Variable interest entities - Schedule of results of variable interest entities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Variable Interest Entity [Line Items]
Gross profit	$ 12,701	$ 11,963	$ 10,815
Net loss	3,492	3,178	3,862
Net cash provided by operating activities	4,989	5,017	3,800
Variable interest entity, primary beneficiary
Variable Interest Entity [Line Items]
Total revenues	359	446	544
Total cost of revenues	(339)	(416)	(479)
Gross profit	20	30	65
Net loss	(40)	(325)	(24)
Net cash provided by operating activities	$ 10	$ 24	$ 12