Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 99,248	$ 125,735
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	50,281	46,982
Deferred income tax expense (benefit)	66,136	(10,417)
Provision for uncollectible accounts	6,716	10,997
Settlement of interest rate protection agreements	(35,975)	0
Other, net	954	526
Net change in:
Accounts receivable and accrued utility revenues	(9,864)	(27,817)
Inventories	24,707	61,843
Deferred fuel and power costs, net of changes in unsettled derivatives	(11,587)	59,397
Accounts payable	(6,062)	(14,884)
Other current assets	(7,833)	631
Other current liabilities	17,763	47,939
Net cash provided by operating activities	194,484	300,932
CASH FLOWS FROM INVESTING ACTIVITIES
Expenditures for property, plant and equipment	(163,967)	(141,884)
Net costs of property, plant and equipment disposals	(7,664)	(6,358)
Decrease (increase) in restricted cash	6,390	(91)
Net cash used by investing activities	(165,241)	(148,333)
CASH FLOWS FROM FINANCING ACTIVITIES
Payment of dividends	(37,000)	(45,600)
Issuances of long-term debt	99,415	0
Repayments of long-term debt	(72,000)	(20,000)
Increase (decrease) in short-term borrowings	58,300	(83,600)
Other	1,392	722
Net cash provided (used) by financing activities	50,107	(148,478)
Cash and cash equivalents increase	79,350	4,121
CASH AND CASH EQUIVALENTS
End of period	82,449	16,522
Beginning of period	$ 3,099	$ 12,401