Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net (loss) income	$ 154,464	$ 120,087
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	62,926	53,002
Deferred income tax (benefit) expense	(6,024)	56,285
Provision for uncollectible accounts	16,462	8,184
Regulatory impact from tax reform	24,098	0
Other, net	(1,635)	4,358
Net change in:
Accounts receivable and accrued utility revenues	(70,726)	(31,471)
Inventories	18,646	5,211
Deferred fuel and power costs, net of changes in unsettled derivatives	39,657	(12,571)
Accounts payable	3,655	2,775
Other current assets	(2,650)	9,014
Other current liabilities	16,725	21,727
Net cash provided by operating activities	255,598	236,601
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(217,901)	(201,916)
Net costs of property, plant and equipment disposals	(5,682)	(7,734)
Decrease (increase) in restricted cash	2,241	(1,941)
Net cash used by investing activities	(221,342)	(211,591)
CASH FLOWS FROM FINANCING ACTIVITIES
Payments of dividends	(45,000)	(40,000)
Issuances of long-term debt, net of issuance costs	124,404	99,499
Repayments of long-term debt	(44,182)	(20,000)
Decrease in short-term borrowings	(51,500)	(62,500)
Net cash used by financing activities	(16,278)	(23,001)
Cash and cash equivalents increase	17,978	2,009
CASH AND CASH EQUIVALENTS
End of period	23,181	4,828
Beginning of period	5,203	2,819
Increase	$ 17,978	$ 2,009