Investments (Net Realized Investment Gains (Losses)) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	$ (1,801)	$ (141)	$ (3,302)	$ (3,117)
Corporate debt	0	0	102	0
Net impairment losses recognized in earnings	(1,801)	(141)	(3,200)	(3,117)
Gross realized gains, available-for-sale fixed maturities	484	254	1,156	793
Gross realized (losses), available-for-sale fixed maturities	(1,567)	(285)	(3,636)	(1,509)
Net realized gains (losses), trading fixed maturities	5	5	18	(101)
Net realized gains (losses), equity investments	176	154	2,115	254
Net realized gains (losses), other investments	(245)	(683)	(826)	(2,570)
Change in unrealized holding gains (losses), trading fixed maturities	(5)	(71)	165	81
Change in unrealized holding gains (losses), equity investments	4,979	(4,578)	1,762	(1,962)
Change in unrealized holding gains (losses), convertible securities, carried at fair value	267	(588)	873	3,473
Other	(41)	3,231	6,719	7,814
Total net investment gains (losses)	2,252	(2,702)	5,146	3,156
NORCAL Group
Debt Securities, Available-for-Sale [Line Items]
Gain on fair value of contingent consideration		1,500	6,500	4,500
Corporate Debt
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	(1,398)	0	(2,710)	(2,984)
Asset-backed securities
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	$ (403)	$ (141)	$ (592)	$ (133)

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