Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Derivative [Line Items]
Portion of ending balance expected to be reclassified into earnings over the next twelve months, after-tax	$ (30)
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning Balance	(29)	29	3	41
Additions and revaluations of derivatives designated as cash flow hedges	(9)	(5)	(24)	15
Clearance of hedge results to earnings	1	(6)	(16)	(38)
Ending Balance	$ (37)	$ 18	$ (37)	$ 18