Railcar Leasing and Management Services Group - Future operating lease obligations and future contractual minimum rental revenues (Details) - Railcar Leasing and Management Services Group $ in Millions	Mar. 31, 2018 USD ($)
Railroad transportation equipment leased from independent owner trusts
Future operating lease obligations
Remaining nine months of 2018	$ 21.9
2018	28.8
2019	26.1
2020	26.1
2021	24.9
Thereafter	93.0
Total	220.8
Future contractual minimum rental revenues
Remaining nine months of 2018	30.8
2018	28.8
2019	18.7
2020	13.1
2021	8.9
Thereafter	7.7
Total	108.0
Operating leases other than leases with the Trusts
Future operating lease obligations
Remaining nine months of 2018	8.9
2018	9.7
2019	7.7
2020	7.6
2021	6.8
Thereafter	7.1
Total	47.8
Future contractual minimum rental revenues
Remaining nine months of 2018	8.2
2018	8.2
2019	5.3
2020	3.8
2021	3.3
Thereafter	1.4
Total	$ 30.2