CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) (USD $)	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Cash Flows From Operating Activities
Net income (loss)	$ 97,595,000	$ 87,016,000
Depreciation and amortization:
Charged to depreciation and amortization	67,593,000	60,469,000
Charged to other accounts	275,000	221,000
Other
Deferred income taxes	55,418,000	47,127,000
Other	4,889,000	5,228,000
Net Assets Liabilities From Risk Management Activities	(20,828,000)	(5,477,000)
Net change in operating assets and liabilities	(177,527,000)	(160,284,000)
Net cash provided by operating activities	27,415,000	34,300,000
Cash Flows From Investing Activities
Capital expenditures	(261,313,000)	(180,567,000)
Other, net	(739,000)	(5,867,000)
Net cash used in investing activities	(262,052,000)	(186,434,000)
Cash Flows From Financing Activities
Net decrease in short-term debt	350,574,000	320,783,000
Net proceeds from issuance of long-term debt	493,538,000	0
Settlement of interest rate agreements	13,364,000	0
Repayments of long-term debt	(500,000,000)	0
Cash dividends paid	(39,592,000)	(33,984,000)
Repurchase of equity awards	(7,985,000)	(6,289,000)
Issuance of common stock	6,312,000	(12,000)
Net cash provided by (used in) financing activities	316,211,000	280,498,000
Net increase (decrease) in cash and cash equivalents	81,574,000	128,364,000
Cash and cash equivalents at beginning of period	42,258,000	66,199,000
Cash and cash equivalents at end of period	$ 123,832,000	$ 194,563,000