Derivative Instruments (Impact of Derivative Instruments Not Designated as Fair Value Hedges) (Details) - Not Designated as Hedging Instrument [Member] - Commodity Forward Contracts [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	$ 5,370		$ 12,838
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	6,163		5,073
Cost of Sales [Member]
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	(9,167)	$ 4,057
Accounts receivable, net [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	3,124		7,589
Deferred Charges and other assets, net [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset Including Not Subject to Master Netting Arrangement	2,246		5,249
Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	1,048		1,349
Other Liabilities [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	$ 5,115		$ 3,724