Segment Information - Balance Sheet Information by Segment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting Information [Line Items]
Property, plant and equipment, net	$ 11,787,669	$ 10,371,147
Total assets	13,367,619	11,874,437
Operating Segments | Distribution
Segment Reporting Information [Line Items]
Property, plant and equipment, net	8,737,590	7,644,693
Total assets	12,579,741	11,109,128
Operating Segments | Pipeline and Storage
Segment Reporting Information [Line Items]
Property, plant and equipment, net	3,050,079	2,726,454
Total assets	3,279,323	2,963,480
Eliminations | Eliminations
Segment Reporting Information [Line Items]
Property, plant and equipment, net	0	0
Total assets	$ (2,491,445)	$ (2,198,171)