SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Municipal Franchise Taxes
Municipal franchise taxes	$ 11,400	$ 11,800	$ 11,200
Property, Plant and Equipment
Period for refund of pro rata amount of the original cost of the extension to developers	5 years
Liability for refund of pro rata amount of the original cost of the extension to developers	$ 2,100	1,900
Regulatory Liability [Abstract]
Regulatory liability	141,072	136,369
Electric | Costs of removal
Regulatory Liability [Abstract]
Regulatory liability	85,400	82,800
Gas | Costs of removal
Regulatory Liability [Abstract]
Regulatory liability	$ 8,800	$ 7,700