Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net Investment Income [Line Items]
Investment income	$ 578	$ 593	$ 1,601	$ 1,727
Equity in earnings of partnerships and similar investments	66	43	37	109
Investment expenses	(6)	(5)	(17)	(17)
Net Investment Income, Total	572	588	1,584	1,710
Fixed maturities
Net Investment Income [Line Items]
Investment income	473	475	1,449	1,422
Other
Net Investment Income [Line Items]
Investment income	26	36	72	95
Accounting Standards Update 2016-01 \| Equity securities
Net Investment Income [Line Items]
Investment income	(3)	17	(6)	35
Investment income \| Equity securities
Net Investment Income [Line Items]
Investment income	$ 16	$ 22	$ 49	$ 66

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 income (loss) for proportionate share of equity method investee's income (loss).

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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.

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