SEGMENTS OF BUSINESS (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Operating Revenues	$ 382,952us-gaap_Revenues	$ 350,201us-gaap_Revenues
Operating Income (Loss)	76,371us-gaap_OperatingIncomeLoss	62,510us-gaap_OperatingIncomeLoss
Depreciation and Amortization	21,586us-gaap_DepreciationAndAmortization	18,799us-gaap_DepreciationAndAmortization
Interest Charges	8,601us-gaap_InterestExpense	7,084us-gaap_InterestExpense
Income Taxes	16,613us-gaap_IncomeTaxExpenseBenefit	11,869us-gaap_IncomeTaxExpenseBenefit
Property Additions	49,620	42,628
Identifiable Assets	3,376,722us-gaap_Assets		3,349,425us-gaap_Assets
Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	395,873	359,687
Interest Charges	10,808	8,567
Operating Segments \| Gas Utility Operations
Segment Reporting Information [Line Items]
Operating Revenues	267,658	210,545
Operating Income (Loss)	73,189	63,440
Depreciation and Amortization	14,167	12,676
Interest Charges	5,190	4,342
Income Taxes	26,172	22,527
Property Additions	43,326	32,531
Identifiable Assets	2,291,920		2,185,672
Operating Segments \| Energy Group
Segment Reporting Information [Line Items]
Operating Revenues	103,200	127,271
Operating Income (Loss)	3,235	259
Depreciation and Amortization	52	62
Interest Charges	315	247
Income Taxes	2,369	361
Property Additions	733	170
Identifiable Assets	371,990		442,874
Operating Segments \| Energy Group \| Wholesale Energy Operations
Segment Reporting Information [Line Items]
Operating Revenues	35,345	35,372
Operating Income (Loss)	330	(1,655)
Depreciation and Amortization	32	40
Interest Charges	242	121
Income Taxes	867	(553)
Property Additions	4	2
Identifiable Assets	294,484		366,119
Operating Segments \| Energy Group \| Retail Gas and Other Operations
Segment Reporting Information [Line Items]
Operating Revenues	38,078	51,506
Operating Income (Loss)	3,087	1,968
Depreciation and Amortization	20	22
Interest Charges	73	126
Income Taxes	1,576	936
Property Additions	729	168
Identifiable Assets	52,195		53,073
Operating Segments \| Energy Group \| Retail Electric Operations
Segment Reporting Information [Line Items]
Operating Revenues	29,777	40,393
Operating Income (Loss)	(182)	(54)
Income Taxes	(74)	(22)
Identifiable Assets	25,311		23,682
Operating Segments \| Energy Services
Segment Reporting Information [Line Items]
Operating Revenues	15,929	14,000
Operating Income (Loss)	(534)	(1,355)
Depreciation and Amortization	7,125	5,842
Income Taxes	(12,055)	(11,048)
Property Additions	4,497	9,149
Identifiable Assets	664,750		679,042
Operating Segments \| Energy Services \| On-site Energy Production
Segment Reporting Information [Line Items]
Operating Revenues	13,572	11,346
Operating Income (Loss)	(482)	(1,260)
Depreciation and Amortization	7,051	5,775
Interest Charges	2,315	2,128
Income Taxes	(12,047)	(11,025)
Property Additions	4,381	9,149
Identifiable Assets	661,485		675,937
Operating Segments \| Energy Services \| Appliance Service Operations
Segment Reporting Information [Line Items]
Operating Revenues	2,357	2,654
Operating Income (Loss)	(52)	(95)
Depreciation and Amortization	74	67
Income Taxes	(8)	(23)
Property Additions	116	0
Identifiable Assets	3,265		3,105
Operating Segments \| Corporate and Services
Segment Reporting Information [Line Items]
Operating Revenues	9,086	7,871
Operating Income (Loss)	481	166
Depreciation and Amortization	242	219
Interest Charges	2,988	1,850
Income Taxes	127	29
Property Additions	1,064	778
Identifiable Assets	563,649		527,691
Discontinued Operations
Segment Reporting Information [Line Items]
Identifiable Assets	1,755		1,758
Intersegment Elimination
Segment Reporting Information [Line Items]
Operating Revenues	(12,921)	(9,486)
Interest Charges	(2,207)	(1,483)
Identifiable Assets	$ (517,342)		$ (487,612)

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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