Property, Plant and Equipment (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2017
Property, plant and equipment
Property, plant and equipment, gross	$ 7,076			$ 7,076			$ 7,386
Accumulated depreciation	(2,603)			(2,603)			(2,776)
Net property, plant and equipment	4,473			4,473			4,610
Depreciation expense	129	$ 153		254	$ 260
Noncash capital expenditures				97			124
Land
Property, plant and equipment
Property, plant and equipment, gross	170			170			172
Buildings
Property, plant and equipment
Property, plant and equipment, gross	1,318			1,318			1,390
Machinery and equipment
Property, plant and equipment
Property, plant and equipment, gross	5,034			5,034			5,282
Construction-in-progress
Property, plant and equipment
Property, plant and equipment, gross	$ 554			$ 554			$ 542
Rexam
Property, plant and equipment
Catch up depreciation		$ 35	$ 11			$ 24