Fair Value Accounting - Carrying amounts and estimated fair values of long-term debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Gross	$ 400.0	$ 877.7
Less: unamortized discount		(8.5)
Less: unamortized debt issuance costs	(2.3)	(2.9)
Recourse, net of unamortized discount and unamortized debt issuance costs	397.4	866.3
Non-recourse debt	3,666.9	2,401.2
Less: unamortized debt issuance costs	(32.4)	(25.6)
Non-recourse debt, net of unamortized debt issuance costs	3,631.8	2,375.6
Total debt	4,029.2	3,241.9
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	399.7	869.2
Less: unamortized debt issuance costs	(2.3)	(2.9)
Recourse, net of unamortized discount and unamortized debt issuance costs	397.4	866.3
Non-recourse debt	3,664.2	2,401.2
Less: unamortized debt issuance costs	(32.4)	(25.6)
Non-recourse debt, net of unamortized debt issuance costs	3,631.8	2,375.6
Total debt	4,029.2	3,241.9
Carrying Value \| 2006 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	133.4	158.5
Carrying Value \| 2009 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	159.7	166.2
Carrying Value \| 2010 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	257.0	266.9
Carrying Value \| 2018 Secured Railcar Equipment Notes [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	472.2	0.0
Carrying Value \| TRIHC 2018 Secured Railcar Equipment Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	279.0	0.0
Carrying Value \| TRL 2012 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	386.2	402.8
Carrying Value \| TRIP Master Funding secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	941.7	962.5
Carrying Value \| Senior notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	399.7	399.7
Carrying Value \| Convertible subordinated notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	0.0	441.2
Long-term Debt, Gross	0.0	449.4
Less: unamortized discount	0.0	(8.2)
Carrying Value \| Capital lease obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	0.0	28.3
Carrying Value \| Line of credit \| TILC warehouse facility \| Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	374.8	150.7
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	343.7	1,143.6
Non-recourse debt	3,698.2	2,459.5
Total debt	4,041.9	3,603.1
Estimated Fair Value \| 2006 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	138.0	165.7
Estimated Fair Value \| 2009 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	174.0	169.6
Estimated Fair Value \| 2010 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	264.0	281.9
Estimated Fair Value \| 2017 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	660.2	293.6
Estimated Fair Value \| 2018 Secured Railcar Equipment Notes [Domain]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	475.2	0.0
Estimated Fair Value \| TRIHC 2018 Secured Railcar Equipment Notes [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	278.1	0.0
Estimated Fair Value \| TRL 2012 secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	370.9	390.4
Estimated Fair Value \| TRIP Master Funding secured railcar equipment notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	963.0	1,007.6
Estimated Fair Value \| Senior notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	343.7	400.3
Estimated Fair Value \| Convertible subordinated notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Gross	0.0	715.0
Estimated Fair Value \| Capital lease obligations
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including unamortized debt issuance costs, net of unamortized discount	0.0	28.3
Estimated Fair Value \| Line of credit \| TILC warehouse facility \| Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Non-recourse debt	$ 374.8	$ 150.7

Long-term Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs

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