CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash Flows From Operating Activities
Net income	$ 616,843	$ 536,110
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization expense	353,269	318,082
Deferred income taxes	144,195	137,996
One-time income tax benefit	0	(20,962)
Other	378	5,935
Net assets / liabilities from risk management activities	(99)	1,295
Net change in Winter Storm Uri regulatory asset (See Note 8)	(2,088,536)	0
Net change in other operating assets and liabilities	(184,517)	(82,970)
Net cash provided by (used in) operating activities	(1,158,467)	895,486
Cash Flows From Investing Activities
Capital expenditures	(1,357,960)	(1,405,673)
Debt and equity securities activities, net	(2,363)	(692)
Other, net	8,006	6,098
Net cash used in investing activities	(1,352,317)	(1,400,267)
Cash Flows From Financing Activities
Net decrease in short-term debt	0	(464,915)
Net proceeds from equity offering	460,678	358,047
Issuance of common stock through stock purchase and employee retirement plans	12,121	14,125
Proceeds from issuance of long-term debt	2,797,346	999,450
Cash dividends paid	(241,260)	(210,674)
Debt issuance costs	(14,288)	(7,738)
Net cash provided by financing activities	3,014,597	688,295
Net increase in cash and cash equivalents	503,813	183,514
Cash and cash equivalents at beginning of period	20,808	24,550
Cash and cash equivalents at end of period	$ 524,621	$ 208,064