Investments - Holding gains (losses) on equity securities still held (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Realized gains (losses) on securities	$ (116)	$ 110	$ (75)
Investment income	733	742	467
Equity securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Realized gains (losses) on securities	(96)	110	(70)
Equity securities still owned | Equity securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Net holding gains (losses) on equity securities	(90)	119	(32)
Realized gains (losses) on securities | Equity securities still owned | Equity securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Realized gains (losses) on securities	(95)	65	(44)
Investment income | Equity securities still owned | Equity securities
Holding Gains (Losses) on Equity Securities Still Held [Line Items]
Investment income	$ 5	$ 54	$ 12