Derivative Financial Instruments (Details 5) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Credit Risk
Number of clearing brokers, primarily utilized	2
Forward | Sales commitments
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	$ 18,339,000	$ 48,062,000
Liability Derivatives	4,080,000	34,474,000
Derivatives not designated as either fair value hedges or cash flow hedges | Product contracts | Maximum
Derivatives not designated as either fair value hedges or cash flow hedges
Aggregate units of products in a controlled trading program	250,000
Derivatives not designated as either fair value hedges or cash flow hedges | Foreign currency forward contract | Foreign Denominated Sales
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives		145,000
Liability Derivatives	175,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	18,339,000	48,207,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Purchase commitments
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	17,089,000	15,543,000
Liability Derivatives	1,612,000	31,351,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Purchase commitments | Gasoline and gasoline blendstocks
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	12,435,000	131,000
Liability Derivatives		27,604,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Purchase commitments | Crude Oil
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	4,654,000	15,127,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Purchase commitments | Residual Oil
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives		285,000
Liability Derivatives	288,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Purchase commitments | Distillates
Derivatives not designated as either fair value hedges or cash flow hedges
Liability Derivatives	85,000	2,171,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Sales commitments
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	1,250,000	32,519,000
Liability Derivatives	2,468,000	3,123,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Sales commitments | Gasoline and gasoline blendstocks
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives		30,928,000
Liability Derivatives	552,000	173,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Sales commitments | Distillates
Derivatives not designated as either fair value hedges or cash flow hedges
Liability Derivatives	1,916,000	2,950,000
Derivatives not designated as either fair value hedges or cash flow hedges | Forward | Sales commitments | Natural Gas
Derivatives not designated as either fair value hedges or cash flow hedges
Asset Derivatives	1,250,000	1,591,000
Liability Derivatives	$ 1,239,000	$ 1,576,000