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Investments (Net Investment Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net Investment Income [Line Items]
Net investment income earned	$ 72,602	$ 69,716
Investment Expense	(4,117)	(3,627)
Fixed Income Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	53,925	52,823
Commercial Mortgage Loans [Member]
Net Investment Income [Line Items]
Net investment income earned	970	514
Equity Securities [Member]
Net Investment Income [Line Items]
Net investment income earned	2,418	2,488
Short-Term Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	101	85
Other Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	19,305	17,433
Alternative Investments [Member]
Net Investment Income [Line Items]
Net investment income earned	$ 19,100	$ 20,200

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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