Summary of Significant Accounting Policies Revenue Recognition and Remaining performance obligation (Details) - USD ($) $ in Millions		Sep. 30, 2021	Dec. 31, 2020
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Billed Contracts Receivable		$ 5.8	$ 4.4
Rail Products Group [Member] | Rail Products [Domain]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 1,228.4
Revenue, remaining performance obligation expected to be delivered in current year		31.80%
Rail Products Group [Member] | Rail Products [Domain] | External Customers
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 980.9
Rail Products Group [Member] | Rail Products [Domain] | Leasing
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		247.5
Rail Products Group [Member] | Sustainable Railcar Conversions
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	[1]	$ 98.3
Revenue, remaining performance obligation expected to be delivered in current year		25.80%
Rail Products Group [Member] | Maintenance services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 3.1
Revenue, remaining performance obligation expected to be delivered in current year		100.00%
Railcar Leasing and Management Services Group [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount		$ 81.2
Revenue, remaining performance obligation expected to be delivered in current year		8.10%

[1] During 2021, the Rail Products Group introduced a sustainable railcar conversion program whereby certain tank cars and freight cars are converted or upgraded to better meet the changing market demands.