Natural Gas Basis Contracts That are Not Designated for Hedge Accounting (Details) (Basis contracts [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012
Natural gas basis contracts not designated for hedge accounting [Abstract]
Derivative Liability, Fair Value, Total	$ (6)
July 2012 - September 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Derivative Liability, Fair Value, Total	(3)
October 2012 - December 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Derivative Liability, Fair Value, Total	$ (3)
Rocky Mountains [Member] | July 2012 - September 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Volume in MMMBtus	1,230
Weighted Average Differential	(0.91)
Rocky Mountains [Member] | October 2012 - December 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Volume in MMMBtus	1,230
Weighted Average Differential	(0.91)
Mid-Continent [Member] | July 2012 - September 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Volume in MMMBtus	4,600
Weighted Average Differential	(0.55)
Mid-Continent [Member] | October 2012 - December 2012 [Member]
Natural gas basis contracts not designated for hedge accounting [Abstract]
Volume in MMMBtus	4,600
Weighted Average Differential	(0.55)