Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Net Investment Income [Line Items]
Investment income	$ 166	$ 89	$ 356	$ 195
Equity in earnings of partnerships and similar investments	71	(6)	149	17
Investment expenses	(2)	(1)	(4)	(3)
Net Investment Income, Total	164	88	352	192
Investment income
Net Investment Income [Line Items]
Change in fair value of equity securities	8	9	34	(8)
Fixed maturities
Net Investment Income [Line Items]
Investment income	72	77	144	159
Other
Net Investment Income [Line Items]
Investment income	8	1	14	9
Investment income \| Equity securities
Net Investment Income [Line Items]
Investment income	$ 7	$ 8	$ 15	$ 18

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).

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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.

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

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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.

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