BUSINESS SEGMENT AND OTHER OPERATIONS DATA, RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) (USD $) In Thousands	3 Months Ended				9 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010
Segment Reporting Information [Line Items]
Utility	$ 138,149		$ 105,130		$ 862,073		$ 794,311
Nonutility	510,020		374,764		1,476,235		1,213,475
Total operating revenues	648,169		479,894		2,338,308		2,007,786
Depreciation and amortization	8,514		8,136		25,445		23,936
Investment Income, Interest	311	[1]	622	[1]	874	[1]	1,538	[1]
Interest expense, net of capitalized interest	4,744		5,238		15,085		15,946
Income tax provision (benefit)	6,197		(10,555)		48,662		68,066
Equity in earnings of affiliates	2,957		1,981		9,484		7,885
Net Financial Earnings (Loss)	9,699		11,587		105,858		103,011
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	38,835		24,145		97,921		56,408
Payments to Acquire Equity Method Investments	0		0		0		4,300
Reportable Segment [Member]
Segment Reporting Information [Line Items]
Total operating revenues	638,890		469,930		2,366,663		2,009,524
Depreciation and amortization	8,323		7,977		24,843		23,461
Investment Income, Interest	530	[1]	842	[1]	1,530	[1]	2,177	[1]
Interest expense, net of capitalized interest	4,640		4,944		14,695		15,499
Income tax provision (benefit)	5,615		(10,062)		49,137		69,905
Equity in earnings of affiliates	3,891		2,538		11,871		10,261
Net Financial Earnings (Loss)	8,298		11,273		104,945		104,652
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	37,823		23,778		94,946		55,948
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	8,192		7,939		24,650		23,321
Investment Income, Interest	304	[1]	608	[1]	844	[1]	1,508	[1]
Interest expense, net of capitalized interest	3,630		4,139		11,454		12,545
Income tax provision (benefit)	3,283		2,081		44,162		41,326
Net Financial Earnings (Loss)	5,979		6,109		74,375		70,087
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	30,783		23,778		77,969		55,948
Natural Gas Distribution External Customers [Member]
Segment Reporting Information [Line Items]
Utility	138,149		105,130		862,073		794,311
Natural Gas Distribution Intercompany [Member]
Segment Reporting Information [Line Items]
Utility	0		0		0		8,047
Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	15		37		46		136
Investment Income, Interest	1	[1]	7	[1]	9	[1]	11	[1]
Interest expense, net of capitalized interest	193		425		792		917
Income tax provision (benefit)	1,949		(13,316)		8,632		25,506
Net Financial Earnings (Loss)	213		3,336		19,381		29,347
Energy Services External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	498,834		364,776		1,449,252		1,193,912
Energy Services Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility	1,579		24		55,010		13,254
Clean Energy Ventures [Member]
Segment Reporting Information [Line Items]
Nonutility	328		0		328		0
Depreciation and amortization	115		0		143		0
Interest expense, net of capitalized interest	14		0		21		0
Income tax provision (benefit)	(898)		0		(7,608)		0
Net Financial Earnings (Loss)	259		0		5,484		0
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	7,040		0		16,977		0
Midstream Assets [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	1		1		4		4
Investment Income, Interest	225	[1]	227	[1]	677	[1]	658	[1]
Interest expense, net of capitalized interest	803		380		2,428		2,037
Income tax provision (benefit)	1,281		1,173		3,951		3,073
Equity in earnings of affiliates	3,891		2,538		11,871		10,261
Net Financial Earnings (Loss)	1,847		1,828		5,705		5,218
Payments to Acquire Equity Method Investments	0		0		0		4,300
Retail and Other [Member]
Segment Reporting Information [Line Items]
Nonutility	10,951		10,058		26,903		19,803
Depreciation and amortization	191		159		602		475
Investment Income, Interest	1	[1]	(4)	[1]	2	[1]	3	[1]
Interest expense, net of capitalized interest	104		294		390		447
Income tax provision (benefit)	605		269		(439)		(1,751)
Net Financial Earnings (Loss)	1,401		314		913		(1,641)
Segment Reporting Information, Expenditures for Additions to Long-Lived Assets	1,012		367		2,975		460
Business Intersegment, Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility	(1,672)		(94)		(55,258)		(21,541)
Investment Income, Interest	(220)	[1]	(216)	[1]	(658)	[1]	(642)	[1]
Income tax provision (benefit)	(23)		(762)		(36)		(88)
Equity in earnings of affiliates	$ (934)		$ (557)		$ (2,387)		$ (2,376)

[1] Included in other income in the Unaudited Condensed Consolidated Statement of Operations.