SEGMENTS OF BUSINESS (Details) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015 USD ($) investment	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) investment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Segment Reporting Information [Line Items]
Operating Revenues		$ 257,844	$ 141,062	$ 177,710	$ 382,952	$ 281,097	$ 122,427	$ 133,271	$ 350,201	$ 959,568	$ 886,996	$ 731,421
Operating Income (Loss)										156,894	127,603	69,636
Depreciation and Amortization										91,042	78,511	64,890
Interest Charges										31,622	29,560	18,825
Income Taxes		(1,006)	$ (10,968)	$ (3,279)	$ 16,613	10,415	$ (8,325)	$ (9,510)	$ 11,869	1,360	4,449	(19,014)
Property Additions										361,994	339,469	328,504
Identifiable Assets		$ 3,480,900				3,349,425				3,480,900	3,349,425
Marina Energy LLC [Member] | Energenic US LLC [Member]
Segment Reporting Information [Line Items]
Noncash or Part Noncash Acquisition, Fixed Assets Acquired										$ 40,900
Number of investments owned | investment		8								8
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Revenues										$ 1,006,642	926,518	772,551
Interest Charges										40,523	36,036	23,731
Operating Segments [Member] | Gas Utility Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										534,290	501,875	446,480
Operating Income (Loss)										119,585	113,690	105,822
Depreciation and Amortization										58,668	52,155	48,261
Interest Charges										19,906	17,872	12,550
Income Taxes										36,945	34,895	34,833
Property Additions										218,260	201,737	173,099
Identifiable Assets		$ 2,288,204				2,185,672				2,288,204	2,185,672
Operating Segments [Member] | Energy Group [Member]
Segment Reporting Information [Line Items]
Operating Revenues										366,345	327,822	237,511
Operating Income (Loss)										32,848	9,506	(37,540)
Depreciation and Amortization										596	251	299
Interest Charges										626	638	697
Income Taxes										13,858	5,419	(14,676)
Property Additions										2,435	1,439	752
Identifiable Assets		342,299				442,874				342,299	442,874
Operating Segments [Member] | Energy Group [Member] | Wholesale Energy Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										129,098	77,048	831
Operating Income (Loss)										35,024	9,493	(37,720)
Depreciation and Amortization										435	168	206
Interest Charges										441	371	417
Income Taxes										14,410	4,822	(15,070)
Property Additions										382	18	50
Identifiable Assets		231,660				366,119				231,660	366,119
Operating Segments [Member] | Energy Group [Member] | Retail Gas and Other Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										87,198	127,001	107,748
Operating Income (Loss)										(3,218)	479	278
Depreciation and Amortization										161	83	93
Interest Charges										185	267	280
Income Taxes										(978)	787	434
Property Additions										2,053	1,421	702
Identifiable Assets		55,111				53,073				55,111	53,073
Operating Segments [Member] | Energy Group [Member] | Retail Electric Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										150,049	123,773	128,932
Operating Income (Loss)										1,042	(466)	(98)
Income Taxes										426	(190)	(40)
Identifiable Assets		55,528				23,682				55,528	23,682
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues										74,851	66,647	57,274
Operating Income (Loss)										2,495	2,922	984
Depreciation and Amortization										30,558	25,289	15,453
Income Taxes										(49,039)	(36,181)	(39,518)
Property Additions										139,397	132,298	151,592
Identifiable Assets		796,121				679,042				796,121	679,042
Operating Segments [Member] | Energy Services [Member] | On-site Energy Production [Member]
Segment Reporting Information [Line Items]
Operating Revenues										63,665	56,129	43,551
Operating Income (Loss)										2,027	2,560	(2,011)
Depreciation and Amortization										30,242	25,020	15,192
Interest Charges										8,169	8,723	4,480
Income Taxes										(49,225)	(36,404)	(40,755)
Property Additions	[1]									139,018	132,214	151,592
Identifiable Assets		791,236				675,937				791,236	675,937
Operating Segments [Member] | Energy Services [Member] | Appliance Service Operations [Member]
Segment Reporting Information [Line Items]
Operating Revenues										11,186	10,518	13,723
Operating Income (Loss)										468	362	2,995
Depreciation and Amortization										316	269	261
Income Taxes										186	223	1,237
Property Additions										379	84	0
Identifiable Assets		4,885				3,105				4,885	3,105
Operating Segments [Member] | Corporate and Services [Member]
Segment Reporting Information [Line Items]
Operating Revenues										31,156	30,174	31,286
Operating Income (Loss)										1,966	1,485	370
Depreciation and Amortization										1,220	816	877
Interest Charges										11,822	8,803	6,004
Income Taxes										(404)	316	347
Property Additions										1,902	3,995	3,061
Identifiable Assets		653,659				527,691				653,659	527,691
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Identifiable Assets		1,545				1,758				1,545	1,758
Intersegment [Member]
Segment Reporting Information [Line Items]
Operating Revenues										(47,074)	(39,522)	(41,130)
Interest Charges										(8,901)	(6,476)	$ (4,906)
Identifiable Assets		$ (600,928)				$ (487,612)				$ (600,928)	$ (487,612)

[1] The property additions for On-Site Energy Production do not include the approximately $40.9 million of Property, Plant and Equipment obtained through the acquisition of eight Energenic projects as discussed in Note 3.