CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash Flows From Operating Activities
Net income	$ 244,671	$ 235,279
Depreciation and amortization:
Charged to depreciation and amortization	143,211	135,615
Charged to other accounts	645	566
Other
Deferred income taxes	132,456	131,292
Other	10,355	10,332
Net Assets Liabilities From Risk Management Activities	9,528	(29,091)
Net change in operating assets and liabilities	(85,090)	56,855
Net cash provided by operating activities	455,776	540,848
Cash Flows From Investing Activities
Capital expenditures	(538,233)	(441,644)
Other, net	1,888	(1,346)
Net cash used in investing activities	(536,345)	(442,990)
Cash Flows From Financing Activities
Net increase in short-term debt	169,002	21,839
Net proceeds from issuance of long-term debt	0	493,538
Settlement of interest rate agreements	0	13,364
Repayments of long-term debt	0	(500,000)
Cash dividends paid	(86,809)	(78,074)
Repurchase of equity awards	0	(7,985)
Issuance of common stock	17,641	12,727
Net cash provided by (used in) financing activities	99,834	(44,591)
Net increase in cash and cash equivalents	19,265	53,267
Cash and cash equivalents at beginning of period	28,653	42,258
Cash and cash equivalents at end of period	$ 47,918	$ 95,525