BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Segment Reporting Information [Line Items]
Utility		$ 119,206	$ 116,307	$ 513,348	$ 699,737
Nonutility		274,007	342,160	898,316	1,595,944
Total operating revenues		393,213	458,467	1,411,664	2,295,681
Depreciation and amortization		18,671	15,574	52,897	45,164
Interest income	[1]	65	(25)	188	311
Interest expense, net of capitalized interest		7,787	7,327	21,933	21,005
Income tax provision (benefit)		(14,190)	(4,318)	10,347	56,693
Equity in earnings of affiliates		2,257	3,367	7,065	9,749
Net financial earnings (loss)		10,972	2,477	140,144	156,729
Capital expenditures		81,938	68,996	250,295	227,418
Investments in equity investees		2,741	1,049	$ 8,689	$ 2,313
Canada [Member]
Segment Reporting Information [Line Items]
Percentage to total operating revenues				2.40%	3.60%
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues		382,216	445,943	$ 1,390,465	$ 2,325,568
Depreciation and amortization		18,391	15,338	52,262	44,466
Interest income	[1]	473	471	1,387	1,087
Interest expense, net of capitalized interest		7,920	7,455	22,351	21,191
Income tax provision (benefit)		(15,946)	(4,890)	10,502	57,402
Net financial earnings (loss)		8,661	597	139,887	156,871
Capital expenditures		81,541	68,967	248,829	227,328
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		12,297	10,810	35,133	32,002
Interest income	[1]	62	(25)	190	75
Interest expense, net of capitalized interest		4,935	5,005	14,213	14,002
Income tax provision (benefit)		2,015	3,754	38,232	41,698
Net financial earnings (loss)		3,607	7,172	83,494	83,952
Capital expenditures		36,687	45,749	133,093	115,740
Operating Segments [Member] | Natural Gas Distribution [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Utility		119,206	116,307	513,348	699,737
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		23	23	69	68
Interest income	[1]	16	250	88	263
Interest expense, net of capitalized interest		263	209	639	1,010
Income tax provision (benefit)		(16,678)	(9,958)	(3,968)	39,842
Net financial earnings (loss)		276	(5,270)	27,585	47,482
Operating Segments [Member] | Energy Services [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	[2]	247,633	320,221	840,518	1,546,890
Operating Segments [Member] | Energy Services [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility		2,674	1,554	8,440	60,777
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		6,070	4,504	17,056	12,392
Interest income	[1]	0	0	0	22
Interest expense, net of capitalized interest		2,666	2,078	7,271	5,556
Income tax provision (benefit)		(2,784)	(423)	(28,433)	(29,186)
Net financial earnings (loss)		2,440	(3,792)	21,898	18,226
Capital expenditures		44,854	23,218	115,736	111,588
Operating Segments [Member] | Clean Energy Ventures [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility		12,703	7,861	28,159	18,164
Operating Segments [Member] | Midstream [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		1	1	4	4
Interest income	[1]	395	246	1,109	727
Interest expense, net of capitalized interest		56	163	228	623
Income tax provision (benefit)		1,501	1,737	4,671	5,048
Equity in earnings of affiliates		3,359	4,266	10,412	12,622
Net financial earnings (loss)		2,338	2,487	6,910	7,211
Investments in equity investees		2,741	1,049	8,689	2,313
Home Services and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization		249	238	713	714
Interest income	[1]	97	13	257	214
Interest expense, net of capitalized interest		65	134	170	76
Income tax provision (benefit)		1,556	720	(1,055)	(704)
Net financial earnings (loss)		2,418	1,909	662	(42)
Capital expenditures		397	29	1,466	90
Home Services and Other [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility		13,671	14,078	29,639	30,890
Home Services and Other [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility		737	514	2,273	1,300
Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility		(3,411)	(2,068)	(10,713)	(62,077)
Depreciation and amortization		31	(2)	(78)	(16)
Interest income	[1]	(505)	(509)	(1,456)	(990)
Interest expense, net of capitalized interest		(198)	(262)	(588)	(262)
Income tax provision (benefit)		200	(148)	900	(5)
Equity in earnings of affiliates		(1,102)	(899)	(3,347)	(2,873)
Net financial earnings (loss)		$ (107)	$ (29)	$ (405)	$ (100)

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

[2] Includes sales to Canada, which accounted for 2.4 and 3.6 percent of total operating revenues during the nine months ended June 30, 2016 and 2015.