Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,077	$ 1,018
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	558	512
Equity securities	655	586
Equity securities, fair value in excess of cost	97	74
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	389	422
Equity securities	422	432
Equity securities, fair value in excess of cost	33	10
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	947	934
Equity securities	1,077	1,018
Equity securities, fair value in excess of cost	$ 130	$ 84