Restructuring Charges (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges	$ 59	$ 96	$ 232	$ 331	$ 0
Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				331
Payments for Restructuring			$ 193	106
Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				172
2015 Plan [Member]
Restructuring Cost and Reserve [Line Items]
Increase in expected positions eliminated, percentage			75.00%
2015 Plan [Member] | Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			$ 232	58
2015 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				58
Severance Costs			149	58
Payments for Restructuring			168
2015 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges			19
Asset Impairment Charges			38
Payments for Restructuring			12
2014 Plan [Member] | Severance and Other Restructuring Liabilities [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				273
2014 Plan [Member] | Employee Severance [Member]
Restructuring Cost and Reserve [Line Items]
Severance Costs				114
Payments for Restructuring			7
2014 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Severance and Restructuring Charges				24
Payments for Restructuring			6
2014 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				$ 135
YEMEN | 2015 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges			26
Other Countries [Member] | 2015 Plan [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Asset Impairment Charges			$ 64