Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Derivative [Line Items]
Portion of ending balance of gain (loss) expected to be reclassified into earnings over the next twelve months, after-tax	$ (4)
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning balance, after-tax	(6)	(48)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	(16)	24
Clearance of hedge results to earnings, after-tax	4	11
Ending balance, after-tax	$ (18)	$ (13)