REGULATORY ASSETS & REGULATORY LIABILITIES - ADDITIONAL DETAILS (Details) - USD ($) $ in Thousands	1 Months Ended
	Sep. 30, 2014	Dec. 31, 2015	Dec. 31, 2014
Regulatory Liabilities [Line Items]
Total regulatory liabilities		$ 42,841	$ 41,899
Excess Plant Removal Costs [Member]
Regulatory Liabilities [Line Items]
Total regulatory liabilities		32,644	35,940
Annual amortization reflected in depreciation expense	$ 1,100
Societal Benefit Costs Payable [Member]
Regulatory Liabilities [Line Items]
Total regulatory liabilities		10,197	1,025
Conservation Incentive Program - Payable [Member]
Regulatory Liabilities [Line Items]
Total regulatory liabilities		0	4,700
Other Regulatory Liabilities [Member]
Regulatory Liabilities [Line Items]
Total regulatory liabilities		$ 0	$ 234