Derivative and Hedging Instruments (Details-2) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commodity Derivative Contracts [Member]
Offsetting Assets [Line Items]
Gross amounts	$ 675	$ 801
Gross amounts offset in balance sheet	(212)	(342)
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	463	459
Financial Transmission Rights [Member]
Offsetting Assets [Line Items]
Gross amounts	124	241
Gross amounts offset in balance sheet	0	0
Collateral posted against derivative positions	0	0
Net amount presented in balance sheet	$ 124	$ 241

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

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