BUSINESS SEGMENT AND OTHER OPERATIONS DATA - RECONCILIATION OF SEGMENT INCOME TO CONSOLIDATED (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Utility	$ 233,469		$ 218,849
Nonutility	644,936		517,170
Total operating revenues	878,405		736,019
Depreciation and amortization	12,566		11,303
Interest income	296	[1]	207	[1]
Interest expense, net of capitalized interest	6,295		5,825
Income tax provision (benefit)	1,505		23,980
Equity in earnings of affiliates	2,142		2,555
Net financial earnings (loss)	39,860		35,493
Capital expenditures	60,523		49,619
Intercompany/Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility	(4,220)		(369)
Depreciation and amortization	0		(9)
Interest income	(233)	[1]	(232)	[1]
Income tax provision (benefit)	(166)		(42)
Equity in earnings of affiliates	(800)		(936)
Net financial earnings (loss)	0		(9)
Natural Gas Distribution [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	9,835		9,277
Interest income	261	[1]	167	[1]
Interest expense, net of capitalized interest	3,984		3,584
Income tax provision (benefit)	14,183		14,507
Net financial earnings (loss)	27,639		25,492
Capital expenditures	35,401		34,145
Natural Gas Distribution [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Utility	233,469		218,849
Energy Services [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	12		11
Interest income	0	[1]	0	[1]
Interest expense, net of capitalized interest	616		568
Income tax provision (benefit)	(11,273)		16,164
Net financial earnings (loss)	7,374		3,014
Energy Services [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	633,691	[2]	503,635	[2]
Energy Services [Member] | Intercompany/Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility	4,018		107
Clean Energy Ventures [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	2,511		1,831
Interest expense, net of capitalized interest	1,186		783
Income tax provision (benefit)	(2,044)		(7,769)
Net financial earnings (loss)	3,614		5,305
Capital expenditures	24,917		15,320
Clean Energy Ventures [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	2,173		3,179
Midstream Investments [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	1		2
Interest income	268	[1]	271	[1]
Interest expense, net of capitalized interest	398		591
Income tax provision (benefit)	996		1,243
Equity in earnings of affiliates	2,942		3,491
Net financial earnings (loss)	1,434		1,785
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total operating revenues	873,351		725,770
Depreciation and amortization	12,359		11,121
Interest income	529	[1]	438	[1]
Interest expense, net of capitalized interest	6,184		5,526
Income tax provision (benefit)	1,862		24,145
Net financial earnings (loss)	40,061		35,596
Capital expenditures	60,318		49,465
Retail and Other [Member]
Segment Reporting Information [Line Items]
Depreciation and amortization	207		191
Interest income	0	[1]	1	[1]
Interest expense, net of capitalized interest	111		299
Income tax provision (benefit)	(191)		(123)
Net financial earnings (loss)	(201)		(94)
Capital expenditures	205		154
Retail and Other [Member] | External Customers [Member]
Segment Reporting Information [Line Items]
Nonutility	9,072		10,355
Retail and Other [Member] | Intercompany/Eliminations [Member]
Segment Reporting Information [Line Items]
Nonutility	$ 202		$ 263
Canada
Segment Reporting Information [Line Items]
Percentage to total operating revenues	3.80%		7.60%

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

[2] Includes sales to Canada, which accounted for 3.8 percent and 7.6 percent of total operating revenues during the three months ended December 31, 2013 and 2012, respectively.