Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative [Line Items]
Portion of ending balance of gain (loss) expected to be reclassified into earnings over the next twelve months, after-tax	$ (9)
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning balance, after-tax	(10)	$ (13)	$ (6)	$ (48)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	(13)	(1)	(24)	15
Clearance of hedge results to earnings, after-tax	0	(1)	7	18
Ending balance, after-tax	$ (23)	$ (15)	$ (23)	$ (15)