Description of Business (Details) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2024 USD ($) Segment	Jun. 30, 2023 USD ($)
Schedule of Equity Method Investments [Line Items]
Number of business segments \| Segment			3
Net gain on asset dispositions	$ 25.6	$ 41.1	$ 61.8	$ 88.2
Asset Impairment Charges			0.0	1.2
Portfolio Investments and Capital Additions	442.0	486.6	820.6	873.6
Rail International
Schedule of Equity Method Investments [Line Items]
Net gain on asset dispositions	0.7	0.7	2.0	1.5
Asset Impairment Charges				0.0
Portfolio Investments and Capital Additions	$ 59.6	$ 77.3	$ 109.5	$ 158.4

Portfolio Investments and Capital Additions

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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Amount of gain (loss) from the difference between the sale price or salvage price and the book value of an asset that was sold or retired, and gain (loss) from the write down of assets from their carrying value to fair value.

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- Definition

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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