Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 88,999	$ 106,715
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	39,424	39,243
Deferred income taxes, net	21,269	18,700
Provision for uncollectible accounts	5,592	9,495
Other, net	(12,809)	8,712
Net change in:
Accounts receivable and accrued utility revenues	(5,354)	(23,902)
Inventories	65,850	60,107
Deferred fuel and power costs	8,133	32,951
Accounts payable	(23,032)	(3,688)
Other current assets	7,059	5,340
Other current liabilities	7,467	(17,988)
Net cash provided by operating activities	202,598	235,685
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(79,698)	(59,590)
Net costs of property, plant and equipment disposals	(2,400)	(1,414)
Decrease in restricted cash	2,704	643
Net cash used by investing activities	(79,394)	(60,361)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	(54,809)	(54,419)
Decrease in bank loans	0	(17,000)
Other	307	691
Net cash used by financing activities	(54,502)	(70,728)
Cash and cash equivalents increase	68,702	104,596
CASH AND CASH EQUIVALENTS:
End of period	75,969	108,914
Beginning of period	7,267	4,318
Increase	$ 68,702	$ 104,596