Investments (Net Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Net Investment Income [Line Items]
Gross investment income	$ 947	$ 842
Less: Investment expenses	51	54
Net investment income	896	788
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	658	642
Equity securities
Net Investment Income [Line Items]
Gross investment income	2	3
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	166	158
Policy loans
Net Investment Income [Line Items]
Gross investment income	6	10
Limited partnerships and LLCs
Net Investment Income [Line Items]
Gross investment income	82	8
Cash, cash equivalents and short-term investments
Net Investment Income [Line Items]
Gross investment income	20	10
Other
Net Investment Income [Line Items]
Gross investment income	$ 13	$ 11

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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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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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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