Debt - Remaining principal payments under existing debt agreements (Details) $ in Millions	Mar. 31, 2019 USD ($)
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	$ 133.1
2020	184.6
2021	205.8
2022	739.6
2023	428.3
Thereafter	2,810.6
Corporate
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0.0
2020	0.0
2021	0.0
2022	0.0
2023	250.0
Thereafter	400.0
Railcar Leasing and Management Services Group | Secured Debt [Member] | 2006 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	21.8
2020	29.7
2021	29.1
2022	29.8
2023	16.1
Thereafter	0.0
Railcar Leasing and Management Services Group | Secured Debt [Member] | 2009 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	8.3
2020	6.6
2021	13.4
2022	14.0
2023	11.8
Thereafter	102.5
Railcar Leasing and Management Services Group | Secured Debt [Member] | 2010 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	6.0
2020	14.1
2021	20.0
2022	20.9
2023	22.5
Thereafter	171.1
Railcar Leasing and Management Services Group | Secured Debt [Member] | 2018 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	15.0
2020	20.0
2021	20.0
2022	20.0
2023	20.0
Thereafter	372.5
Railcar Leasing and Management Services Group | Secured Debt [Member] | TRIHC 2018 Secured Railcar Equipment Notes [Member]
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	9.8
2020	10.9
2021	11.9
2022	9.3
2023	11.6
Thereafter	223.5
Railcar Leasing and Management Services Group | Secured Debt [Member] | TRL 2012 secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	15.9
2020	19.3
2021	19.9
2022	19.6
2023	26.2
Thereafter	280.8
Railcar Leasing and Management Services Group | Secured Debt [Member] | TRIP Master Funding secured railcar equipment notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	17.9
2020	32.9
2021	40.4
2022	41.8
2023	37.0
Thereafter	765.7
Railcar Leasing and Management Services Group | Promissory note | 2017 promissory notes
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	24.9
2020	33.1
2021	33.1
2022	33.2
2023	33.1
Thereafter	494.5
Railcar Leasing and Management Services Group | Line of credit | Revolving credit facility | TILC warehouse facility
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	13.5
2020	18.0
2021	18.0
2022	3.0
2023	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
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	0.0
2020	0.0
2021	0.0
2022	548.0
2023	0.0
Thereafter	$ 0.0