Restructuring and Transformation Charges (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges	$ 25	$ 75
Transformation Plan [Member]
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges	25
Transformation Plan [Member] | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Other restructuring costs	14
Transformation Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs	11
Transformation Plan [Member] | Other Restructuring Less Asset Write-Offs [Member]
Restructuring Cost and Reserve [Line Items]
Other restructuring costs	$ 14
2016-17 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Severance, asset impairment and other restructuring charges		75
2016-17 Plan [Member] | Other Restructuring
Restructuring Cost and Reserve [Line Items]
Other restructuring costs		41
Asset Impairment Charges		12
2016-17 Plan [Member] | Employee Severance
Restructuring Cost and Reserve [Line Items]
Severance costs		34
2016-17 Plan [Member] | Other Restructuring excluding write-downs [Member]
Restructuring Cost and Reserve [Line Items]
Other restructuring costs		$ 29