Asset Impairment, Exit, and Restructuring Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Asset Impairment Charges And Exit Costs [Line Items]
Asset impairment, exit, and restructuring costs	$ 24	$ 23	$ 40	$ 33
Asset Impairment Charges	21	17	21	18
Restructuring Charges	1	4	2	12
Equity Method Investment, Other than Temporary Impairment			12
Corporate, Non-Segment [Member]
Asset Impairment Charges And Exit Costs [Line Items]
Restructuring Charges	$ 2	$ 2	$ 5	$ 3