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Investments (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 [Line Items]
Net investment income earned	$ 63,889	$ 93,032	$ 206,713	$ 246,479
Investment Expense	(4,234)	(5,218)	(13,571)	(14,314)
Fixed Income Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	68,236	51,683	184,305	157,114
Commercial Mortgage Loans [Member]
Net Investment Income [Line Items]
Net investment income earned	1,600	683	3,762	1,892
Equity Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	2,604	2,955	7,661	8,425
Short-Term Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	1,152	64	1,660	204
Other Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	(5,469)	42,865	22,896	93,158
Alternative Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	$ (5,600)	$ 42,800	$ 22,800	$ 92,900

X

- Definition

Amount of expenses related to the generation of investment income.

+ References

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)
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
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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
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-Name Accounting Standards Codification
-Topic 944
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-Section S99
-Paragraph 1
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