Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative [Line Items]
Portion of ending balance expected to be reclassified into earnings over the next twelve months, after-tax	$ (24)
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance	(12)	18	3	41
Additions and revaluations of derivatives designated as cash flow hedges	(6)	24	(15)	20
Clearance of hedge results to earnings	(11)	(13)	(17)	(32)
Ending Balance	$ (29)	$ 29	$ (29)	$ 29