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Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount and Maximum Exposure to Loss Associated With Each Strategy) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Net investment income earned		$ 69,716	$ 55,967
Carrying Value		290,153		$ 266,322
Alternative Investments [Member]
Net investment income earned		20,200	$ 6,300
Other Securities [Member]
Carrying Value		31,613		35,370
Remaining Commitment		0		0
Maximum Exposure to Loss	[1]	31,613		35,370
Alternative Investments [Member]
Carrying Value		258,540		230,952
Remaining Commitment		218,033		215,728
Maximum Exposure to Loss	[1]	476,573		446,680
Alternative Investments [Member] | Private Equity Funds [Member]
Carrying Value		182,032		157,276
Remaining Commitment		104,070		100,905
Maximum Exposure to Loss	[1]	286,102		258,181
Alternative Investments [Member] | Private Credit Funds [Member]
Carrying Value		56,819		54,017
Remaining Commitment		98,072		98,330
Maximum Exposure to Loss	[1]	154,891		152,347
Alternative Investments [Member] | Real Assets [Member]
Carrying Value		19,689		19,659
Remaining Commitment		15,891		16,493
Maximum Exposure to Loss	[1]	35,580		36,152
Other Investments [Member]
Carrying Value		290,153		266,322
Remaining Commitment		218,033		215,728
Maximum Exposure to Loss	[1]	$ 508,186		$ 482,050
[1] The maximum exposure to loss includes both the carry value of these investments and the related remaining commitments. In addition, tax credits that have been previously recognized in Other securities are subject to the risk of recapture, which we do not consider significant.

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- Definition

This item represents contractual obligations to invest additional amounts on our other investment portfolio. These additional investments may or may not be required.

+ References

No definition available.

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- Definition

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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- Definition

Amount of investments classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f,g))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
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-URI http://asc.fasb.org/extlink&oid=121559654&loc=d3e5747-111685

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 810
-SubTopic 10
-Section 50
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