CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES
Net Income	$ 665,563	$ 601,443	$ 511,406
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	477,977	429,828	391,456
Deferred income taxes	155,355	155,322	132,004
One-time income tax benefit	0	(20,962)	0
Stock-based compensation	11,255	9,583	11,121
Amortization of debt issuance costs	14,030	11,543	9,464
Equity component of AFUDC	(32,749)	(23,493)	(11,165)
Other	3,731	8,411	1,169
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	(113,665)	7,167	18,724
(Increase) decrease in gas stored underground	(66,166)	18,188	35,594
Increase in Winter Storm Uri current regulatory asset (see Note 9)	(2,003,659)	0	0
Increase in other current assets	(84,705)	(35,878)	(26,590)
Increase in Winter Storm Uri long-term regulatory asset (see Note 9)	(76,652)	0	0
(Increase) decrease in deferred charges and other assets	136,809	(31,935)	(58,403)
Increase in accounts payable and accrued liabilities	104,242	7,359	9,908
Decrease in other current liabilities	(166,268)	(129,543)	(103,895)
Increase (decrease) in deferred credits and other liabilities	(109,349)	30,966	47,976
Net cash provided by (used in) operating activities	(1,084,251)	1,037,999	968,769
CASH FLOWS USED IN INVESTING ACTIVITIES
Capital expenditures	(1,969,540)	(1,935,676)	(1,693,477)
Proceeds from the sale of discontinued operations	0	0	4,000
Purchases of debt and equity securities	(49,879)	(50,517)	(29,153)
Proceeds from sale of debt and equity securities	14,957	32,339	6,070
Maturities of debt securities	28,850	18,669	20,299
Other, net	11,957	9,667	8,601
Net cash used in investing activities	(1,963,655)	(1,925,518)	(1,683,660)
CASH FLOWS FROM FINANCING ACTIVITIES
Net decrease in short-term debt	0	(464,915)	(110,865)
Proceeds from issuance of long-term debt, net of premium/discount	2,797,346	999,450	1,045,221
Net proceeds from equity offering	606,667	624,302	694,103
Issuance of common stock through stock purchase and employee retirement plans	15,841	19,548	19,323
Settlement of interest rate swaps	62,159	(4,426)	(90,141)
Repayment of long-term debt	0	0	(575,000)
Cash dividends paid	(323,904)	(282,444)	(245,717)
Debt issuance costs	(14,288)	(7,738)	(11,254)
Net cash provided by financing activities	3,143,821	883,777	725,670
Net increase (decrease) in cash and cash equivalents	95,915	(3,742)	10,779
Cash and cash equivalents at beginning of year	20,808	24,550	13,771
Cash and cash equivalents at end of year	$ 116,723	$ 20,808	$ 24,550