Investment Information - Net investment income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Net investment income:
Gross investment income		$ 145,777	$ 106,803	$ 372,286	$ 367,945
Investment expenses		(17,137)	(18,608)	(56,818)	(69,281)
Net investment income		128,640	88,195	315,468	298,664
Fixed maturities
Net investment income:
Gross investment income		123,568	75,964	310,963	255,215
Term loans
Net investment income:
Gross investment income		88	1,736	2,106	33,343
Equity securities
Net investment income:
Gross investment income		4,261	9,867	16,620	24,101
Short-term investments
Net investment income:
Gross investment income		9,304	1,858	15,999	3,603
Other
Net investment income:
Gross investment income	[1]	$ 8,556	$ 17,378	$ 26,598	$ 51,683

[1] Includes income distributions from investment funds and other items.