Pension plans - Additional tabular disclosures (Detail) - Pension Plans, Defined Benefit [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Discount rate applicable to PBOs	5.50%	5.00%	5.20%
Expected long-term rate of return on plan assets	5.90%	6.00%	5.90%
Rate of compensation increase	2.60%	2.60%	2.50%
Discount rate applicable to net periodic pension expense	5.10%	5.30%	2.90%
Amounts recognized in other comprehensive income:
Accumulated other comprehensive income (loss), beginning of the year	$ (161)	$ (738)
Amount included in net periodic pension expense	29	(12)
Actuarial gains (losses) and other	1,599	589
Accumulated other comprehensive income (loss), end of the year	$ 1,467	$ (161)	$ (738)