Financial Instruments (Details Textual) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2015 USD ($) Customer	Jun. 30, 2015 USD ($) Customer	Dec. 31, 2014 USD ($)
Offsetting Assets [Line Items]
Margin Deposit Assets | $	$ 1.1	$ 1.1	$ 0.8
Commodity Contract [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Amount Offset Against Collateral | $	$ 1.5	$ 1.5	$ 2.5
Customer Concentration Risk [Member] | Sales Revenue, Goods, Net [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage	35.00%	35.00%
Customer Concentration Risk [Member] | Cost of Goods, Total [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage		23.00%
Number of Suppliers	0
Customer Concentration Risk [Member] | Accounts Receivable [Member]
Offsetting Assets [Line Items]
Concentration Risk, Percentage		39.00%
Customer Concentration Risk [Member] | Crude [Member] | Sales Revenue, Goods, Net [Member]
Offsetting Assets [Line Items]
Number of Customers	2	2
Customer Concentration Risk [Member] | Crude [Member] | Cost of Goods, Total [Member]
Offsetting Assets [Line Items]
Purchases of product | $		$ 98.5
Number of Suppliers		2
Customer Concentration Risk [Member] | Crude [Member] | Accounts Receivable [Member]
Offsetting Assets [Line Items]
Number of Customers		1