Warranty and restructuring costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Restructuring
Balance at beginning of period	$ 2	$ 3
Obligations incurred		18	$ 13
Payments/uses	(2)	(19)
Balance at end of period		2	3
Warranty and after-sale service
Balance at beginning of period	41	40
Obligations incurred	1	3
Payments/uses	(4)	(2)
Balance at end of period	$ 38	$ 41	$ 40