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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		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Net investment income earned		$ 83,731	$ 34,444	$ 153,447	$ 90,411
Carrying Value		330,479		330,479		$ 266,322
Alternative Investments [Member]
Net investment income earned		29,900	$ (16,000)	50,100	$ (9,700)
Other Securities [Member]
Carrying Value		33,450		33,450		35,370
Remaining Commitment		0		0		0
Maximum Exposure to Loss	[1]	33,450		33,450		35,370
Alternative Investments [Member]
Carrying Value		297,029		297,029		230,952
Remaining Commitment		222,903		222,903		215,728
Maximum Exposure to Loss	[1]	519,932		519,932		446,680
Alternative Investments [Member] | Private Equity Funds [Member]
Carrying Value		218,385		218,385		157,276
Remaining Commitment		110,998		110,998		100,905
Maximum Exposure to Loss	[1]	329,383		329,383		258,181
Alternative Investments [Member] | Private Credit Funds [Member]
Carrying Value		58,674		58,674		54,017
Remaining Commitment		96,132		96,132		98,330
Maximum Exposure to Loss	[1]	154,806		154,806		152,347
Alternative Investments [Member] | Real Assets [Member]
Carrying Value		19,970		19,970		19,659
Remaining Commitment		15,773		15,773		16,493
Maximum Exposure to Loss	[1]	35,743		35,743		36,152
Other Investments [Member]
Carrying Value		330,479		330,479		266,322
Remaining Commitment		222,903		222,903		215,728
Maximum Exposure to Loss	[1]	$ 553,382		$ 553,382		$ 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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This item represents contractual obligations to invest additional amounts on our other investment portfolio. These additional investments may or may not be required.

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No definition available.

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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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-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

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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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