Investments (Net Realized Investment Gains (Losses)) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	$ (9,000)	$ 43,000	$ 1,501,000	$ 2,976,000
Corporate debt	(474,000)	0	102,000	0
Net impairment losses recognized in earnings	(465,000)	(43,000)	(1,399,000)	(2,976,000)
Gross realized gains, available-for-sale fixed maturities	306,000	460,000	672,000	539,000
Gross realized (losses), available-for-sale fixed maturities	(970,000)	(767,000)	(2,069,000)	(1,224,000)
Net realized gains (losses), trading fixed maturities	(2,000)	2,000	13,000	(106,000)
Net realized gains (losses), equity investments	2,195,000	17,000	1,939,000	101,000
Net realized gains (losses), other investments	(2,357,000)	(2,115,000)	(581,000)	(1,886,000)
Change in unrealized holding gains (losses), trading fixed maturities	(44,000)	54,000	170,000	151,000
Change in unrealized holding gains (losses), equity investments	(3,991,000)	(1,130,000)	(3,217,000)	2,616,000
Change in unrealized holding gains (losses), convertible securities, carried at fair value	1,725,000	2,929,000	606,000	4,061,000
Other	6,766,000	3,539,000	6,761,000	4,582,000
Total net investment gains (losses)	3,163,000	2,946,000	2,895,000	5,858,000
NORCAL Group
Debt Securities, Available-for-Sale [Line Items]
Gain on fair value of contingent consideration	6,500,000	2,000,000.0	6,500,000	3,000,000.0
Corporate Debt
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	(4,000)	48,000	1,312,000	2,984,000
Asset-backed securities
Debt Securities, Available-for-Sale [Line Items]
Total impairment losses:	$ 5,000	$ 5,000	$ (189,000)	$ 8,000