Investments (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Net Investment Income [Line Items]
Gross investment income	$ 544	$ 465
Investment expense	(19)	(17)
Net investment income	525	448
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	470	429
Equity securities
Net Investment Income [Line Items]
Gross investment income	12	2
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	25	18
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	14	15
Short term investments
Net Investment Income [Line Items]
Gross investment income	15	0
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	3	1
Other
Net Investment Income [Line Items]
Gross investment income	5	0
Common Stock
Net Investment Income [Line Items]
Net investment income (loss) recognized due to the change in fair value of common stock held as of March 31, 2023 and 2022	$ (1)	$ (5)

Amount of unrealized and realized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126980263&loc=SL75117546-209714

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Amount, before 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

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-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.2)
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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
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+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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