Condensed Consolidated Statements of Income (Unaudited) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Condensed Consolidated Statements of Income [Abstract]
Revenues	$ 172,714	$ 175,021	$ 1,007,695	$ 1,014,497
Costs and expenses:
Cost of sales - gas, fuel and purchased power (excluding depreciation shown below)	93,383	98,864	615,645	642,252
Operating and administrative expenses	42,910	40,515	134,103	133,369
Operating and administrative expenses - related parties	1,747	2,792	10,595	10,549
Taxes other than income taxes	3,523	4,167	13,350	13,589
Depreciation	12,058	12,728	37,347	37,847
Amortization	631	709	1,896	2,087
Other income, net	(1,024)	(1,133)	(7,716)	(5,185)
Total costs and expenses	153,228	158,642	805,220	834,508
Operating income	19,486	16,379	202,475	179,989
Interest expense	10,518	10,481	31,960	31,842
Income before income taxes	8,968	5,898	170,515	148,147
Income taxes	3,490	2,294	63,800	58,768
Net income	$ 5,478	$ 3,604	$ 106,715	$ 89,379