SEGMENTS OF BUSINESS (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) category	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 244,374	$ 154,402	$ 670,203	$ 487,437
Total Operating (Loss) Income	(4,564)	(7,986)	63,122	106,267
Total Depreciation and Amortization	29,711	27,321	59,232	53,462
Total Interest Charges	10,979	8,229	27,724	17,389
Total Income Taxes	(5,544)	(7,189)	16,326	32,078
Total Property Additions	70,275	53,968	140,453	108,630
Total Identifiable Assets	3,741,860		3,741,860		$ 3,730,567
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	1,778		$ 1,778		1,756
Energy Group and Energy Services
Segment Reporting Information [Line Items]
Number of operating categories | category			2
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	262,167	166,333	$ 705,199	515,482
Total Interest Charges	15,093	10,931	35,170	22,828
Operating Segments | Gas Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	83,251	68,762	280,065	256,528
Total Operating (Loss) Income	8,156	9,931	88,802	85,704
Total Depreciation and Amortization	17,446	15,788	34,808	31,414
Total Interest Charges	6,077	4,552	11,955	9,339
Total Income Taxes	1,431	1,415	31,342	28,819
Total Property Additions	66,128	50,133	128,408	101,503
Total Identifiable Assets	2,673,743		2,673,743		2,551,923
Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	140,788	64,061	354,140	198,359
Total Operating (Loss) Income	(18,596)	(22,622)	(30,583)	15,448
Total Depreciation and Amortization	117	287	228	576
Total Interest Charges	198	79	3,342	275
Total Income Taxes	(6,505)	(8,877)	(12,736)	5,931
Total Property Additions	137	355	435	732
Total Identifiable Assets	237,366		237,366		327,028
Operating Segments | Energy Group | Wholesale Energy Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	76,409	(1,309)	203,926	63,765
Total Operating (Loss) Income	(18,191)	(31,149)	(29,817)	7,095
Total Depreciation and Amortization	33	204	61	408
Total Interest Charges	134	1	3,193	65
Total Income Taxes	(6,384)	(12,258)	(12,703)	2,479
Total Property Additions	4	1	7	7
Total Identifiable Assets	165,932		165,932		233,019
Operating Segments | Energy Group | Retail Gas and Other Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	21,759	22,305	58,637	52,038
Total Operating (Loss) Income	(1,560)	6,250	(3,227)	5,491
Total Depreciation and Amortization	84	83	167	168
Total Interest Charges	64	78	149	210
Total Income Taxes	(593)	2,450	(1,040)	2,282
Total Property Additions	133	354	428	725
Total Identifiable Assets	36,954		36,954		52,729
Operating Segments | Energy Group | Retail Electric Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	42,620	43,065	91,577	82,556
Total Operating (Loss) Income	1,155	2,277	2,461	2,862
Total Income Taxes	472	931	1,007	1,170
Total Identifiable Assets	34,480		34,480		41,280
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	27,115	25,093	48,385	43,302
Total Operating (Loss) Income	5,170	4,819	3,129	4,774
Total Depreciation and Amortization	11,730	10,986	23,377	20,989
Total Income Taxes	255	236	(2,831)	(2,750)
Total Property Additions	3,171	2,916	10,526	5,668
Total Identifiable Assets	722,127		722,127		770,589
Operating Segments | Energy Services | On-Site Energy Production
Segment Reporting Information [Line Items]
Total Operating Revenues	25,135	23,043	44,747	39,364
Total Operating (Loss) Income	5,104	4,561	3,135	4,472
Total Depreciation and Amortization	11,674	10,895	23,267	20,814
Total Interest Charges	3,877	3,442	9,691	6,904
Total Income Taxes	219	110	(2,850)	(2,902)
Total Property Additions	2,917	2,665	10,266	5,316
Total Identifiable Assets	719,556		719,556		767,710
Operating Segments | Energy Services | Appliance Service Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	1,980	2,050	3,638	3,938
Total Operating (Loss) Income	66	258	(6)	302
Total Depreciation and Amortization	56	91	110	175
Total Income Taxes	36	126	19	152
Total Property Additions	254	251	260	352
Total Identifiable Assets	2,571		2,571		2,879
Corporate and Services
Segment Reporting Information [Line Items]
Total Operating Revenues	11,013	8,417	22,609	17,293
Total Operating (Loss) Income	706	(114)	1,774	341
Total Depreciation and Amortization	418	260	819	483
Total Interest Charges	4,941	2,858	10,182	6,310
Total Income Taxes	(725)	37	551	78
Total Property Additions	839	564	1,084	727
Total Identifiable Assets	708,131		708,131		649,795
Intersegment eliminations
Segment Reporting Information [Line Items]
Total Operating Revenues	(17,793)	(11,931)	(34,996)	(28,045)
Total Interest Charges	(4,114)	$ (2,702)	(7,446)	$ (5,439)
Total Identifiable Assets	$ (601,285)		$ (601,285)		$ (570,524)