Debt - Remaining principal payments under existing debt agreements (Details) $ in Millions	Jun. 30, 2020 USD ($)
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	$ 96.7
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	211.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Three	655.4
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Four	323.1
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	2,814.4
Long-term Debt, Gross	4,859.7
Corporate Segment [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
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 [Member] | Secured Debt [Member] | 2009 Secured Railcar Equipment Notes [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	3.7
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	144.9
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | 2010 Secured Railcar Equipment Notes [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	9.9
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	152.1
Long-term Debt, Gross	243.8
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | 2018 Secured Railcar Equipment Notes [Domain]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	10.0
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	442.4
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | TRIHC 2018 Secured Railcar Equipment Notes [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	5.2
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	261.4
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | 2019 Secured Railcar Equipment Notes [Domain] [Domain]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	18.2
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	883.4
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | TRL 2012 Secured Railcar Equipment Notes - RIV 2013 [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	9.6
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	22.0
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	260.8
Long-term Debt, Gross	360.8
Railcar Leasing and Management Services Group [Member] | Secured Debt [Member] | TRIP Master Funding Secured Railcar Equipment Notes [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	15.9
Long-term Debt and Capital Lease Obligations, Maturities, Repayments of Principal in Year Two	40.5
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	900.9
Railcar Leasing and Management Services Group [Member] | Promissory Notes [Member] | 2017 Secured Railcar Equipment Notes [Member] [Domain]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	16.6
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	460.4
Long-term Debt, Gross	609.6
Railcar Leasing and Management Services Group [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | TILC Warehouse Facility [Member]
Long-term Debt, Fiscal Year Maturity [Abstract]
Long-term Debt, Maturities, Repayments of Principal, Remainder of Fiscal Year	7.6
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	25.4
Railcar Leasing and Management Services Group [Member] | Line of Credit [Member] | Revolving Credit Facility [Member] | Facility termination payments – TILC warehouse facility
Long-term Debt, Fiscal Year Maturity [Abstract]
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	457.1
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	$ 457.1