Pension plans - Additional tabular disclosures (Detail) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Discount rate applicable to PBOs	5.20%	2.70%	2.30%
Expected long-term rate of return on plan assets	5.90%	6.10%	6.20%
Rate of compensation increase	2.50%	2.60%	2.60%
Discount rate applicable to net periodic pension expense	2.90%	2.40%	3.10%
Amounts recognized in other comprehensive income:
Accumulated other comprehensive income (loss), beginning of year	$ (485)	$ (2,251)
Amount included in net periodic pension expense	123	170
Actuarial gains (losses) and other	(376)	1,596
Accumulated other comprehensive income (loss), end of year	$ (738)	$ (485)	$ (2,251)