Restructuring Charges (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	$ 183	$ 280	$ 232
Asset Impairment Charges		436
Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and Related Cost, Incurred Cost	171
Payments for Restructuring	167
2016-17 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges	183
2016-17 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs	109
Restructuring and Related Cost, Incurred Cost	109
Payments for Restructuring	137
2016-17 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other Restructuring Costs	74
Asset Impairment Charges	12
Restructuring and Related Cost, Incurred Cost	62
Payments for Restructuring	26
2016-17 Plan [Member] | Other Restructuring excluding write-downs [Member]
Restructuring Cost and Reserve [Line Items]
Other Restructuring Costs	$ 62
2016 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		280
2016 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs		196
2016 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other Restructuring Costs		84
Asset Impairment Charges		40
2016 Plan [Member] | Other Restructuring excluding write-downs [Member]
Restructuring Cost and Reserve [Line Items]
Other Restructuring Costs		$ 44
2015 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			232
2015 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs			149
2015 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			19
Other Restructuring Costs			83
2015 Plan [Member] | Impaired Assets to be Disposed of by Method Other than Sale, Asset Name [Domain]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges			$ 64