Investments (Net investment income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Net Investment Income [Line Items]
Gross investment income	$ 573	$ 440	$ 1,711	$ 1,355
Investment expense	(20)	(18)	(58)	(53)
Net investment income	553	422	1,653	1,302
Fixed maturity securities
Net Investment Income [Line Items]
Gross investment income	491	454	1,443	1,324
Equity securities
Net Investment Income [Line Items]
Gross investment income	9	2	42	(7)
Limited partnership investments
Net Investment Income [Line Items]
Gross investment income	28	(35)	108	(11)
Mortgage loans
Net Investment Income [Line Items]
Gross investment income	15	13	43	40
Short term investments
Net Investment Income [Line Items]
Gross investment income	23	4	51	6
Trading portfolio
Net Investment Income [Line Items]
Gross investment income	1	1	4	2
Other
Net Investment Income [Line Items]
Gross investment income	6	1	20	1
Common Stock
Net Investment Income [Line Items]
Net investment income (loss) recognized due to the change in fair value of common stock held as of September 30, 2023 and 2022	$ (3)	$ (18)	$ 2	$ (38)

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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