Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 116,041	$ 97,373	$ 121,055
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	72,332	67,303	63,590
Deferred income taxes, net	78,568	76,938	29,356
Pension contributions, net of pension cost	4,017	1,580	(1,415)
Settlement of interest rate protection agreements	0	(35,975)	0
Provision for uncollectible accounts	8,030	7,760	13,498
Other, net	9,664	(10,112)	3,228
Net change in:
Accounts receivable and accrued utility revenues	(25,253)	1,120	7,297
Inventories	(10,969)	9,376	43,503
Deferred fuel costs, net of changes in unsettled derivatives	(15,385)	(22,740)	51,778
Accounts payable	2,107	(3,053)	(7,649)
Other current assets	(2,108)	(70)	(9,723)
Other current liabilities	6,550	15,870	(7,808)
Net cash provided by operating activities	243,594	205,370	306,710
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(305,311)	(250,584)	(203,192)
Net costs of property, plant and equipment disposals	(12,735)	(7,940)	(10,443)
(Increase) decrease in restricted cash	(2,463)	6,019	(3,010)
Net cash used by investing activities	(320,509)	(252,505)	(216,645)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	(57,700)	(47,000)	(65,600)
Increase (decrease) in short-term borrowings	57,500	40,800	(14,600)
Issuances of long-term debt, net of issuance costs	99,499	298,379	0
Repayments of long-term debt	(20,000)	(247,000)	(20,000)
Excess tax benefits from equity-based payment arrangements	0	1,676	833
Net cash provided (used) by financing activities	79,299	46,855	(99,367)
Cash and cash equivalents increase (decrease)	2,384	(280)	(9,302)
CASH AND CASH EQUIVALENTS:
End of year	5,203	2,819	3,099
Beginning of year	2,819	3,099	12,401
Increase (decrease)	2,384	(280)	(9,302)
Cash paid (received) for:
Interest	29,449	36,155	38,405
Income taxes	$ 2,080	$ (19,758)	$ 54,427