Derivatives And Hedging Activities (Outstanding Derivative Balances) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Other Current Assets [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	$ 97	$ 73
Cash Collateral	25	19
Total Derivative Balances	118	88
Derivative Liability Offsetting Derivative Asset	(4)	(4)
Other Noncurrent Assets [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	172	178
Cash Collateral	0	0
Total Derivative Balances	170	165
Derivative Liability Offsetting Derivative Asset	(2)	(13)
Other Current Liabilities [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance		(78)
Gross Derivative Balance	(102)
Cash Collateral	44	26
Total Derivative Balances	(54)	(48)
Derivative Asset Offsetting Derivative Liability	4	4
Other Noncurrent Liabilities [Member]
Derivatives And Hedging Activities [Line Items]
Gross Derivative Balance	(140)	(140)
Cash Collateral	21	9
Total Derivative Balances	(117)	(118)
Derivative Asset Offsetting Derivative Liability	2	13
Gross Derivative Balance [Member]
Derivatives And Hedging Activities [Line Items]
Total Gross Derivative Balance	27	33
Netting [Member]
Derivatives And Hedging Activities [Line Items]
Derivative Asset Offsetting Derivative Liability	0	0
Cash Collatera [lMember]
Derivatives And Hedging Activities [Line Items]
Cash Collateral	90	54
Total Derivatve Balance [Member]
Derivatives And Hedging Activities [Line Items]
Total Derivative Balances	$ 117	$ 87