Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,042	$ 889
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	491	516
Equity securities	586	510
Equity securities, fair value in excess of cost	95	(6)
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	403	369
Equity securities	456	379
Equity securities, fair value in excess of cost	53	10
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	894	885
Equity securities	1,042	889
Equity securities, fair value in excess of cost	$ 148	$ 4