Investment and derivative contract gains (losses) - Narrative (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Sales of equity securities	$ 33,664	$ 15,849	$ 38,756
Taxable gains (loss) on sales of equity securities	$ 769	$ 3,600	$ 6,200