Segment Information - Balance Sheet Information by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 15,063,970	$ 13,355,347
Total assets	19,608,662	15,359,032
Operating Segments | Distribution
Segment Reporting Information [Line Items]
Property, plant and equipment, net	11,232,649	9,944,978
Total assets	18,847,266	14,578,176
Operating Segments | Pipeline and Storage
Segment Reporting Information [Line Items]
Property, plant and equipment, net	3,831,321	3,410,369
Total assets	4,076,844	3,647,907
Eliminations
Segment Reporting Information [Line Items]
Property, plant and equipment, net	0	0
Total assets	$ (3,315,448)	$ (2,867,051)