Risk Management and Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair value of derivative financial instruments
Current assets	$ 608	$ 1,295
Total derivatives assets	608	1,311
Current liabilities	4,743	4,472
Non-current liabilities and deferred credits	3,873	3,696
Total derivatives liabilities	8,616	8,168
Hedging instruments \| Commodity contracts \| Gas
Fair value of derivative financial instruments
Current assets	18	2
Non-current other assets		16
Current liabilities	14	282
Non-current liabilities and deferred credits	51	66
Hedging instruments \| Commodity contracts \| Electric
Fair value of derivative financial instruments
Current liabilities	4,729	4,190
Non-current liabilities and deferred credits	3,822	3,630
Hedging instruments \| Transmission congestion rights (TCR) \| Electric
Fair value of derivative financial instruments
Current assets	$ 590	$ 1,293

Fair value, before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

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