Property, Plant and Equipment Property, Plant and Equipment - (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Land	$ 433	$ 397
Buildings	2,619	2,323
Machinery and equipment	13,449	12,278
Construction in progress	721	887
Property, plant and equipment, gross	17,222	15,885
Accumulated depreciation	(10,078)	(9,125)
Property plant and equipment, net before spare parts	7,144	6,760
Spare parts	307	280
Property, plant and equipment, net	7,451	7,040
Owned
Property, Plant and Equipment [Line Items]
Land	433	397
Buildings	2,589	2,288
Machinery and equipment	13,403	12,232
Construction in progress	721	887
Property, plant and equipment, gross	17,146	15,804
Accumulated depreciation	(10,047)	(9,102)
Property plant and equipment, net before spare parts	7,099	6,702
Spare parts	307	280
Property, plant and equipment, net	7,406	6,982
Capital Leases
Property, Plant and Equipment [Line Items]
Land	0	0
Buildings	30	35
Machinery and equipment	46	46
Construction in progress	0	0
Property, plant and equipment, gross	76	81
Accumulated depreciation	(31)	(23)
Property plant and equipment, net before spare parts	45	58
Spare parts	0	0
Property, plant and equipment, net	$ 45	$ 58
Building and Building Improvements | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Building and Building Improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	45 years
Machinery and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Machinery and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	40 years