Summary of Significant Accounting Policies Revenue Recognition and Remaining performance obligation (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Contract Receivable	$ 10.8	$ 10.2
Rail Group | Railcars
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 3,252.7
Revenue, remaining performance obligation expected to be delivered in current year	59.00%
Rail Group | Railcars | External Customers
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 2,038.9
Rail Group | Railcars | Leasing
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	1,213.8
Revenue, Remaining Performance Obligation, Amount	240.0
Rail Group | Maintenance services
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 77.6
Revenue, remaining performance obligation expected to be delivered in current year	100.00%
Railcar Leasing and Management Services Group
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 107.4
Revenue, remaining performance obligation expected to be delivered in current year	17.00%