Debt - Components of debt (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Debt:	$ 5,832.6	$ 5,607.6
Recourse
Debt Instrument [Line Items]
Debt:	793.9	624.1
Nonrecourse
Debt Instrument [Line Items]
Debt:	5,038.7	4,983.5
Level 1
Debt Instrument [Line Items]
Long-term Debt, Fair Value	1,580.4	1,662.8
Level 2
Debt Instrument [Line Items]
Long-term Debt, Fair Value	796.6	387.5
Level 3
Debt Instrument [Line Items]
Long-term Debt, Fair Value	3,116.5	3,194.0
Fair Value, Inputs, Level 1, 2 and 3
Debt Instrument [Line Items]
Long-term Debt, Fair Value	5,493.5	5,244.3
Corporate Segment [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	799.9	624.9
Less: unamortized debt issuance costs	6.0	0.8
Senior Notes due 2024 \| Corporate Segment [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	399.9	399.9
Debt Instrument, Unamortized Discount	0.1	0.1
Senior Notes due 2028 \| Corporate Segment [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	400.0	0.0
Wholly Owned Subsidiaries [Member] \| Nonrecourse
Debt Instrument [Line Items]
Debt:	3,870.8	3,800.7
Wholly Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	3,891.2	3,821.8
Less: unamortized debt issuance costs	20.4	21.1
Wholly Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member] \| Nonrecourse
Debt Instrument [Line Items]
Debt:	3,870.8	3,800.7
Wholly Owned Subsidiaries [Member] \| Secured Debt [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	2,310.8	2,384.0
Debt Instrument, Unamortized Discount	0.3	0.3
Wholly Owned Subsidiaries [Member] \| 2017 Secured Railcar Equipment Notes [Member] [Domain] \| Promissory Notes [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	694.9	716.0
Debt Instrument, Unamortized Discount	4.5	5.6
Wholly Owned Subsidiaries [Member] \| TRL-2023 Term Loan \| Line of Credit [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	340.0	0.0
Partially-Owned Subsidiaries [Member] \| Nonrecourse
Debt Instrument [Line Items]
Debt:	1,167.9	1,182.8
Partially-Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Less: unamortized debt issuance costs	8.6	9.8
Partially-Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member] \| Nonrecourse
Debt Instrument [Line Items]
Debt:	1,167.9	1,182.8
Partially-Owned Subsidiaries [Member] \| Secured Debt [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	1,176.5	1,192.6
Debt Instrument, Unamortized Discount	0.2	0.3
Revolving Credit Facility [Member] \| Line of Credit [Member] \| Corporate Segment [Member]
Debt Instrument [Line Items]
Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	0.0	225.0
Revolving Credit Facility [Member] \| TILC [Member] \| TILC Warehouse Facility [Member] \| Line of Credit [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Long-term Line of Credit	$ 545.5	$ 721.8

Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

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- Definition

Amount, after accumulated amortization, of debt discount.

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+ Details

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Balance Type:	debit
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- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

No definition available.

+ Details

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Period Type:	instant

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

No definition available.

+ Details

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