Pension plans - Net periodic pension expense (Detail) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Components of net periodic pension expense
Service cost	$ 181	$ 257	$ 235
Interest cost	482	410	510
Expected return on plan assets	(975)	(1,008)	(955)
Amortization of actuarial losses and other	156	203	171
Net periodic pension expense	$ (156)	$ (138)	$ (39)