Derivative Instruments and Hedging Activities (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	$ 170		$ 170		$ 47
Derivative Liability, Fair Value	2		2		83
Realized Mark-to-Market (Gain) Loss	1	(1)	24	(17)
Unrealized Mark-to-Market (Gain) Loss	(277)	(142)	(204)	160
Total (Gain) Loss on Commodity Derivative Instruments	(276)	(143)	(180)	143
Current Assets | Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	85		85		10
Current Liabilities | Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	2		2		76
Noncurrent Assets | Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value	85		85		37
Noncurrent Liabilities | Commodity Contract
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value	$ 0		$ 0		$ 7