Derivative Instruments - Outstanding Trading Contracts (Details) gal in Thousands, bbl in Thousands	Jun. 30, 2016 gal bbl $ / gal
Sales [Member] | Minimum [Member] | Forward Contracts [Member]
Derivative [Line Items]
Estimated Market Prices	0.5213
Sales [Member] | Maximum [Member] | Forward Contracts [Member]
Derivative [Line Items]
Estimated Market Prices	0.5213
Purchase [Member] | Forward Contracts [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | gal	421
Weighted Average Contract Prices	0.5388
Purchase [Member] | Future [Member]
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | bbl	20
Estimated Market Prices	48.80
Weighted Average Contract Prices	47.9000
Purchase [Member] | Minimum [Member] | Forward Contracts [Member]
Derivative [Line Items]
Estimated Market Prices	0.5375
Purchase [Member] | Maximum [Member] | Forward Contracts [Member]
Derivative [Line Items]
Estimated Market Prices	0.5375