Investments - Holding gains (losses) on equity securities still held (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	$ (91)	$ 44	$ (100)	$ 132
Realized gains (losses) on securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	(82)	36	(96)	98
Investment income
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Holding gains (losses) on equity securities still held	$ (9)	$ 8	$ (4)	$ 34