Supplemental financial information - Property, plant and equipment at cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost	$ 4,923	$ 5,465
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost	127	127
Buildings and improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost	$ 2,753	2,789
Buildings and improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost, depreciable lives	5 years
Buildings and improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost, depreciable lives	40 years
Machinery and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost	$ 2,043	$ 2,549
Machinery and equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost, depreciable lives	2 years
Machinery and equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment at cost, depreciable lives	10 years