Investments - Schedule of sources of net investment income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net Investment Income [Line Items]
Investment income	$ 173	$ 124	$ 529	$ 319
Equity in earnings of partnerships and similar investments	73	36	222	53
Investment expenses	(4)	(2)	(8)	(5)
Net investment income	169	122	521	314
Investment income
Net Investment Income [Line Items]
Change in fair value of equity securities	7	(2)	41	(10)
Fixed maturities
Net Investment Income [Line Items]
Investment income	73	73	217	232
Other
Net Investment Income [Line Items]
Investment income	14	8	28	17
Investment income \| Equity securities
Net Investment Income [Line Items]
Investment income	$ 6	$ 9	$ 21	$ 27

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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