Derivative and Hedging Instruments (Details-2) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commodity Derivative Contracts [Member]
Offsetting Assets [Line Items]
Gross amounts	$ 1,449	$ 676
Gross amounts offset in balance sheet	(287)	(654)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	1,162	22
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Gross amounts	478	329
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$ 478	$ 329

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

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