Summary of Significant Accounting Policies Revenue Recognition and Remaining performance obligation (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Rail Products Group [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Billed Contracts Receivable	$ 6.2	$ 12.6
Rail Products Group [Member] | Rail Products [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,938.9
Revenue, remaining performance obligation expected to be delivered in current year	49.10%
Rail Products Group [Member] | Rail Products [Domain] | External Customers
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,626.3
Rail Products Group [Member] | Rail Products [Domain] | Leasing & Services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	312.6
Rail Products Group [Member] | Sustainable Railcar Conversions
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 35.8
Revenue, remaining performance obligation expected to be delivered in current year	91.50%
Leasing & Services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Billed Contracts Receivable	$ 17.4	$ 8.8
Leasing & Services | Leasing and Management [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 62.7
Revenue, remaining performance obligation expected to be delivered in current year	21.40%
Leasing & Services | Maintenance services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 7.9
Revenue, remaining performance obligation expected to be delivered in current year	100.00%