Investments - Equity securities reported at fair value (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,022	$ 1,042
Common stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	496	491
Equity securities	578	586
Equity securities, fair value in excess of cost	82	95
Perpetual preferred stocks
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	407	403
Equity securities	444	456
Equity securities, fair value in excess of cost	37	53
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities, at cost	903	894
Equity securities	1,022	1,042
Equity securities, fair value in excess of cost	$ 119	$ 148