BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Segment Reporting Information [Line Items]
Utility	$ 208,727		$ 233,469
Nonutility	615,397		644,936
Total operating revenues	824,124		878,405
Depreciation and amortization	14,386		12,566
Interest income	90	[1]	296	[1]
Interest expense, net of capitalized interest	7,195		6,295
Income tax provision (benefit)	40,867		1,505
Equity in earnings of affiliates	2,795		2,142
Net financial earnings (loss)	55,109		39,860
Capital expenditures	92,104		60,523
Investments in equity investees	547		0
Canada
Segment Reporting Information [Line Items]
Percentage to total operating revenues	4.70%		3.80%
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Investments in equity investees	547		0
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues	818,650		873,351
Depreciation and amortization	14,160		12,359
Interest income	329	[1]	529	[1]
Interest expense, net of capitalized interest	7,189		6,184
Income tax provision (benefit)	41,814		1,862
Net financial earnings (loss)	55,750		40,061
Capital expenditures	92,093		60,318
Operating Segments [Member] | Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	10,545		9,835
Interest income	90	[1]	261	[1]
Interest expense, net of capitalized interest	4,609		3,984
Income tax provision (benefit)	14,166		14,183
Net financial earnings (loss)	28,186		27,639
Capital expenditures	36,748		35,401
Operating Segments [Member] | Natural Gas Distribution [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Utility	208,727		233,469
Operating Segments [Member] | Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	22		12
Interest expense, net of capitalized interest	513		616
Income tax provision (benefit)	45,877		(11,273)
Net financial earnings (loss)	16,436		7,374
Operating Segments [Member] | Energy Services [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	600,562	[2]	633,691	[2]
Operating Segments [Member] | Energy Services [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility	3,126		4,018
Operating Segments [Member] | Clean Energy Ventures [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	3,591		2,511
Interest expense, net of capitalized interest	1,817		1,186
Income tax provision (benefit)	(19,721)		(2,044)
Net financial earnings (loss)	9,008		3,614
Capital expenditures	55,345		24,917
Operating Segments [Member] | Clean Energy Ventures [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	6,235		2,173
Operating Segments [Member] | Midstream Investments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	2		1
Interest income	239	[1]	268	[1]
Interest expense, net of capitalized interest	250		398
Income tax provision (benefit)	1,492		996
Equity in earnings of affiliates	3,775		2,942
Net financial earnings (loss)	2,120		1,434
Home Services and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	238		207
Interest income	0	[1]	0	[1]
Interest expense, net of capitalized interest	6		111
Income tax provision (benefit)	(452)		(191)
Net financial earnings (loss)	(592)		(201)
Capital expenditures	11		205
Home Services and Other [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	8,600		9,072
Home Services and Other [Member] | Intercompany [Member]
Segment Reporting Information [Line Items]
Nonutility	411		202
Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility	(3,537)		(4,220)
Depreciation and amortization	(12)		0
Interest income	(239)	[1]	(233)	[1]
Income tax provision (benefit)	(495)		(166)
Equity in earnings of affiliates	(980)		(800)
Net financial earnings (loss)	$ (49)		$ 0

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

[2] Includes sales to Canada, which accounted for 4.7 percent and 3.8 percent of total operating revenues during the three months ended December 31, 2014 and 2013, respectively.