Restructuring and Transformation Charges (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges	$ 27	$ 34	$ 90	$ 140
Asset Impairment Charges	50		50
Transformation Plan [Member]
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges	27		90
Transformation Plan [Member] | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Other restructuring costs	21		44
Transformation Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs	6		$ 46
Transformation Plan [Member] | Other Restructuring Less Asset Write-Offs [Member]
Restructuring Cost and Reserve [Line Items]
Other restructuring costs	$ 21
2016-17 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges		34		140
2016-17 Plan [Member] | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Other restructuring costs		19		69
Asset Impairment Charges				12
2016-17 Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs		15		71
2016-17 Plan [Member] | Other Restructuring excluding write-downs [Member]
Restructuring Cost and Reserve [Line Items]
Other restructuring costs		$ 19		$ 57