Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 100,444	$ 88,999
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	41,316	39,424
Deferred income taxes, net	23,369	21,269
Provision for uncollectible accounts	8,297	5,592
Other, net	4,647	(12,809)
Net change in:
Accounts receivable and accrued utility revenues	(34,052)	(5,354)
Inventories	13,336	65,850
Deferred fuel and power costs	20,549	8,133
Accounts payable	(4,183)	(23,032)
Other current assets	19,675	7,059
Other current liabilities	(4,753)	7,467
Net cash provided by operating activities	188,645	202,598
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(94,480)	(79,698)
Net costs of property, plant and equipment disposals	(2,604)	(2,400)
(Increase) decrease in restricted cash	(2,636)	2,704
Net cash used by investing activities	(99,720)	(79,394)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	0	(54,809)
Decrease in bank loans	(9,200)	0
Other	1,043	307
Net cash used by financing activities	(8,157)	(54,502)
Cash and cash equivalents increase	80,768	68,702
CASH AND CASH EQUIVALENTS:
End of period	82,027	75,969
Beginning of period	1,259	7,267
Increase	$ 80,768	$ 68,702