Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 770	$ 751
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	312	304
Equity securities	341	336
Equity securities, fair value in excess of cost	29	32
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	391	380
Equity securities	429	415
Equity securities, fair value in excess of cost	38	35
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	703	684
Equity securities	770	751
Equity securities, fair value in excess of cost	$ 67	$ 67