Derivatives (Outstanding Derivative Balances) (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Other Current Assets [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	$ 63	$ 73
Cash Collateral	11	19
Total Derivative Balance	72	88
Netting	(2)	(4)
Other Noncurrent Assets [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	130	178
Cash Collateral	0	0
Total Derivative Balance	128	165
Netting	(2)	(13)
Other Current Liabilities [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	(84)	(78)
Cash Collateral	34	26
Total Derivative Balance	(48)	(48)
Netting	2	4
Other Noncurrent Liabilities [Member
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	(145)	(140)
Cash Collateral	24	9
Total Derivative Balance	(119)	(118)
Netting	2	13
Gross Derivative Balance [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	(36)	33
Netting [Member]
Derivatives And Hedging Activities [Line Items]
Netting	0	0
Cash Collateral [Member
Derivatives And Hedging Activities [Line Items]
Cash Collateral	69	54
Total Derivatve Balance [Member]
Derivatives And Hedging Activities [Line Items]
Total Derivative Balance	$ 33	$ 87