at cost, net of accumulated depreciation of $913 in 2024 and $1,375 in 2023	43,172	46,715
Income taxes-deferred	7,793	15,872
TOTAL ASSETS	5,628,802	5,180,221
Liabilities
Income taxes-current	749	3,757
Short-term debt	100,000	100,000
TOTAL LIABILITIES	4,106,835	3,766,707
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 400,000,000) (137,598,560 shares issued and 91,738,132 shares outstanding in 2024) (137,140,522 shares issued and 91,280,094 shares outstanding in 2023)	1,376	1,371
Paid-in capital	367,645	361,660
Accumulated other comprehensive earnings	(173,723)	(166,303)
Retained earnings	1,719,668	1,609,785
Deferred compensation	13,498	13,539
Treasury stock, at cost (45,860,428 shares in 2024 and 2023)	(406,497)	(406,538)
TOTAL SHAREHOLDERS' EQUITY	1,521,967	1,413,514	$ 1,177,341	$ 1,229,361
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	5,628,802	5,180,221
Parent Company
ASSETS
Cash	121	1,048
Short-term investments, at cost which approximates fair value	1,400	76,926
Accounts receivable, affiliates	2,365	2,393
Investments in subsidiaries	1,525,833	1,312,323
Fixed income:
Available-for-sale, at fair value (amortized cost of $47,655 and allowance for credit losses of $0 in 2024) (amortized cost of $78,431 and allowance for credit losses of $0 in 2023)	37,372	67,029
Property and equipment, at cost, net of accumulated depreciation of $913 in 2024 and $1,375 in 2023	1,375	1,375
Income taxes receivable - current	349
Income taxes-deferred	3,104	3,101
Other assets	9,824	6,170
TOTAL ASSETS	1,581,743	1,470,365
Liabilities
Income taxes-current		778
Short-term debt	50,000	50,000
Interest payable on debt	108	157
Other liabilities	9,668	5,916
TOTAL LIABILITIES	59,776	56,851
Shareholders' Equity
Common stock ($0.01 par value) (Shares authorized - 400,000,000) (137,598,560 shares issued and 91,738,132 shares outstanding in 2024) (137,140,522 shares issued and 91,280,094 shares outstanding in 2023)	1,376	1,371
Paid-in capital	367,645	361,660
Accumulated other comprehensive earnings	(173,723)	(166,303)
Retained earnings	1,719,668	1,609,785
Deferred compensation	13,498	13,539
Treasury stock, at cost (45,860,428 shares in 2024 and 2023)	(406,497)	(406,538)
TOTAL SHAREHOLDERS' EQUITY	1,521,967	1,413,514
TOTAL LIABILITIES AND SHAREHOLDERS' EQUITY	$ 1,581,743	$ 1,470,365