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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Portion of ending balance of gain (loss) expected to be reclassified into earnings over the next twelve months, after-tax	$ 7
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning balance, after-tax	10	$ (10)	$ (24)	$ (6)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	(2)	(13)	21	(24)
Clearance of hedge results to earnings, after-tax	0	0	11	7
Ending balance, after-tax	$ 8	$ (23)	$ 8	$ (23)