Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,008	$ 1,010
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	595	556
Equity securities	579	553
Equity securities, fair value in excess of cost	(16)	(3)
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	434	436
Equity securities	429	457
Equity securities, fair value in excess of cost	(5)	21
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	1,029	992
Equity securities	1,008	1,010
Equity securities, fair value in excess of cost	$ (21)	$ 18