Physical Delivery Contracts and Commodity Derivatives (Details 3) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Commodity derivative assets:
Current derivative assets		$ 408
Total derivative assets		559
Commodity derivative liabilities:
Current derivative liabilities	264
Total derivative liabilities	264
Gross Recognized Assets/Liabilities [Member]
Commodity derivative assets:
Current derivative assets	41
Total derivative assets	41
Commodity derivative liabilities:
Current derivative liabilities	305
Total derivative liabilities	305
Gross Amounts Offset [Member]
Commodity derivative assets:
Current derivative assets	(41)
Total derivative assets	(41)
Commodity derivative liabilities:
Current derivative liabilities	(41)
Total derivative liabilities	(41)
Net Recognized Fair Value Assets/Liabilities [Member]
Commodity derivative assets:
Current derivative assets
Total derivative assets
Commodity derivative liabilities:
Current derivative liabilities	264
Total derivative liabilities	$ 264