Derivative Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Fair Values of Derivatives Instruments in Consolidated Balance Sheets

The fair values of derivative instruments reflected in the Company's consolidated balance sheets were as follows:

	Asset Derivatives
	Balance Sheet Location	Fair Value as of
		March 31, 2017		December 31, 2016
Not designated as hedging instruments
Commodity forward contracts	Accounts receivable, net	$	3,124	$	7,589
Commodity forward contracts	Deferred charges and other    assets, net	2,246		5,249
Total asset derivatives		$	5,370	$	12,838

	Liability Derivatives
	Balance Sheet Location	Fair Value as of
		March 31, 2017		December 31, 2016
Not designated as hedging instruments
Commodity forward contracts	Accrued liabilities	$	1,048	$	1,349
Commodity forward contracts	Other liabilities	5,115		3,724
Total liability derivatives		$	6,163	$	5,073

Impact of Derivative Instruments Not Designated as Fair Value Hedges

The impact of derivative instruments that have not been designated as hedges on the Company's consolidated statements of operations were as follows:

Derivatives Not Designated as    Hedging Instruments	Location of Gain (Loss) Recognized  in Income on Derivative	Three Months Ended March 31,
		2017			2016
Commodity forward contracts	Cost of sales	$	(9,167	)	$	4,057

ImpactofDerivativesNetInConsolidatedBalanceSheet [Table Text Block]

	March 31, 2017
	Net Presentation			Gross Presentation
	Net Assets (Liabilities) Presented in the Consolidated Balance Sheets			Risk management assets—Commodity forward contracts		Risk management liabilities—Commodity forward contracts
Accounts receivable, net
Derivative positions subject to enforceable master netting    arrangements	$	520		$	1,049	$	(529	)
Derivative positions not subject to enforceable master netting    arrangements	2,604			2,604		—
	3,124			3,653		(529		)
Deferred charges and other assets, net
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	2,246			2,246		—
	2,246			2,246		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(1,048		)	—		(1,048		)
	(1,048		)	—		(1,048		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(1,629		)	978		(2,607		)
Derivative positions not subject to enforceable master netting arrangements	(3,486		)	—		(3,486		)
	(5,115		)	978		(6,093		)
Risk management assets (liabilities)—Commodity forward    contracts				$	6,877	$	(7,670	)

	December 31, 2016
	Net Presentation			Gross Presentation
	Net Assets (Liabilities) Presented in the Consolidated Balance Sheets			Risk management assets—Commodity forward contracts		Risk management liabilities—Commodity forward contracts
Accounts receivable, net
Derivative positions subject to enforceable master netting arrangements	$	1,498		$	1,636	$	(138	)
Derivative positions not subject to enforceable master netting arrangements	6,091			6,091		—
	7,589			7,727		(138		)
Deferred charges and other assets, net
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	5,249			5,249		—
	5,249			5,249		—
Accrued liabilities
Derivative positions subject to enforceable master netting arrangements	—			—		—
Derivative positions not subject to enforceable master netting arrangements	(1,349		)	—		(1,349		)
	(1,349		)	—		(1,349		)
Other liabilities
Derivative positions subject to enforceable master netting arrangements	(436		)	2,010		(2,446		)
Derivative positions not subject to enforceable master netting arrangements	(3,288		)	—		(3,288		)
	(3,724		)	2,010		(5,734		)
Risk management assets (liabilities)—Commodity forward    contracts				$	14,986	$	(7,221	)