Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 132,748	$ 157,487
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	44,815	41,512
Deferred income tax expense (benefit), net	6,966	(1,619)
Provision for uncollectible accounts	11,078	13,142
Other, net	3,881	(345)
Net change in:
Accounts receivable and accrued utility revenues	(134,022)	(176,795)
Inventories	32,471	33,592
Deferred fuel and power costs, net of changes in unsettled derivatives	(16,951)	31,481
Accounts payable	16,252	17,302
Other current assets	59,962	(3,791)
Other current liabilities	3,764	23,090
Net cash provided by operating activities	160,964	135,056
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(177,338)	(151,468)
Net costs of property, plant and equipment disposals	(2,769)	(3,397)
Net cash used by investing activities	(180,107)	(154,865)
CASH FLOWS FROM FINANCING ACTIVITIES
Payment of dividends	(10,000)	(30,000)
Issuances of long-term debt, net of issuance costs	149,211	124,404
Repayments of long-term debt	(4,814)	(41,562)
Decrease in short-term borrowings	(84,500)	(35,000)
Net cash provided by financing activities	49,897	17,842
CASH AND CASH EQUIVALENTS
Cash, cash equivalents, and restricted cash, period end	42,258	6,282
Cash, cash equivalents, and restricted cash, period beginning	11,504	8,249
Cash, cash equivalents and restricted cash increase (decrease)	$ 30,754	$ (1,967)