Summary of Significant Accounting Policies - Summary of Non-Utility Property (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 1,136.6	$ 1,052.1
Accumulated depreciation	(129.4)	(96.8)
Property, plant and equipment, net	1,007.2	955.3
Storage [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	453.8	382.0
Pipeline [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	498.3	492.4
All Other Property [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment	$ 184.5	$ 177.7