Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative [Line Items]
Derivative, Remaining Maturity	2 years
Portion of ending balance of gain (loss) expected to be reclassified into earnings over the next twelve months, after-tax	$ 8
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning balance, after-tax	7	$ (24)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	2	10
Clearance of hedge results to earnings, after-tax	(5)	7
Ending balance, after-tax	$ 4	$ (7)