Condensed Consolidated Statements of Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011
Revenues	$ 345,802	$ 484,465	$ 626,443	$ 834,981
Costs and expenses:
Cost of sales — gas, fuel and purchased power (excluding depreciation shown below)	192,770	308,778	349,676	522,262
Operating and administrative expenses	45,749	51,299	86,691	91,193
Operating and administrative expenses - related parties	2,781	5,923	4,906	8,848
Taxes other than income taxes	4,857	5,469	8,984	9,827
Depreciation	12,328	12,683	24,707	25,289
Amortization	782	633	1,466	1,265
Other income, net	(1,912)	(4,429)	(3,039)	(6,692)
Total costs and expenses	257,355	380,356	473,391	651,992
Operating income	88,447	104,109	153,052	182,989
Interest expense	10,677	10,809	21,284	21,442
Income before income taxes	77,770	93,300	131,768	161,547
Income taxes	29,899	33,137	51,229	60,310
Net income	$ 47,871	$ 60,163	$ 80,539	$ 101,237