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Investment Information - Net investment income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net investment income:
Gross investment income		$ 135,176	$ 151,965	$ 261,142	$ 320,291
Investment expenses		(23,563)	(20,480)	(50,673)	(43,653)
Net investment income		111,613	131,485	210,469	276,638
Fixed maturities
Net investment income:
Gross investment income		88,625	105,391	179,251	220,238
Term loans
Net investment income:
Gross investment income		16,879	20,512	31,607	43,682
Equity securities
Net investment income:
Gross investment income		8,584	6,219	14,234	12,226
Short-term investments
Net investment income:
Gross investment income		1,138	3,383	1,745	8,279
Other
Net investment income:
Gross investment income	[1]	$ 19,950	$ 16,460	$ 34,305	$ 35,866
[1] Includes income distributions from investment funds and other items.

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

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