Financial Instruments (Effect of Cash Flows Hedges on Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative [Line Items]
Derivative, Remaining Maturity			2 years
Portion of ending balance of loss expected to be reclassified into earnings over the next twelve months, after-tax			$ (2)
Cash Flow Hedging [Member]
Derivative [Line Items]
Beginning balance, after-tax	$ 4	$ (7)	7	$ (24)
Additions and revaluations of derivatives designated as cash flow hedges, after-tax	0	13	2	23
Clearance of hedge results to earnings, after-tax	(8)	4	(13)	11
Ending balance, after-tax	$ (4)	$ 10	$ (4)	$ 10