Note 5 - Derivative Instruments (Details) - Carrying Value of Derivative Instruments $ in Thousands |
Dec. 31, 2015
USD ($)
|
Dec. 31, 2014
USD ($)
|
|---|---|---|
| Commodity Option [Member] | ||
| Derivative [Line Items] | ||
| Regulated options, included in other current assets | (200) | (350) |
| Regulated options, included in other current assets | $ (427) | $ (794) |
| Future [Member] | ||
| Derivative [Line Items] | ||
| Regulated fixed price future commitments, included in other current assets | (631) | (225) |
| Regulated fixed price future commitments, included in other current assets | $ 3,789 | $ 862 |