Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,018	$ 1,010
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	512	556
Equity securities	586	553
Equity securities, fair value in excess of cost	74	(3)
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	422	436
Equity securities	432	457
Equity securities, fair value in excess of cost	10	21
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	934	992
Equity securities	1,018	1,010
Equity securities, fair value in excess of cost	$ 84	$ 18