Physical Delivery Contracts and Gas Derivatives (Details 4) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Commodity derivative assets:
Current assets		$ 408
Non-current assets		151
Total derivative assets		559
Commodity derivative liabilities:
Current liability	306
Non-current liabilities	102
Total derivative liabilities	408
Gross Recognized Assets/Liabilities [Member]
Commodity derivative assets:
Current assets	82
Non-current assets	58
Total derivative assets	140
Commodity derivative liabilities:
Current liability	388
Non-current liabilities	160
Total derivative liabilities	548
Gross Amounts Offset [Member]
Commodity derivative assets:
Current assets	(82)
Non-current assets	(58)
Total derivative assets	(140)
Commodity derivative liabilities:
Current liability	(82)
Non-current liabilities	(58)
Total derivative liabilities	(140)
Net Recognized Fair Value Assets/Liabilities [Member]
Commodity derivative assets:
Current assets
Total derivative assets
Commodity derivative liabilities:
Current liability	306
Non-current liabilities	102
Total derivative liabilities	$ 408