Sales and revenue recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2018
Revenue from External Customer [Line Items]
Receivables, Net, Current	$ 7,743	$ 6,399
Long term trade receivables from dealers and end users	674	639
Contract with Customer, Liability, Noncurrent	437	$ 396
Contract with Customer, Liability, Revenue Recognized	1,294
Revenue, Remaining Performance Obligation, Amount	$ 5,800
Period after which Collection of Future Income is Considered as Not Probable	120 days
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue from External Customer [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,500