4. Derivatives (Tables)

9 Months Ended

Sep. 30, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivatives Not Designated as Hedging Instruments

	As of September 30, 2016
	Assets			Liabilities
Type of Instrument	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Commodity contracts	Derivative instruments	$	3,242	Derivative instruments	$	3,492
		$	3,242		$	3,492

	As of December 31, 2015
	Assets			Liabilities
Type of Instrument	Balance Sheet Location	Fair Value		Balance Sheet Location	Fair Value
Commodity contracts	Derivative instruments	$	2,081	Derivative instruments	$	1,848
		$	2,081		$	1,848

Schedule of Recognized Gains (Losses) for Derivatives

		Realized Gains (Losses)
		Three Months Ended September 30,
Type of Instrument	Statements of Operations Location	2016			2015
Commodity contracts	Cost of goods sold	$	2,242		$	(251	)
		$	2,242		$	(251	)
		Unrealized Losses
		Three Months Ended September 30,
Type of Instrument	Statements of Operations Location	2016			2015
Commodity contracts	Cost of goods sold	$	(1,383	)	$	(824	)
		$	(1,383	)	$	(824	)
		Realized Gains (Losses)
			Nine Months Ended September 30,
Type of Instrument	Statements of Operations Location	2016			2015
Commodity contracts	Cost of goods sold	$	2,152		$	(101	)
		$	2,152		$	(101	)
		Unrealized Losses
			Nine Months Ended September 30,
Type of Instrument	Statements of Operations Location	2016			2015
Commodity contracts	Cost of goods sold	$	(483	)	$	(1,451	)
		$	(483	)	$	(1,451	)