Net Investment Income (Net Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Net Investment Income [Line Items]
Gross investment income	$ 789,106	$ 679,414	$ 592,946
Investment expense	(9,921)	(7,796)	(9,125)
Net investment income	779,185	671,618	583,821
Fixed maturity securities, including cash and cash equivalents and loans receivable
Net Investment Income [Line Items]
Gross investment income	549,281	382,001	426,563
Investment funds
Net Investment Income [Line Items]
Gross investment income	145,099	220,014	54,253
Arbitrage trading account
Net Investment Income [Line Items]
Gross investment income	45,213	37,676	77,931
Real estate
Net Investment Income [Line Items]
Gross investment income	(3,087)	7,703	24,027
Equity securities
Net Investment Income [Line Items]
Gross investment income	$ 52,600	$ 32,020	$ 10,172

Amount of expenses related to the generation of investment income.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.9)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(2))
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Investment Income (Loss), Interest and Dividend

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