Acquisitions and Divestitures - 2017 Divestitures (Details) $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2017 USD ($) employee	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Net loss on divestitures of businesses										$ (109)	$ 57	$ 3
Sales		$ 3,472	$ 3,524	$ 3,573	$ 3,445	$ 3,271	$ 3,236	$ 3,261	$ 3,192	$ 14,014	12,960	12,394
Slim Aluminium
Business Acquisition [Line Items]
Cash expense related to divestiture of business	$ 10
Guarantee payments to third party	$ 5
Sales											54	$ 165
Number of employees | employee	312
Slim Aluminium | Restructuring and Other Charges
Business Acquisition [Line Items]
Net loss on divestitures of businesses											$ 60