Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 109,390	$ 86,645
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	35,090	33,731
Deferred income tax expense	35,992	48,905
Provision for uncollectible accounts	6,265	5,572
Other, net	6,292	2,138
Net change in:
Accounts receivable and accrued utility revenues	(110,111)	(66,130)
Inventories	25,166	35,031
Deferred fuel and power costs, net of changes in unsettled derivatives	(7,601)	(7,789)
Accounts payable	14,722	(3,882)
Other current assets	(948)	(2,529)
Other current liabilities	17,591	20,691
Net cash provided by operating activities	131,848	152,383
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(135,075)	(116,778)
Net costs of property, plant and equipment disposals	(5,753)	(5,101)
Decrease in restricted cash	236	2,693
Net cash used by investing activities	(140,592)	(119,186)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments of dividends	(25,000)	(22,000)
Issuances of long-term debt, net of issuance costs	99,491	0
Repayments of long-term debt	0	(72,000)
(Decrease) increase in short-term borrowings	(64,000)	83,300
Other	0	810
Net cash provided (used) by financing activities	10,491	(9,890)
Cash and cash equivalents increase	1,747	23,307
CASH AND CASH EQUIVALENTS
End of period	4,566	26,406
Beginning of period	2,819	3,099
Increase	$ 1,747	$ 23,307