4. Derivatives - Schedule of Derivatives Not Designated as Hedging Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Commodity contracts - Derivative assets	$ 3,242	$ 2,081
Commodity contracts - Derivative liabilities	3,294	1,848
Commodity Contracts [Member] \| Non Designated Derivative Instruments [Member]
Commodity contracts - Derivative assets	3,242	2,081
Commodity contracts - Derivative liabilities	$ 3,492	$ 1,848

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=64837297&loc=SL5624163-113959

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant