Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 751	$ 1,018
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	304	512
Equity securities	336	586
Equity securities, fair value in excess of cost	32	74
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	380	422
Equity securities	415	432
Equity securities, fair value in excess of cost	35	10
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	684	934
Equity securities	751	1,018
Equity securities, fair value in excess of cost	$ 67	$ 84