Income Taxes Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Income Tax Disclosure [Line Items]
Effective Income Tax Rate Reconciliation, Percent	15.80%	22.70%	18.40%	23.80%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%	21.00%
Deferred income taxes	$ 1,070.8		$ 1,070.8		$ 1,075.6
Inflation Reduction Act - Purchase of Federal Tax Credits	40.0		40.0
Inflation Reduction Act - Payment to Acquire Federal Tax Credits	38.4		38.4
Effective Income Tax Rate Reconciliation, Tax Credit, Amount	1.6		1.6
Railcars on Lease [Member]
Income Tax Disclosure [Line Items]
Deferred income taxes	$ 1,100.0		$ 1,100.0		$ 1,100.0

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Inflation Reduction Act - Payment to Acquire Federal Tax Credits

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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