Income taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, subject to expiry	$ 390
Operating Loss carryforwards, not subject to expiration	734
Tax credit carryforward, amount	2,603
Tax credit carryforward, amount, subject to expiration	88
Tax credit carryforward, amount, not subject to expiry	2,515
Valuation allowance	1,059	$ 914	$ 737	$ 578
Undistributed earnings	18,600
Unrecognized tax benefits that would impact effective tax rate	589	627
Accrued interest	101	84
Interest and penalties	20	$ 14	$ 5
Foreign tax jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,087
State and local jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 37