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Investment Information - Net investment income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net investment income:
Gross investment income		$ 106,803	$ 150,854	$ 367,945	$ 471,145
Investment expenses		(18,608)	(22,342)	(69,281)	(65,995)
Net investment income		88,195	128,512	298,664	405,150
Fixed maturities
Net investment income:
Gross investment income		75,964	98,344	255,215	318,582
Term loans
Net investment income:
Gross investment income		1,736	22,459	33,343	66,141
Equity securities
Net investment income:
Gross investment income		9,867	6,659	24,101	18,885
Short-term investments
Net investment income:
Gross investment income		1,858	1,332	3,603	9,611
Other
Net investment income:
Gross investment income	[1]	$ 17,378	$ 22,060	$ 51,683	$ 57,926
[1] Includes income distributions from investment funds and other items.

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- Definition

Amount before accretion (amortization) of purchase discount (premium) of interest income and dividend income on nonoperating securities.

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