REGULATED OPERATING EXPENSE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
REGULATED OPERATING EXPENSE
Electric transmission and distribution expense	$ 28,893	$ 27,919	$ 21,863
Natural gas transmission and distribution expense	2,699	2,362	2,498
Power operation expense (other than fuel)	18,263	16,089	15,643
Customer accounts and assistance expense	10,937	11,239	11,180
Employee pension expense	10,786	10,590	10,736
Employee healthcare expense	10,162	9,147	10,190
General office supplies and expense	14,438	15,024	12,850
Administrative and general expense	14,863	14,385	14,800
Allowance for uncollectible accounts	2,080	3,420	3,665
Regulatory reversal of gain on sale of assets		44	1,236
Miscellaneous expense	430	472	672
Total	$ 113,551	$ 110,691	$ 105,333