Derivative Instruments Outstanding Trading Contracts (Details) - Jun. 30, 2015 - Forward Contracts [Member] gal in Thousands	$ / gal gal
Sales [Member]
Derivative [Line Items]
Quantity In Gallons | gal	4,620
Weighted Average Contract Prices	0.4760
Sales [Member] | Minimum [Member]
Derivative [Line Items]
Estimated Market Prices	0.3475
Sales [Member] | Maximum [Member]
Derivative [Line Items]
Estimated Market Prices	0.5288
Purchase [Member]
Derivative [Line Items]
Quantity In Gallons | gal	4,620
Weighted Average Contract Prices	0.4322
Purchase [Member] | Minimum [Member]
Derivative [Line Items]
Estimated Market Prices	0.3550
Purchase [Member] | Maximum [Member]
Derivative [Line Items]
Estimated Market Prices	0.5025