Condensed Consolidated Statements of Cash Flows (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 38,839us-gaap_NetIncomeLoss	$ 45,286us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash from operating activities:
Depreciation and amortization	15,425	14,450
Deferred income taxes, net	3,921us-gaap_DeferredIncomeTaxExpenseBenefit	5,157us-gaap_DeferredIncomeTaxExpenseBenefit
Provision for uncollectible accounts	2,490us-gaap_ProvisionForDoubtfulAccounts	2,249us-gaap_ProvisionForDoubtfulAccounts
Other, net	3,534us-gaap_OtherNoncashIncomeExpense	(124)us-gaap_OtherNoncashIncomeExpense
Net change in:
Accounts receivable and accrued utility revenues	(92,313)	(114,184)
Inventories	9,790us-gaap_IncreaseDecreaseInInventories	8,985us-gaap_IncreaseDecreaseInInventories
Deferred fuel and power costs, net of changes in unsettled derivatives	4,393	2,086
Accounts payable	6,075	13,198
Other current assets	(4,821)	802
Other current liabilities	25,356	24,405
Net cash provided by operating activities	12,689	2,310
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for property, plant and equipment	(55,029)	(34,254)
Net costs of property, plant and equipment disposals	(2,028)	(1,491)
(Increase) decrease in restricted cash	(5,371)	3,181
Net cash used by investing activities	(62,428)	(32,564)
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of dividends	(15,600)us-gaap_PaymentsOfDividendsCommonStock	(17,536)us-gaap_PaymentsOfDividendsCommonStock
Increase in short-term borrowings	67,200	56,000
Other	5	91
Net cash provided by financing activities	51,605	38,555
Cash and cash equivalents increase	1,866	8,301
CASH AND CASH EQUIVALENTS:
End of period	14,267	13,008
Beginning of period	12,401	4,707
Increase	$ 1,866	$ 8,301

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