Investments - Holding gains (losses) on equity securities still held (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	$ (33)	$ (9)	$ (123)	$ 123
Realized gains (losses) on securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	(26)	(16)	(119)	82
Investment income
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	$ (7)	$ 7	$ (4)	$ 41