Reinsurance (Effect of Reinsurance on Net Premiums and Claims and Other Policy Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Policyholder Benefits and Claims Incurred, Net [Abstract]
Claims and other policy benefits	$ 16,903.0	$ 13,872.0	$ 11,982.0
Premiums Earned, Net [Abstract]
Direct Premiums Earned	2,919.0	1,477.0	26.0
Assumed Premiums Earned	15,573.0	14,281.0	13,830.0
Ceded Premiums Earned	(649.0)	(673.0)	(778.0)
Net premiums	17,843.0	15,085.0	13,078.0
Life Insurance Product Line [Member]
Policyholder Benefits and Claims Incurred, Net [Abstract]
Policyholder Benefits and Claims Incurred, Direct	3,257.0	1,577.0	73.0
Policyholder Benefits and Claims Incurred, Assumed	13,997.0	12,912.0	12,867.0
Policyholder Benefits and Claims Incurred, Ceded	(383.0)	(679.0)	(667.0)
Claims and other policy benefits	$ 16,871.0	$ 13,810.0	$ 12,273.0

Amount of earned premiums assumed from other entities.

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Amount of earned premiums ceded to other entities.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
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-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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-URI https://asc.fasb.org/1943274/2147479032/944-605-50-1

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Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

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Amount, before effect of policies assumed or ceded, of expense related to provision for policy benefits and costs incurred.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

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Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

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Amount of policy benefits and costs incurred for policies assumed.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-3

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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

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