Investments - Net Realized Investment Gains (Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Total impairment losses:	$ (3,298)	$ (3,111)	$ (1,772)
Portion of impairment losses recognized in other comprehensive income before taxes:	102	0	14
Net impairment losses recognized in earnings	(3,196)	(3,111)	(1,758)
Gross realized gains, available-for-sale fixed maturities	1,527	876	1,740
Gross realized (losses), available-for-sale fixed maturities	(4,116)	(1,860)	(3,387)
Net realized gains (losses), trading fixed maturities	34	(88)	(155)
Net realized gains (losses), equity investments	2,559	496	(5,252)
Net realized gains (losses), other investments	(826)	(2,417)	(222)
Change in unrealized holding gains (losses), trading fixed maturities	445	68	(613)
Change in unrealized holding gains (losses), equity investments	(2,313)	5,733	(22,166)
Change in unrealized holding gains (losses), convertible securities, carried at fair value	866	5,774	(10,557)
Other	6,923	8,357	9,213
Total net investment gains (losses)	1,903	13,828	(33,157)
NORCAL Group
Debt Securities, Available-for-sale [Line Items]
Gain on fair value of contingent consideration	6,500	5,000	9,000
Corporate Debt
Debt Securities, Available-for-sale [Line Items]
Total impairment losses:	(2,710)	(2,984)	(1,331)
Portion of impairment losses recognized in other comprehensive income before taxes:	102	0	0
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total impairment losses:	(588)	(127)	(441)
Portion of impairment losses recognized in other comprehensive income before taxes:	$ 0	$ 0	$ 14