Segment Information - Balance Sheet Information by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 13,355,347	$ 11,787,669
Total assets	15,359,032	13,367,619
Operating Segments | Distribution
Segment Reporting Information [Line Items]
Property, plant and equipment, net	9,944,978	8,737,590
Total assets	14,578,176	12,579,741
Operating Segments | Pipeline and Storage
Segment Reporting Information [Line Items]
Property, plant and equipment, net	3,410,369	3,050,079
Total assets	3,647,907	3,279,323
Eliminations
Segment Reporting Information [Line Items]
Property, plant and equipment, net	0	0
Total assets	$ (2,867,051)	$ (2,491,445)