Note 3 - Rate and Regulatory Matters - Summary of Interim Rate Information (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Apr. 14, 2016	Feb. 16, 2016
Revenue Increase – Annualized based on Test Year Data, initial request			$ 19,296
Revenue Increase – Annualized based on Test Year Data, interim rate		$ 16,816
Revenue Increase – Annualized based on Test Year Data, projected final rates	$ 12,100
Revenue Percent Increase, initial request			9.80%
Revenue Percent Increase, interim rate		9.56%
Revenue Percent Increase, projected final rates	6.23%
Return on Rate Base, initial request			8.07%
Return on Rate Base, interim rate		8.07%
Return on Rate Base, projected final rates	7.5056%
Jurisdictional Rate Base based on Test Year Data, initial request			$ 483,000
Jurisdictional Rate Base based on Test Year Data, interim rate		$ 483,000
Jurisdictional Rate Base based on Test Year Data, projected final rates	$ 471,000
Return on Equity, initial request			10.40%
Return on Equity, interim rate		10.10%
Return on Equity, projected final rates	9.41%
Based on Equity to Total Capital of, initial request			52.50%
Based on Equity to Total Capital of, interim rate		52.50%
Based on Equity to Total Capital of, projected final rates	52.50%
Debt to Total Capital, initial request			47.50%
Debt to Total Capital, interim rate		47.50%
Debt to Total Capital, projected final rates	47.50%