Derivative Instruments Outstanding Trading Contracts (Details) (Forward Contracts [Member])	Mar. 31, 2015 gal
Sales [Member]
Derivative [Line Items]
Quantity In Gallons	420,000
Weighted Average Contract Prices	0.4788
Sales [Member] | Minimum [Member]
Derivative [Line Items]
Estimated Market Prices	0.4788
Sales [Member] | Maximum [Member]
Derivative [Line Items]
Estimated Market Prices	0.4788
Purchase [Member]
Derivative [Line Items]
Quantity In Gallons	421,000
Weighted Average Contract Prices	0.4789
Purchase [Member] | Minimum [Member]
Derivative [Line Items]
Estimated Market Prices	0.4775
Purchase [Member] | Maximum [Member]
Derivative [Line Items]
Estimated Market Prices	0.4775