Derivative Instruments and Hedging Activities (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Document Period End Date	Mar. 31, 2014
Derivative Asset, Fair Value	$ 11		$ 17
Derivative Liability, Fair Value	111		75
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(75)	(72)
Realized Mark-to-Market (Gain) Loss	33	(7)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(42)	(79)
AOCL amount, net of tax, to be reclassified to interest expense over life of debt	(24)
Current Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	0		1
Current Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	95		65
Noncurrent Assets
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	11		16
Noncurrent Liabilities
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	16		10
Crude Oil [Member]
Derivatives, Fair Value [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(55)	(49)
Realized Mark-to-Market (Gain) Loss	27	8
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(28)	(41)
Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(20)	(23)
Realized Mark-to-Market (Gain) Loss	6	(15)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	$ (14)	$ (38)