Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,007	$ 1,010
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	562	556
Equity securities	588	553
Equity securities, fair value in excess of cost	26	(3)
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	419	436
Equity securities	419	457
Equity securities, fair value in excess of cost	0	21
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	981	992
Equity securities	1,007	1,010
Equity securities, fair value in excess of cost	$ 26	$ 18