Note 8 - Fair Value of Financial Instruments (Details Textual) BTU in Millions, $ in Millions							1 Months Ended	3 Months Ended	10 Months Ended	11 Months Ended	12 Months Ended
	Feb. 24, 2016 Boe $ / item	Feb. 02, 2016 BTU $ / item	Mar. 14, 2015 $ / BTU	Mar. 06, 2014 BTU $ / BTU	Oct. 16, 2013 MWh BTU £ / item bbl	Sep. 03, 2013 BTU £ / item	Mar. 31, 2016 Boe $ / item	Mar. 31, 2015 BTU	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Feb. 28, 2016 $ / item
Derivative, Number of Options Rolled							2
Gain (Loss) on Price Risk Derivative Instruments Not Designated as Hedging Instruments | $											$ (2.4)	$ (1.2)	$ (4.9)
Foreign Currency Gain (Loss) [Member]
Gain (Loss) on Price Risk Derivative Instruments Not Designated as Hedging Instruments | $												$ 1.2	$ 5.7
NGI Swap Contract [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU				2.2	4.2	4.4		2.4
Underlying, Derivative Energy Measure			3,000,000	4,950,000	4,103,000	4,035,000
New York Harbor ULSD Swap Contract [Member]
Underlying, Derivative Energy Measure | £ / item					125.15
Derivative, Nonmonetary Notional Amount, Volume | bbl					275,000
Fluctuation in Energy Rate | MWh					25
Henry Hub Natural Gas Future ("NG") Contracts [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU		4.1
Derivative, Price Risk Option Strike Price		2
Henry Hub Natural Gas Future ("NG") Contracts [Member] | Call Option [Member]
Proceeds from Derivative Instrument, Investing Activities | $										$ 1.9
Brent Oil Future Contracts [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe	185,000
Brent Oil Future Contracts [Member] | Minimum [Member]
Derivative, Price Risk Option Strike Price	32.8
Brent Oil Future Contracts [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price	35.5
Brent Oil Future Contracts [Member] | Call Option [Member]
Proceeds from Derivative Instrument, Investing Activities | $									$ 1.1
Rolled Two Existing Options [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe							31,800
Rolled Two Existing Options [Member] | Minimum [Member]
Derivative, Price Risk Option Strike Price							41
Rolled Two Existing Options [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price							42.5
Before Rolling Two Existing Options [Member] | Minimum [Member]
Derivative, Price Risk Option Strike Price														32.8
Before Rolling Two Existing Options [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price														33.5
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe							16,500
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member] | Minimum [Member]
Derivative, Price Risk Option Strike Price							28.5
Short Risk Reversal Transactions, Rolling Existing Call Option 1 [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price							37.5
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member] | Minimum [Member]
Derivative, Price Risk Option Strike Price							28
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member] | Maximum [Member]
Derivative, Price Risk Option Strike Price							38.5