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 [Line Items]
Gross investment income	$ 170,305	$ 87,366	$ 330,332	$ 264,757
Investment expense	(2,118)	(1,935)	(3,568)	(4,563)
Net investment income	168,187	85,431	326,764	260,194
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	96,996	105,843	191,673	233,861
Investment funds
Net Investment Income [Line Items]
Investment funds	61,311	(57,552)	100,246	(16,975)
Arbitrage trading account
Net Investment Income [Line Items]
Gross investment income	3,914	31,304	22,989	32,442
Equity securities
Net Investment Income [Line Items]
Gross investment income	872	5,045	2,032	11,141
Real estate
Net Investment Income [Line Items]
Gross investment income	$ 7,212	$ 2,726	$ 13,392	$ 4,288

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

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Amount of expenses related to the generation of investment income.

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Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities.

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Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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