Debt - Remaining principal payments under existing debt agreements (Details) $ in Millions	Jun. 30, 2018 USD ($)
Remaining principal payments under existing debt agreements
Remaining six months of 2018	$ 65.7
2018	158.7
2019	144.2
2020	164.2
2021	291.2
Thereafter	2,438.3
Corporate
Remaining principal payments under existing debt agreements
Remaining six months of 2018	0.1
2018	0.1
2019	0.2
2020	0.0
2021	0.0
Thereafter	400.0
Railcar Leasing and Management Services Group | Capital lease obligations
Remaining principal payments under existing debt agreements
Remaining six months of 2018	1.9
2018	24.9
2019	0.0
2020	0.0
2021	0.0
Thereafter	0.0
Railcar Leasing and Management Services Group | Secured debt | 2006 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	13.9
2018	28.0
2019	29.8
2020	29.2
2021	29.9
Thereafter	16.2
Railcar Leasing and Management Services Group | Secured debt | 2009 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	3.6
2018	11.2
2019	6.6
2020	13.4
2021	14.1
Thereafter	114.4
Railcar Leasing and Management Services Group | Secured debt | 2010 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	4.7
2018	7.6
2019	14.2
2020	20.1
2021	21.0
Thereafter	194.1
Railcar Leasing and Management Services Group | Secured debt | 2018 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	10.0
2018	20.0
2019	20.0
2020	20.0
2021	20.0
Thereafter	392.5
Railcar Leasing and Management Services Group | Secured debt | TRL 2012 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	11.8
2018	21.9
2019	19.3
2020	19.9
2021	19.6
Thereafter	299.8
Railcar Leasing and Management Services Group | Secured debt | TRIP Master Funding secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	9.0
2018	23.8
2019	32.9
2020	40.4
2021	41.8
Thereafter	803.3
Railcar Leasing and Management Services Group | Promissory note | 2017 promissory notes
Remaining principal payments under existing debt agreements
Remaining six months of 2018	7.6
2018	15.1
2019	15.1
2020	15.1
2021	15.1
Thereafter	218.0
Railcar Leasing and Management Services Group | Line of credit | Revolving credit facility | TILC warehouse facility
Remaining principal payments under existing debt agreements
Remaining six months of 2018	3.1
2018	6.1
2019	6.1
2020	6.1
2021	1.5
Thereafter	0.0
Railcar Leasing and Management Services Group | Line of credit | Revolving credit facility | Facility termination payments - TILC warehouse facility
Remaining principal payments under existing debt agreements
Remaining six months of 2018	0.0
2018	0.0
2019	0.0
2020	0.0
2021	128.2
Thereafter	$ 0.0