SEGMENTS OF BUSINESS (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total Operating Revenues	$ 333,035	$ 382,952
Total Operating Income	114,253	76,371
Total Depreciation and Amortization	26,141	21,586
Total Interest Charges	9,160	8,601
Total Income Taxes	39,267	16,613
Total Property Additions	54,662	49,620
Total Identifiable Assets	3,493,984		$ 3,471,933
Operating Segments
Segment Reporting Information [Line Items]
Total Operating Revenues	349,149	395,873
Total Interest Charges	11,897	10,808
Operating Segments | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	134,298	103,200
Total Operating Income	38,070	3,235
Total Depreciation and Amortization	289	52
Total Interest Charges	196	315
Total Income Taxes	14,808	2,369
Total Property Additions	377	733
Total Identifiable Assets	285,743		342,299
Operating Segments | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	18,209	15,929
Total Operating Income	(45)	(534)
Total Depreciation and Amortization	10,003	7,125
Total Income Taxes	(2,986)	(12,055)
Total Property Additions	2,752	4,497
Total Identifiable Assets	788,323		795,116
Operating Segments | Gas Utility Operations
Segment Reporting Information [Line Items]
Total Operating Revenues	187,766	267,658
Total Operating Income	75,773	73,189
Total Depreciation and Amortization	15,626	14,167
Total Interest Charges	4,787	5,190
Total Income Taxes	27,404	26,172
Total Property Additions	51,370	43,326
Total Identifiable Assets	2,365,728		2,281,576
Operating Segments | Wholesale Energy Operations | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	65,074	35,345
Total Operating Income	38,244	330
Total Depreciation and Amortization	204	32
Total Interest Charges	64	242
Total Income Taxes	14,737	867
Total Property Additions	6	4
Total Identifiable Assets	174,326		231,660
Operating Segments | Retail Gas and Other Operations | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	29,733	38,078
Total Operating Income	(759)	3,087
Total Depreciation and Amortization	85	20
Total Interest Charges	132	73
Total Income Taxes	(168)	1,576
Total Property Additions	371	729
Total Identifiable Assets	60,178		55,111
Operating Segments | Retail Electric Operations | Energy Group
Segment Reporting Information [Line Items]
Total Operating Revenues	39,491	29,777
Total Operating Income	585	(182)
Total Income Taxes	239	(74)
Total Identifiable Assets	51,239		55,528
Operating Segments | On-Site Energy Production | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	16,321	13,572
Total Operating Income	(89)	(482)
Total Depreciation and Amortization	9,919	7,051
Total Interest Charges	3,462	2,315
Total Income Taxes	(3,012)	(12,047)
Total Property Additions	2,651	4,381
Total Identifiable Assets	784,474		790,231
Operating Segments | Appliance Service Operations | Energy Services
Segment Reporting Information [Line Items]
Total Operating Revenues	1,888	2,357
Total Operating Income	44	(52)
Total Depreciation and Amortization	84	74
Total Income Taxes	26	(8)
Total Property Additions	101	116
Total Identifiable Assets	3,849		4,885
Discontinued Operations
Segment Reporting Information [Line Items]
Total Identifiable Assets	1,542		1,545
Corporate and Services
Segment Reporting Information [Line Items]
Total Operating Revenues	8,876	9,086
Total Operating Income	455	481
Total Depreciation and Amortization	223	242
Total Interest Charges	3,452	2,988
Total Income Taxes	41	127
Total Property Additions	163	1,064
Total Identifiable Assets	648,213		652,325
Intersegment Elimination
Segment Reporting Information [Line Items]
Total Operating Revenues	(16,114)	(12,921)
Total Interest Charges	(2,737)	$ (2,207)
Total Identifiable Assets	$ (595,565)		$ (600,928)