Railcar Leasing and Management Services Group - Future operating lease obligations and future contractual minimum rental revenues (Details) $ in Millions	Mar. 31, 2021 USD ($)
Future contractual minimum rental revenues
Total operating lease payments	$ 132.1
Railcar Leasing and Management Services Group [Member]
Future operating lease obligations
Remaining nine months of 2021	7.3
2022	9.0
2023	7.2
2024	3.9
2025	2.1
Thereafter	3.5
Total	33.0
Future contractual minimum rental revenues
Total operating lease payments	35.0
Railcar Leasing and Management Services Group [Member] | Building [Member]
Future contractual minimum rental revenues
Total operating lease payments	2.0
Railcar Leasing and Management Services Group [Member] | Property Lease Guarantee [Member]
Future contractual minimum rental revenues
Guarantor Obligations, Maximum Exposure, Undiscounted	1.9
Railcar Leasing and Management Services Group [Member] | Operating leases
Future contractual minimum rental revenues
Remaining nine months of 2021	4.3
2022	3.9
2023	1.9
2024	1.0
2025	0.3
Thereafter	0.2
Total	$ 11.6