Summary of Significant Accounting Policies - Adjustments Made Due to ASU 2014-09 Impact on Income Statement (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	$ 526	$ 567	$ 1,692	$ 1,729
Cost of sales	(428)	(458)	(1,371)	(1,387)
Operating loss	(58)	$ (16)	(122)	$ (39)
Balances without adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	525		1,691
Cost of sales	(427)		(1,370)
Operating loss	(58)		(122)
Effect of Changes | ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net sales	1		1
Cost of sales	(1)		(1)
Operating loss	$ 0		$ 0