Financial and Other Derivative Instruments Financial and Other Derivative Instruments (Netting Offsets Reconciliation to Balance Sheet) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative Asset, Gross	$ 693	$ 833
Derivative Liability, Gross	(787)	(936)
Derivative Assets, Current	68	99
Derivative Assets, Noncurrent	29	27
Derivative Liabilities, Current	(134)	(195)
Derivative Liabilities, Noncurrent	(19)	(43)
Current Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	605	691
Noncurrent Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	88	142
Current Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	(696)	(773)
Noncurrent Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	(91)	(163)
Collateral Adjustment [Member] | Current Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	(4)	(26)
Collateral Adjustment [Member] | Noncurrent Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	0	0
Collateral Adjustment [Member] | Current Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	29	12
Collateral Adjustment [Member] | Noncurrent Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	13	5
Counterparty Netting [Member] | Current Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	(533)	(566)
Counterparty Netting [Member] | Noncurrent Derivative Asset [Member]
Derivative [Line Items]
Derivative Asset, Gross	(59)	(115)
Counterparty Netting [Member] | Current Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	533	566
Counterparty Netting [Member] | Noncurrent Derivative Liability [Member]
Derivative [Line Items]
Derivative Liability, Gross	$ 59	$ 115