Debt - Remaining principal payments under existing debt agreements (Details) $ in Millions	Sep. 30, 2017 USD ($)
Remaining principal payments under existing debt agreements
Remaining three months of 2017	$ 26.1
2018	135.2
2019	265.8
2020	118.1
2021	138.2
Thereafter	2,636.4
Corporate
Remaining principal payments under existing debt agreements
Remaining three months of 2017	0.0
2018	0.1
2019	0.1
2020	0.2
2021	0.1
Thereafter	849.4
Railcar Leasing and Management Services Group | Capital lease obligations
Remaining principal payments under existing debt agreements
Remaining three months of 2017	0.9
2018	28.5
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 three months of 2017	6.1
2018	25.3
2019	28.0
2020	29.8
2021	29.2
Thereafter	46.0
Railcar Leasing and Management Services Group | Secured debt | 2009 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining three months of 2017	1.6
2018	6.4
2019	11.2
2020	6.6
2021	13.4
Thereafter	128.5
Railcar Leasing and Management Services Group | Secured debt | 2010 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining three months of 2017	2.9
2018	10.0
2019	7.6
2020	14.2
2021	20.1
Thereafter	215.1
Railcar Leasing and Management Services Group | Secured debt | TRL 2012 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining three months of 2017	5.5
2018	22.9
2019	21.9
2020	19.3
2021	19.9
Thereafter	318.7
Railcar Leasing and Management Services Group | Secured debt | TRIP Master Funding secured railcar equipment notes
Remaining principal payments under existing debt agreements
Remaining three months of 2017	3.6
2018	20.0
2019	23.8
2020	32.9
2021	40.4
Thereafter	845.5
Railcar Leasing and Management Services Group | Promissory note | 2017 promissory notes
Remaining principal payments under existing debt agreements
Remaining three months of 2017	3.8
2018	15.1
2019	15.1
2020	15.1
2021	15.1
Thereafter	233.2
Railcar Leasing and Management Services Group | Line of credit | Revolving credit facility | TILC warehouse facility
Remaining principal payments under existing debt agreements
Remaining three months of 2017	1.7
2018	6.9
2019	1.7
2020	0.0
2021	0.0
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 three months of 2017	0.0
2018	0.0
2019	156.4
2020	0.0
2021	0.0
Thereafter	$ 0.0