Debt - Remaining principal payments under existing debt agreements (Details) $ in Millions	Mar. 31, 2020 USD ($)
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 142.7
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	211.8
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	657.1
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	323.6
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	758.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	2,813.2
Long-term Debt, Gross	4,906.6
Corporate
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	130.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	400.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	0.0
Long-term Debt, Gross	530.0
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, Remainder of Fiscal Year	5.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	13.4
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	14.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	11.7
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	14.5
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	87.6
Long-term Debt, Gross	146.2
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, Remainder of Fiscal Year	12.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	20.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	20.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	22.4
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	18.5
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	152.2
Long-term Debt, Gross	246.2
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, Remainder of Fiscal Year	15.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	20.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	20.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	20.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	20.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	352.4
Long-term Debt, Gross	447.4
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, Remainder of Fiscal Year	7.5
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	11.8
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	9.3
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	11.7
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	14.7
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	208.7
Long-term Debt, Gross	263.7
Railcar Leasing and Management Services Group | Secured Debt [Member] | 2019 Secured Railcar Equipment Notes [Domain] [Domain]
Remaining principal payments under existing debt agreements
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	27.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	38.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	37.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	35.1
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	36.8
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	718.3
Long-term Debt, Gross	892.4
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, Remainder of Fiscal Year	14.5
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	19.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	19.6
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	22.5
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	28.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	258.6
Long-term Debt, Gross	364.0
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, Remainder of Fiscal Year	25.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	40.4
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	41.8
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	37.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	191.6
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	574.1
Long-term Debt, Gross	909.9
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, Remainder of Fiscal Year	24.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	33.1
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	33.1
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	33.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	33.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	461.3
Long-term Debt, Gross	618.8
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, Remainder of Fiscal Year	11.4
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	15.2
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	2.6
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	0.0
Long-term Debt, Gross	29.2
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, Remainder of Fiscal Year	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	458.8
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Five	0.0
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal after Year Five	0.0
Long-term Debt, Gross	$ 458.8