CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows From Operating Activities
Net income	$ 418,319	$ 372,534
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	210,978	192,837
Deferred income taxes	110,664	96,885
Other	7,144	5,334
Net assets / liabilities from risk management activities	1,310	(333)
Net change in operating assets and liabilities	(114,640)	(106,428)
Net cash provided by operating activities	633,775	560,829
Cash Flows From Investing Activities
Capital expenditures	(994,737)	(777,586)
Proceeds from the sale of discontinued operations	0	4,000
Debt and equity securities activities, net	(1,131)	777
Other, net	4,631	4,388
Net cash used in investing activities	(991,237)	(768,421)
Cash Flows From Financing Activities
Net decrease in short-term debt	(264,992)	(575,780)
Net proceeds from equity offering	258,047	494,085
Issuance of common stock through stock purchase and employee retirement plans	8,321	10,344
Proceeds from issuance of long-term debt	799,450	1,045,221
Settlement of interest rate swaps	0	(90,141)
Repayment of long-term debt	0	(450,000)
Cash dividends paid	(140,077)	(120,328)
Debt issuance costs	(7,738)	(11,227)
Net cash provided by financing activities	653,011	302,174
Net increase in cash and cash equivalents	295,549	94,582
Cash and cash equivalents at beginning of period	24,550	13,771
Cash and cash equivalents at end of period	$ 320,099	$ 108,353