Investments (Net investment income) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Net Investment Income [Line Items]
Gross investment income	$ 2,223	$ 1,999	$ 2,181
Investment expense	(64)	(64)	(63)
Net investment income	2,159	1,935	2,118
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	1,707	1,728	1,817
Equity securities
Net Investment Income [Line Items]
Gross investment income	83	65	85
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	362	121	180
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	61	57	51
Short term investments
Net Investment Income [Line Items]
Gross investment income	1	9	34
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	9	18	9
Other
Net Investment Income [Line Items]
Gross investment income	$ 0	$ 1	$ 5

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Amount of expenses related to the generation of investment income.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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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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