Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 86,645	$ 118,428
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	33,731	31,069
Deferred income tax expense (benefit)	48,905	(13,888)
Provision for uncollectible accounts	5,572	8,979
Other, net	2,138	2,521
Net change in:
Accounts receivable and accrued utility revenues	(66,130)	(154,515)
Inventories	35,031	75,686
Deferred fuel and power costs, net of changes in unsettled derivatives	(7,789)	55,760
Accounts payable	(3,882)	8,013
Other current assets	(2,529)	(921)
Other current liabilities	20,691	66,025
Net cash provided by operating activities	152,383	197,157
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(116,778)	(102,020)
Net costs of property, plant and equipment disposals	(5,101)	(3,694)
Decrease (increase) in restricted cash	2,693	(1,986)
Net cash used by investing activities	(119,186)	(107,700)
CASH FLOWS FROM FINANCING ACTIVITIES
Payment of dividends	(22,000)	(30,600)
Repayments of long-term debt	(72,000)	0
Increase (decrease) in short-term borrowings	83,300	(55,800)
Other	810	582
Net cash used by financing activities	(9,890)	(85,818)
Cash and cash equivalents increase	23,307	3,639
CASH AND CASH EQUIVALENTS
End of period	26,406	16,040
Beginning of period	$ 3,099	$ 12,401