Segment Information - Schedule of Income Statements and Capital Expenditures By Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Operating revenues	$ 1,342,585	$ 1,175,999
Operation and maintenance expense	223,960	198,630
Depreciation and amortization expense	194,645	180,533
Interest charges	33,413	52,925
Income tax expense	100,618	79,331
Other segment items	589,859	501,448
Net income	402,964	351,858
Capital expenditures	1,033,347	891,191
Distribution
Segment Reporting Information [Line Items]
Operating revenues	1,258,049	1,108,569
Operation and maintenance expense	165,368	145,896
Depreciation and amortization expense	145,988	133,627
Interest charges	24,445	34,249
Income tax expense	61,142	51,670
Other segment items	592,648	503,680
Net income	269,235	240,213
Capital expenditures	804,575	625,649
Pipeline and Storage
Segment Reporting Information [Line Items]
Operating revenues	84,536	67,430
Operation and maintenance expense	58,592	52,734
Depreciation and amortization expense	48,657	46,906
Interest charges	8,968	18,676
Income tax expense	39,476	27,661
Other segment items	(2,789)	(2,232)
Net income	133,729	111,645
Capital expenditures	228,772	265,542
Operating Segments
Segment Reporting Information [Line Items]
Operating revenues	1,545,459	1,364,725
Operating Segments | Distribution
Segment Reporting Information [Line Items]
Operating revenues	1,258,826	1,109,335
Operating Segments | Pipeline and Storage
Segment Reporting Information [Line Items]
Operating revenues	286,633	255,390
Intersegment Eliminations
Segment Reporting Information [Line Items]
Operating revenues	(202,874)	(188,726)
Intersegment Eliminations | Distribution
Segment Reporting Information [Line Items]
Operating revenues	(777)	(766)
Intersegment Eliminations | Pipeline and Storage
Segment Reporting Information [Line Items]
Operating revenues	$ (202,097)	$ (187,960)