Income taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	May 31, 2021
Income Tax Disclosure [Abstract]
Effective income tax rate	16.80%	11.20%	12.60%	10.40%
Increase in unrecognized tax benefits resulting from tax positions taken during the current period	$ 50		$ 110
Proposed additional income tax					$ 3,600
Repatriation tax on proposed additional tax					$ 900