Derivative and Hedging Instruments (Details-2) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Commodity Derivative Contracts [Member]
Offsetting Assets [Line Items]
Gross amounts	$ 1,957	$ 290
Gross amounts offset in balance sheet	(272)	(290)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	1,685	0
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Gross amounts	34	234
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$ 34	$ 234

Amount of obligation to return cash collateral under master netting arrangements offset against derivative assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
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-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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