Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 148,921	$ 116,041	$ 97,373
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	84,644	72,332	67,303
Deferred income taxes, net	61,934	78,568	76,938
Pension contributions, net of pension cost	(3,408)	4,017	1,580
Settlement of interest rate protection agreements	0	0	(35,975)
Provision for uncollectible accounts	17,970	8,030	7,760
Regulatory liability resulting from tax reform	24,430	0	0
Other, net	(3,778)	9,664	(10,112)
Net change in:
Accounts receivable and accrued utility revenues	(35,903)	(25,253)	1,120
Inventories	896	(10,969)	9,376
Deferred fuel and power costs, net of changes in unsettled derivatives	31,077	(15,385)	(22,740)
Accounts payable	3,987	2,107	(3,053)
Prepaid income taxes	(46,146)	(5,755)	8,070
Other current assets	5,402	3,647	(8,140)
Other current liabilities	(1,409)	6,550	15,870
Net cash provided by operating activities	288,617	243,594	205,370
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(323,538)	(305,311)	(250,584)
Net costs of property, plant and equipment disposals	(10,061)	(12,735)	(7,940)
Decrease (increase) in restricted cash	1,856	(2,463)	6,019
Net cash used by investing activities	(331,743)	(320,509)	(252,505)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	(50,000)	(57,700)	(47,000)
Increase in short-term borrowings	19,500	57,500	40,800
Issuances of long-term debt, net of issuance costs	124,404	99,499	298,379
Repayments of long-term debt	(45,667)	(20,000)	(247,000)
Excess tax benefits from equity-based payment arrangements	0	0	1,676
Net cash provided by financing activities	48,237	79,299	46,855
Cash and cash equivalents increase (decrease)	5,111	2,384	(280)
CASH AND CASH EQUIVALENTS:
End of year	10,314	5,203	2,819
Beginning of year	5,203	2,819
Increase (decrease)	5,111	2,384	(280)
Cash paid (received) for:
Interest	42,343	29,449	36,155
Income taxes	$ 24,306	$ 2,080	$ (19,758)