CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Operating revenues	$ 701,549	$ 662,733	$ 3,507,243	$ 3,687,715
Purchased gas cost	(2,593)	44,550	960,571	1,449,010
Operation and maintenance expense	211,309	195,049	577,553	574,781
Depreciation and amortization expense	166,827	150,726	496,522	445,063
Taxes, other than income	105,739	103,155	302,235	305,784
Operating income	220,267	169,253	1,170,362	913,077
Other non-operating income	19,898	16,170	54,471	54,767
Interest charges	41,160	31,334	148,477	105,464
Income before income taxes	199,005	154,089	1,076,356	862,380
Income tax expense	33,441	16,282	167,477	95,042
Net income	$ 165,564	$ 137,807	$ 908,879	$ 767,338
Basic net income per share (USD per share)	$ 1.08	$ 0.94	$ 6.00	$ 5.33
Diluted net income per share (USD per share)	1.08	0.94	6.00	5.33
Cash dividends per share (USD per share)	$ 0.805	$ 0.740	$ 2.415	$ 2.220
Basic weighted average shares outstanding (in shares)	153,309	146,051	151,459	143,938
Diluted weighted average shares outstanding (in shares)	153,396	146,067	151,497	143,998
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax	$ (4)	$ (121)	$ 242	$ 100
Cash flow hedges:
Amortization and unrealized gains (losses) on interest rate agreements, net of tax	14,436	43,527	(8,638)	35,191
Total other comprehensive income (loss)	14,432	43,406	(8,396)	35,291
Total comprehensive income	179,996	181,213	900,483	802,629
Distribution segment
Operating revenues	632,446	615,259	3,325,459	3,554,389
Pipeline and storage segment
Operating revenues	69,103	47,474	181,784	133,326
Operating Segments | Distribution segment
Operating revenues	633,211	616,067	3,327,730	3,556,703
Purchased gas cost	179,510	206,048	1,464,815	1,896,986
Operation and maintenance expense	153,140	138,351	435,711	426,173
Depreciation and amortization expense	122,912	107,809	363,981	319,783
Taxes, other than income	94,527	92,180	273,430	275,002
Operating income	83,122	71,679	789,793	638,759
Other non-operating income	11,452	6,695	26,650	20,934
Interest charges	22,550	16,146	93,915	60,405
Income before income taxes	72,024	62,228	722,528	599,288
Income tax expense	6,175	2,589	92,550	56,707
Net income	65,849	59,639	629,978	542,581
Operating Segments | Pipeline and storage segment
Operating revenues	250,680	208,225	685,336	579,278
Purchased gas cost	(19)	(194)	825	(431)
Operation and maintenance expense	58,427	56,953	142,596	149,329
Depreciation and amortization expense	43,915	42,917	132,541	125,280
Taxes, other than income	11,212	10,975	28,805	30,782
Operating income	137,145	97,574	380,569	274,318
Other non-operating income	8,446	9,475	27,821	33,833
Interest charges	18,610	15,188	54,562	45,059
Income before income taxes	126,981	91,861	353,828	263,092
Income tax expense	27,266	13,693	74,927	38,335
Net income	99,715	78,168	278,901	224,757
Intersegment eliminations
Operating revenues	(182,342)	(161,559)	(505,823)	(448,266)
Purchased gas cost	(182,084)	(161,304)	(505,069)	(447,545)
Operation and maintenance expense	(258)	(255)	(754)	(721)
Depreciation and amortization expense	0	0	0	0
Taxes, other than income	0	0	0	0
Operating income	0	0	0	0
Other non-operating income	0	0	0	0
Interest charges	0	0	0	0
Income before income taxes	0	0	0	0
Income tax expense	0	0	0	0
Net income	0	0	0	0
Intersegment eliminations | Distribution segment
Operating revenues	(765)	(808)	(2,271)	(2,314)
Intersegment eliminations | Pipeline and storage segment
Operating revenues	$ (181,577)	$ (160,751)	$ (503,552)	$ (445,952)