CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 511,406	$ 603,064	$ 396,421
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	391,456	361,083	319,633
Deferred income taxes	132,004	158,271	227,183
One-time income tax benefit	0	(158,782)	0
Gain on sale of discontinued operations	0	0	(12,931)
Discontinued cash flow hedging for commodity contracts	0	0	(10,579)
Stock-based compensation	11,121	12,863	14,064
Amortization of debt issuance costs	9,464	7,865	6,469
Equity Component of AFUDC	(11,165)	0	0
Other	1,169	5,437	97
Changes in assets and liabilities:
(Increase) decrease in accounts receivable	18,724	(29,208)	(58,696)
(Increase) decrease in gas stored underground	35,594	18,921	(35,126)
(Increase) decrease in other current assets	(26,590)	60,424	9,991
(Increase) decrease in deferred charges and other assets	(58,403)	(10,049)	102,254
Increase (decrease) in accounts payable and accrued liabilities	9,908	(11,857)	53,017
Increase (decrease) in other current liabilities	(103,895)	74,707	(78,651)
Increase (decrease) in deferred credits and other liabilities	47,976	31,923	(66,056)
Net cash provided by operating activities	968,769	1,124,662	867,090
CASH FLOWS USED IN INVESTING ACTIVITIES
Capital expenditures	(1,693,477)	(1,467,591)	(1,137,089)
Acquisition	0	0	(86,128)
Proceeds from the sale of discontinued operations	4,000	3,000	140,253
Purchases of debt and equity securities	(29,153)	(46,401)	(53,597)
Proceeds from sale of debt and equity securities	6,070	22,360	31,792
Maturities of debt securities	20,299	15,716	9,332
Use tax refund	0	790	29,790
Other, net	8,601	8,560	9,341
Net cash used in investing activities	(1,683,660)	(1,463,566)	(1,056,306)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term debt	(110,865)	128,035	(382,066)
Proceeds from issuance of long-term debt, net of premium/discount	1,045,221	0	884,911
Net proceeds from equity offering	694,103	395,092	98,755
Issuance of common stock through stock purchase and employee retirement plans	19,323	19,563	26,523
Settlement of interest rate swaps	(90,141)	0	(36,996)
Interest rate swaps cash collateral	0	0	25,670
Repayment of long-term debt	(575,000)	0	(250,000)
Cash dividends paid	(245,717)	(214,906)	(191,931)
Debt issuance costs	(11,254)	0	(6,775)
Other	0	(1,518)	0
Net cash provided by financing activities	725,670	326,266	168,091
Net increase (decrease) in cash and cash equivalents	10,779	(12,638)	(21,125)
Cash and cash equivalents at beginning of year	13,771	26,409	47,534
Cash and cash equivalents at end of year	$ 24,550	$ 13,771	$ 26,409