Investments (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Net Investment Income [Line Items]
Gross investment income	$ 549	$ 531	$ 895	$ 1,118
Investment expense	(15)	(16)	(32)	(32)
Net investment income	534	515	863	1,086
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	430	455	868	910
Equity securities
Net Investment Income [Line Items]
Gross investment income	50	16	6	46
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	44	37	(26)	113
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	14	12	28	24
Short term investments
Net Investment Income [Line Items]
Gross investment income	1	9	8	19
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	8	2	9	4
Other
Net Investment Income [Line Items]
Gross investment income	$ 2	$ 0	$ 2	$ 2

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.

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Amount of expenses related to the generation of investment income.

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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

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