REGULATORY ASSETS AND LIABILITIES - REGULATORY LIABILITIES (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 51,050	$ 42,841
Excess Plant Removal Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	30,324	32,644
Deferred Revenues-Net
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	14,418	0
Societal Benefit Costs
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	5,907	10,197
Energy Efficiency Tracker
Regulatory Liabilities [Line Items]
Total Regulatory Liabilities	$ 401	$ 0