Other Matters - Sale of Certain Railcars (Details) $ in Millions				6 Months Ended
	May 16, 2025 USD ($)	Apr. 30, 2025 USD ($)	Apr. 14, 2025 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2025
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Total number of railcars to be sold					135
Number of railcars sold	68
Total consideration	$ 2.1	$ 156.3	$ 40.3	$ 6.7
Gain on disposal or impairment of assets, net		$ 55.7	$ 1.0
Certain Railcars
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations
Gain on disposal or impairment of assets, net	$ 0.1			$ 2.1