BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Segment Reporting Information [Line Items]
Utility		$ 116,307	$ 111,383	$ 699,737	$ 739,380
Nonutility		342,160	576,874	1,595,944	2,406,851
Total operating revenues		458,467	688,257	2,295,681	3,146,231
Depreciation and amortization		15,574	13,620	45,164	39,014
Interest income	[1]	(25)	278	311	790
Interest expense, net of capitalized interest		7,327	6,507	21,005	19,108
Income tax (benefit) provision		(4,318)	(7,808)	56,693	65,377
Equity in earnings of affiliates		3,367	2,681	9,749	8,056
Net financial earnings (loss)		2,477	4,514	156,729	196,295
Capital expenditures		68,996	84,511	227,418	201,276
Investments in equity investees		1,049	0	$ 2,313	$ 0
Canada [Member]
Segment Reporting Information [Line Items]
Percentage to total operating revenues				3.60%	3.60%
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Investments in equity investees		1,049	0	$ 2,313	$ 0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues		445,943	675,171	2,325,568	3,187,313
Depreciation and amortization		15,338	13,406	44,466	38,387
Interest income	[1]	471	518	1,087	1,498
Interest expense, net of capitalized interest		7,455	6,421	21,191	18,780
Income tax (benefit) provision		(4,890)	(9,301)	57,402	64,816
Net financial earnings (loss)		597	2,015	156,871	195,587
Capital expenditures		68,967	84,352	227,328	200,640
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		10,810	10,567	32,002	30,374
Interest income	[1]	(25)	137	75	579
Interest expense, net of capitalized interest		5,005	4,540	14,002	12,412
Income tax (benefit) provision		3,754	4,348	41,698	42,256
Net financial earnings (loss)		7,172	4,882	83,952	79,564
Capital expenditures		45,749	38,186	115,740	109,071
Operating Segments [Member] | Natural Gas Distribution [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Utility		116,307	111,383	699,737	739,380
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		23	15	68	40
Interest income	[1]	250	210	263	210
Interest expense, net of capitalized interest		209	166	1,010	1,443
Income tax (benefit) provision		(9,958)	(16,256)	39,842	36,816
Net financial earnings (loss)		(5,270)	(8,628)	47,482	90,153
Operating Segments [Member] | Energy Services [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	[2]	320,221	560,115	1,546,890	2,367,641
Operating Segments [Member] | Energy Services [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility		1,554	518	60,777	72,285
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		4,504	2,823	12,392	7,969
Interest income	[1]	0	0	22	0
Interest expense, net of capitalized interest		2,078	1,382	5,556	3,817
Income tax (benefit) provision		(423)	1,286	(29,186)	(18,146)
Net financial earnings (loss)		(3,792)	3,865	18,226	20,286
Capital expenditures		23,218	46,166	111,588	91,569
Operating Segments [Member] | Clean Energy Ventures [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility		7,861	3,155	18,164	8,007
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		1	1	4	4
Interest income	[1]	246	171	727	709
Interest expense, net of capitalized interest		163	333	623	1,108
Income tax (benefit) provision		1,737	1,321	5,048	3,890
Equity in earnings of affiliates		4,266	3,511	12,622	10,594
Net financial earnings (loss)		2,487	1,896	7,211	5,584
Home Services and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		238	212	714	627
Interest income	[1]	13	1	214	1
Interest expense, net of capitalized interest		134	86	76	328
Income tax (benefit) provision		720	1,680	(704)	360
Net financial earnings (loss)		1,909	2,485	(42)	708
Capital expenditures		29	159	90	636
Home Services and Other [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility		14,078	13,604	30,890	31,203
Home Services and Other [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility		514	194	1,300	693
Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility		(2,068)	(712)	(62,077)	(72,978)
Depreciation and amortization		(2)	2	(16)	0
Interest income	[1]	(509)	(241)	(990)	(709)
Interest expense, net of capitalized interest		(262)	0	(262)	0
Income tax (benefit) provision		(148)	(187)	(5)	201
Equity in earnings of affiliates		(899)	(830)	(2,873)	(2,538)
Net financial earnings (loss)		$ (29)	$ 14	$ (100)	$ 0

[1] Included in other income, net on the Unaudited Condensed Consolidated Statements of Operations.

[2] Includes sales to Canada, which accounted for 3.6 percent of total operating revenues during the nine months ended June 30, 2015 and 2014.