Investment and derivative contract gains (losses) - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Jan. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Sales of equity securities	$ 13,283	$ 9,724
Taxable gains (losses) on sales of equity securities	2,200	$ (739)
Pilot Travel Centers LLC [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Investment gains from remeasurement	$ 3,000
Equity interest ownership percentage	38.60%		38.60%