Risk Management Energy Commodity Price Risk Management (Details) - Energy Related Derivative [Member] - Forward Contracts [Member]	Sep. 30, 2015 Bcf MMBbls
Crude oil fixed price | Derivatives designated as hedging contracts
Derivative [Line Items]
Net open position long/(short)	(23.0)
Crude oil fixed price | Derivatives not designated as hedging contracts
Derivative [Line Items]
Net open position long/(short)	(1.8)
Crude oil basis | Derivatives designated as hedging contracts
Derivative [Line Items]
Net open position long/(short)	(9.4)
Crude oil basis | Derivatives not designated as hedging contracts
Derivative [Line Items]
Net open position long/(short)	(1.7)
Natural gas fixed price | Derivatives designated as hedging contracts
Derivative [Line Items]
Net open position long/(short) | Bcf	(41.2)
Natural gas fixed price | Derivatives not designated as hedging contracts
Derivative [Line Items]
Net open position long/(short) | Bcf	(20.6)
Natural gas basis | Derivatives designated as hedging contracts
Derivative [Line Items]
Net open position long/(short) | Bcf	(16.7)
Natural gas basis | Derivatives not designated as hedging contracts
Derivative [Line Items]
Net open position long/(short) | Bcf	(15.0)
NGL and other fixed price | Derivatives not designated as hedging contracts
Derivative [Line Items]
Net open position long/(short)	(1.9)