Note 5 - Fair Value of Financial Instruments (Details Textual) BTU in Millions, $ in Millions				1 Months Ended	3 Months Ended			7 Months Ended	8 Months Ended	9 Months Ended
	Feb. 24, 2016 Boe BTU $ / item	Mar. 14, 2015 $ / BTU	Mar. 06, 2014 BTU $ / BTU	Mar. 31, 2016 Boe $ / item	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2015 BTU	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Feb. 28, 2016 $ / item
NGI Swap Contract [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU			2.2				2.4
Underlying, Derivative Energy Measure | $ / BTU		3	4.95
Henry Hub Natural Gas Future ("NG") Contracts [Member] | Call Option [Member]
Proceeds from Derivative Instrument, Investing Activities | $									$ 1.9
Henry Hub Natural Gas Future ("NG") Contracts [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | BTU	4.1
Derivative, Price Risk Option Strike Price	2
Brent Oil Future Contracts [Member] | Call Option [Member]
Proceeds from Derivative Instrument, Investing Activities | $								$ 1.1
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]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe	185,000
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
Rolled Two Existing Options [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe				31,800
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] | 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 1 [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe				16,500
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
Short Risk Reversal Transactions, Rolling Existing Call Option 2 [Member]
Derivative, Nonmonetary Notional Amount, Energy Measure | Boe				17,000
Foreign Currency Gain (Loss) [Member]
Gain (Loss) on Price Risk Derivative Instruments Not Designated as Hedging Instruments | $						$ (0.9)					$ (1.3)
Electricity Revenues [Member]
Gain (Loss) on Price Risk Derivative Instruments Not Designated as Hedging Instruments | $						$ 0.4					$ 0.8
Derivative, Number of Options Rolled				2
Gain (Loss) on Price Risk Derivative Instruments Not Designated as Hedging Instruments | $					$ (1.0)					$ (1.3)