Risk Management Energy Commodity Price Risk Managment (Details)	Jun. 30, 2013
Crude Oil [Member]
Derivative [Line Items]
Net open position long/(short)	(2,400,000)
Natural Gas Fixed Price [Member]
Derivative [Line Items]
Net open position long/(short)	(32,800,000,000)
Net open position long/(short)	(500,000,000)
Natural Gas Basis [Member]
Derivative [Line Items]
Net open position long/(short)	(32,800,000,000)
Net open position long/(short)	1,600,000,000
Crude Oil Fixed Price [Member]
Derivative [Line Items]
Net open position long/(short)	(22,000,000)
Net open position long/(short)	700,000
Natural Gas Liquids Fixed Price [Member]
Derivative [Line Items]
Net open position long/(short)	500,000