Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,048	$ 1,010
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	620	556
Equity securities	617	553
Equity securities, fair value in excess of cost	(3)	(3)
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	434	436
Equity securities	431	457
Equity securities, fair value in excess of cost	(3)	21
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	1,054	992
Equity securities	1,048	1,010
Equity securities, fair value in excess of cost	$ (6)	$ 18