Debt - Components of debt (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Total recourse debt	$ 448.4	$ 448.2
Non-Recourse Debt	4,839.8	4,568.8
Total debt	5,288.2	5,017.0
Level 1
Debt Instrument [Line Items]
Long-term Debt, Fair Value	1,695.2	1,372.1
Level 2
Debt Instrument [Line Items]
Long-term Debt, Fair Value	426.2	420.3
Level 3
Debt Instrument [Line Items]
Long-term Debt, Fair Value	3,313.7	3,462.4
Fair Value, Inputs, Level 1, 2 and 3
Debt Instrument [Line Items]
Long-term Debt, Fair Value	5,435.1	5,254.8
Corporate Segment [Member]
Debt Instrument [Line Items]
Long-term Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	449.8	449.8
Less: unamortized debt issuance costs	1.4	1.6
Senior Notes [Member] \| Corporate Segment [Member]
Debt Instrument [Line Items]
Long-term Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	399.8	399.8
Debt Instrument, Unamortized Discount	0.2	0.2
TRIP Railcar Co Term Loan \| Line of Credit [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
TILC warehouse facility	329.6	0.0
Wholly Owned Subsidiaries [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	3,607.3	3,340.5
Wholly Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Less: unamortized debt issuance costs	26.4	24.0
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	3,633.7	3,364.5
Non-Recourse Debt	3,607.3	3,340.5
Wholly Owned Subsidiaries [Member] \| Secured Debt [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount	0.5	0.6
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	2,318.1	2,042.4
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 Instrument, Unamortized Discount	9.0	10.1
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	781.4	802.7
Partially-Owned Subsidiaries [Member]
Debt Instrument [Line Items]
Non-Recourse Debt	1,232.5	1,228.3
Partially-Owned Subsidiaries [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Less: unamortized debt issuance costs	12.2	9.2
Non-Recourse Debt	1,232.5	1,228.3
Partially-Owned Subsidiaries [Member] \| Secured Debt [Member] \| Railcar Leasing and Management Services Group [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount	0.3	0.0
Non-Recourse Debt, Gross of Issuance Cost, Net of Discount	915.1	1,237.5
Revolving Credit Facility [Member] \| Line of Credit [Member] \| Corporate Segment [Member]
Debt Instrument [Line Items]
Long-term Debt, Net of Unamortized Discount, Gross of Unamortized Debt Issuance Costs	50.0	50.0
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]
TILC warehouse facility	$ 534.2	$ 519.4

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

No definition available.

Name:	trn_LongtermDebtNetofUnamortizedDiscountGrossofUnamortizedDebtIssuanceCosts
Namespace Prefix:	trn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Non-Recourse Debt, Gross of Issuance Cost, Net of Discount

+ References

No definition available.

+ Details

Name:	trn_NonRecourseDebtGrossofIssuanceCostNetofDiscount
Namespace Prefix:	trn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Recourse And Non-Recourse Debt And Capital Lease Obligations

+ References

No definition available.

+ Details

Name:	trn_RecourseAndNonRecourseDebtAndCapitalLeaseObligations
Namespace Prefix:	trn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of short-term and long-term debt and lease obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Name:	us-gaap_DebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28541-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of debt for which creditor does not have general recourse to the debtor but rather has recourse only to the property used for collateral in the transaction or other specific property.

+ References

No definition available.

+ Details

Name:	us-gaap_NonRecourseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel12And3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_CorporateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SeniorNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trn_TRIPRailcarCoTermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=trn_RailcarLeasingAndManagementServicesGroupMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=trn_WhollyOwnedSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trn_A2017SecuredRailcarEquipmentNotesMemberDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=trn_PromissoryNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=trn_PartiallyOwnedSubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=trn_TILCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=trn_TilcWarehouseFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: