Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 120,087	$ 99,248
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	53,002	50,281
Deferred income tax expense	56,285	66,136
Provision for uncollectible accounts	8,184	6,716
Settlement of interest rate protection agreements	0	(35,975)
Other, net	4,358	954
Net change in:
Accounts receivable and accrued utility revenues	(31,471)	(9,864)
Inventories	5,211	24,707
Deferred fuel and power costs, net of changes in unsettled derivatives	(12,571)	(11,587)
Accounts payable	2,775	(6,062)
Other current assets	9,014	(7,833)
Other current liabilities	21,727	17,763
Net cash provided by operating activities	236,601	194,484
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(201,916)	(163,967)
Net costs of property, plant and equipment disposals	(7,734)	(7,664)
(Increase) decrease in restricted cash	(1,941)	6,390
Net cash used by investing activities	(211,591)	(165,241)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments of dividends	(40,000)	(37,000)
Issuances of long-term debt, net of issuance costs	99,499	99,415
Repayments of long-term debt	(20,000)	(72,000)
(Decrease) increase in short-term borrowings	(62,500)	58,300
Other	0	1,392
Net cash (used) provided by financing activities	(23,001)	50,107
Cash and cash equivalents increase	2,009	79,350
CASH AND CASH EQUIVALENTS
End of period	4,828	82,449
Beginning of period	2,819	3,099
Increase	$ 2,009	$ 79,350