CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows From Operating Activities
Net income	$ 360,568	$ 315,864
Adjustments to reconcile net income to net cash provided by operating activities:
Charged to depreciation and amortization	234,833	216,670
Deferred income taxes	188,256	171,042
Gain on sale of discontinued operations	(12,931)	0
Discontinued cash flow hedging for natural gas marketing commodity contracts	(10,579)	0
Other	14,892	14,430
Net assets / liabilities from risk management activities	25,661	7,973
Net change in operating assets and liabilities	(55,139)	(96,033)
Net cash provided by operating activities	745,561	629,946
Cash Flows From Investing Activities
Capital expenditures	(812,148)	(789,688)
Acquisition	(86,128)	0
Proceeds from the sale of discontinued operations	140,253	0
Available-for-sale securities activities, net	(14,329)	558
Use tax refund	18,562	0
Other, net	6,435	5,731
Net cash used in investing activities	(747,355)	(783,399)
Cash Flows From Financing Activities
Net increase in short-term debt	(571,238)	212,539
Net proceeds from equity offering	98,755	98,660
Issuance of common stock through stock purchase and employee retirement plans	22,673	26,500
Proceeds from issuance of long-term debt, net of discount	884,911	0
Settlement of interest rate agreements	(36,996)	0
Repayments of long-term debt	(250,000)	0
Interest rate agreements cash collateral	25,670	(16,330)
Cash dividends paid	(143,075)	(130,363)
Other	(6,663)	0
Net cash provided by (used in) financing activities	24,037	191,006
Net increase (decrease) in cash and cash equivalents	22,243	37,553
Cash and cash equivalents at beginning of period	47,534	28,653
Cash and cash equivalents at end of period	$ 69,777	$ 66,206