Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash, Cash Equivalents and Restricted Cash
Cash and cash equivalents	$ 598	$ 448	$ 556	$ 597
Current restricted cash	$ 13	$ 10	$ 6	$ 9
Restricted Cash and Cash Equivalents, Current, Asset, Statement of Financial Position [Extensible List]	Other Assets, Current	Other Assets, Current	Other Assets, Current	Other Assets, Current
Noncurrent restricted cash		$ 1	$ 1	$ 1
Restricted Cash and Cash Equivalents, Noncurrent, Asset, Statement of Financial Position [Extensible List]	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent	Other Assets, Noncurrent
Total cash, cash equivalents and restricted cash	$ 611	$ 459	$ 563	$ 607
Other Non-cash items
PP&E acquired but not yet paid	98	$ 124
Rexam
Other Non-cash items
Payment of indemnification guarantees	$ 45