CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Operating revenues	$ 1,342,585	$ 1,175,999
Purchased gas cost	295,999	234,048
Operation and maintenance expense	229,810	207,044
Depreciation and amortization expense	194,645	180,533
Taxes, other than income	107,367	94,894
Operating income	514,764	459,480
Other non-operating income	22,231	24,634
Interest charges	33,413	52,925
Income before income taxes	503,582	431,189
Income tax expense	100,618	79,331
Net income	$ 402,964	$ 351,858
Basic net income per share (USD per share)	$ 2.48	$ 2.25
Diluted net income per share (USD per share)	2.44	2.23
Cash dividends per share (USD per share)	$ 1.00	$ 0.87
Basic weighted average shares outstanding (in shares)	162,727	156,301
Diluted weighted average shares outstanding (in shares)	164,871	157,824
Other comprehensive income (loss), net of tax
Net unrealized holding gains (losses) on available-for-sale securities, net of tax	$ 1	$ (138)
Cash flow hedges:
Amortization and unrealized gains (losses) on interest rate agreements, net of tax	(4,806)	16,561
Total other comprehensive income (loss)	(4,805)	16,423
Total comprehensive income	398,159	368,281
Distribution segment
Operating revenues	1,258,049	1,108,569
Depreciation and amortization expense	145,988	133,627
Interest charges	24,445	34,249
Income tax expense	61,142	51,670
Net income	269,235	240,213
Pipeline and storage segment
Operating revenues	84,536	67,430
Depreciation and amortization expense	48,657	46,906
Interest charges	8,968	18,676
Income tax expense	39,476	27,661
Net income	133,729	111,645
Operating Segments
Operating revenues	1,545,459	1,364,725
Operating Segments | Distribution segment
Operating revenues	1,258,826	1,109,335
Purchased gas cost	497,036	422,570
Operating Segments | Pipeline and storage segment
Operating revenues	286,633	255,390
Purchased gas cost	1,567	(58)
Intersegment Eliminations
Operating revenues	(202,874)	(188,726)
Purchased gas cost	(202,604)	(188,464)
Intersegment Eliminations | Distribution segment
Operating revenues	(777)	(766)
Intersegment Eliminations | Pipeline and storage segment
Operating revenues	$ (202,097)	$ (187,960)