Schedule II - Condensed Financial Information of Registrant (Parent Company) - Condensed Statements of Cash Flows (Details) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash flows from operating activities:
Net earnings	$ 345,779,000	$ 304,611,000	$ 583,411,000
Adjustments to reconcile net losses to net cash provided by (used in) operating activities:
Net realized (gains) losses	(19,966,000)	(32,518,000)	(588,515,000)
Depreciation	7,664,000	8,545,000	7,981,000
Other items, net	13,725,000	24,947,000	(20,467,000)
Changes in investment in unconsolidated investees:
Undistributed earnings	4,869,000	(9,610,000)	(9,853,000)
Dividends received from investments in unconsolidated investees		0	0
Net cash provided by operating activities	560,219,000	464,257,000	250,448,000
Purchase of:
Fixed income securities, available-for-sale	(811,926,000)	(662,070,000)	(2,053,359,000)
Other	(10,956,000)	(10,786,000)	(5,704,000)
Sale of:
Fixed income securities - available-for-sale	149,939,000	50,135,000	53,300,000
Equity method investments		14,284,000	686,666,000
Property and equipment	13,000	27,000	375,000
Call or maturity of:
Fixed income securities - available-for-sale	326,297,000	504,168,000	1,393,674,000
Net sale (purchase) of short-term investments	60,008,000	(98,694,000)	(36,229,000)
Net cash provided by (used in) investing activities	(318,870,000)	(211,803,000)	48,879,000
Cash Flows from Financing Activities
Proceeds from stock option exercises	(2,327,000)	1,245,000	(465,000)
Proceeds from issuance of debt	73,000,000	100,000,000
Repayment of debt	(73,000,000)	(200,000,000)
Net cash used in financing activities	(237,983,000)	(238,848,000)	(365,313,000)
Net increase (decrease) in cash	3,366,000	13,606,000	(65,986,000)
Cash at the beginning of year	36,424,000	22,818,000	88,804,000
Cash at end of year	39,790,000	36,424,000	22,818,000
Parent Company
Cash flows from operating activities:
Net earnings	(7,248,000)	3,827,000	448,284,000
Adjustments to reconcile net losses to net cash provided by (used in) operating activities:
Net realized (gains) losses	1,542,000	(14,134,000)	(570,888,000)
Depreciation		35,000	64,000
Other items, net	6,553,000	1,350,000	1,403,000
Change in:
Affiliate balances receivable/payable	28,000	(821,000)	(724,000)
Federal income taxes	(1,364,000)	(1,409,000)	(19,484,000)
Changes in investment in unconsolidated investees:
Undistributed earnings			(372,000)
Net cash provided by operating activities	(489,000)	(11,152,000)	(141,717,000)
Purchase of:
Fixed income securities, available-for-sale		(89,501,000)	(1,356,177,000)
Other	(3,993,000)	(1,832,000)	(1,420,000)
Sale of:
Fixed income securities - available-for-sale	26,921,000		1,373,000
Equity method investments		14,134,000	686,566,000
Property and equipment			298,000
Other	1,024,000	54,000	221,000
Call or maturity of:
Fixed income securities - available-for-sale	1,968,000	263,939,000	1,192,050,000
Net sale (purchase) of short-term investments	75,526,000	(74,696,000)	(2,229,000)
Cash dividends received-subsidiaries	152,000,000	145,000,000	13,000,000
Net cash provided by (used in) investing activities	253,446,000	257,098,000	533,682,000
Cash Flows from Financing Activities
Proceeds from stock option exercises	(2,327,000)	1,245,000	(465,000)
Proceeds from issuance of debt		50,000,000
Repayment of debt		(150,000,000)
Cash dividends paid	(256,443,000)	(152,508,000)	(397,323,000)
Other	4,886,000	5,314,000	5,441,000
Net cash used in financing activities	(253,884,000)	(245,949,000)	(392,347,000)
Net increase (decrease) in cash	(927,000)	(3,000)	(382,000)
Cash at the beginning of year	1,048,000	1,051,000	1,433,000
Cash at end of year	$ 121,000	$ 1,048,000	$ 1,051,000