Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 95,071	$ 80,539
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	27,283	26,173
Deferred income taxes, net	4,241	12,229
Provision for uncollectible accounts	6,059	5,819
Other, net	7,537	(10,663)
Net change in:
Accounts receivable and accrued utility revenues	(136,644)	(62,385)
Inventories	51,119	80,623
Deferred fuel and power costs	33,311	14,039
Accounts payable	3,688	(28,996)
Other current assets	12,632	786
Other current liabilities	18,120	11,202
Net cash provided by operating activities	122,417	129,366
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(55,519)	(49,784)
Net costs of property, plant and equipment disposals	(1,437)	(1,541)
Decrease in restricted cash	0	48
Net cash used by investing activities	(56,956)	(51,277)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	0	(39,004)
Decrease in bank loans	(9,200)	0
Other	809	241
Net cash used by financing activities	(8,391)	(38,763)
Cash and cash equivalents increase	57,070	39,326
CASH AND CASH EQUIVALENTS:
End of period	58,329	46,593
Beginning of period	1,259	7,267
Increase	$ 57,070	$ 39,326