Summary of Significant Accounting Policies (Policies)	6 Months Ended
Jun. 30, 2026
Accounting Policies [Abstract]
Consolidation, Policy [Policy Text Block]	Basis of Presentation The foregoing Consolidated Financial Statements are unaudited and have been prepared from the books and records of Trinity Industries, Inc. and Subsidiaries (“Trinity,” “Company,” “we,” “our,” or "us"), which include the accounts of our wholly-owned subsidiaries and Trinity Global Ventures Limited ("Trinity Global Ventures"), a partially-owned subsidiary in which we have a controlling interest. Previously, TRIP Rail Holdings LLC ("TRIP Holdings") was a partially-owned subsidiary in the Leasing Group. In April 2026, the Leasing Group fully divested its ownership in TRIP Holdings through a railcar partnership transaction as further described in Note 5. In our opinion, all normal and recurring adjustments necessary for a fair presentation of our financial position as of June 30, 2026, the results of operations for the three and six months ended June 30, 2026 and 2025, and cash flows for the six months ended June 30, 2026 have been made in conformity with generally accepted accounting principles. All significant intercompany accounts and transactions have been eliminated. Certain prior year balances have been reclassified to conform to the 2026 presentation. Due to seasonal and other factors, the results of operations for the six months ended June 30, 2026 may not be indicative of expected results of operations for the year ending December 31, 2026. These interim financial statements and notes are condensed as permitted by the instructions to Form 10-Q and should be read in conjunction with our audited Consolidated Financial Statements included in our Form 10-K for the year ended December 31, 2025. There have been no changes to our significant accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2025 that had a material impact on our Consolidated Financial Statements or related notes as of and for the three and six months ended June 30, 2026.
Cash and Cash Equivalents, Policy [Policy Text Block]	Financial Instruments We consider all highly liquid debt instruments to be either cash and cash equivalents if purchased with a maturity of three months or less, or short-term marketable securities if purchased with a maturity of more than three months and less than one year. Financial instruments that potentially subject us to a concentration of credit risk are primarily cash investments, including restricted cash and receivables. We place our cash investments in bank deposits, investment grade short-term debt instruments, highly-rated money market funds, and highly-rated commercial paper. We limit the amount of credit exposure to any one commercial issuer. The carrying values of cash, receivables, and accounts payable are considered to be representative of their respective fair values. Concentrations of credit risk with respect to receivables are limited due to control procedures that monitor the credit worthiness of customers, the large number of customers in our customer base, and their dispersion across different end markets and geographic areas. Receivables are generally evaluated at a portfolio level based on these characteristics. As receivables are generally unsecured, we maintain an allowance for credit losses using a forward-looking approach based on historical losses and consideration of current and expected future economic conditions. Historically, we have observed that the likelihood of loss increases when receivables have aged beyond 180 days or when we become aware that a customer has experienced a deterioration in their financial condition. When a receivable is deemed uncollectible, the write-off is recorded as a reduction to the allowance for credit losses. During the six months ended June 30, 2026, we recognized approximately $1.9 million of credit loss expense and approximately $0.4 million of recoveries and other adjustments, and wrote off $3.7 million related to our trade receivables that are in the scope of Accounting Standards Codification ("ASC") 326, Financial Instruments – Credit Losses, bringing the allowance for credit losses balance from $23.6 million at December 31, 2025 to $21.4 million at June 30, 2026. This balance excludes the general reserve for operating lease receivables that is permitted under ASC 450, Contingencies.
Supplier Finance Program	Supply Chain Finance Program In cooperation with a participating financial institution, we facilitate a voluntary supply chain finance ("SCF") program for several of our suppliers. We negotiate payment terms with suppliers that are in line with average industry terms. We have not pledged any assets as security or provided other forms of guarantees to the financial institution. Under the SCF program, participating suppliers may choose to sell, at a discounted price, receivables due from us to the financial institution, at the sole discretion of both the suppliers and the financial institution, prior to the invoices’ scheduled due dates. The payment terms that we negotiate with all suppliers are consistent regardless of whether the supplier chooses to participate in the SCF program for a particular invoice. The SCF program is administered by a third-party financial institution, and our responsibility is limited to making payments based on the terms originally negotiated with participating suppliers, regardless of whether such suppliers sell receivables to the financial institution. Amounts due to our participating suppliers in the SCF program totaled $49.6 million and $49.1 million as of June 30, 2026 and December 31, 2025, respectively, and are included in accounts payable in our Consolidated Balance Sheets. Payments made under the SCF program are reflected in net cash provided by operating activities from continuing operations in our Consolidated Statements of Cash Flows.
Discontinued Operations, Policy	Discontinued Operations In the fourth quarter of 2021, we completed the sale of Trinity Highway Products, LLC (“THP”). Upon completion of the sale, the accounting requirements for reporting THP as a discontinued operation were met. In connection with the sale, the Company agreed to indemnify the buyer for certain liabilities related to the highway products business, including certain liabilities resulting from or arising out of the ET-Plus® System, a highway guardrail end-terminal system (the “ET Plus”). Consequently, results from discontinued operations include certain legal expenses that are directly attributable to the highway products business. Similar expenses related to these retained obligations that may be incurred in the future will likewise be reported in discontinued operations. For the three and six months ended June 30, 2026, we recorded expenses related to these obligations of $5.0 million ($3.9 million, net of income taxes) and $7.4 million ($5.7 million, net of income taxes), respectively. For the three and six months ended June 30, 2025, we recorded expenses related to these obligations of $2.4 million ($1.9 million, net of income taxes) and $4.9 million ($3.8 million, net of income taxes), respectively. These expenses are included in loss from discontinued operations, net of income taxes in our Consolidated Statements of Operations. See Note 15 of our Annual Report on Form 10-K for further information regarding obligations retained in connection with the THP sale.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements Not Yet Adopted ASU 2024-03 – In November 2024, the FASB issued ASU No. 2024-03, "Disaggregation of Income Statement Expenses," which improves financial reporting and responds to investor input by requiring public companies to disclose additional information about certain expenses in the notes to the consolidated financial statements. ASU 2024-03 requires disclosures, on an annual and interim basis, of the amounts of purchases of inventory, employee compensation, depreciation, and intangible asset amortization included in each relevant expense category; a qualitative description of amounts remaining that are not separately disaggregated quantitatively; and the amount of selling expenses and, in annual reporting periods, the definition of selling expenses. ASU 2024-03 is effective for public companies during annual reporting periods beginning after December 15, 2026 on a prospective basis, with an option for retrospective application. Early adoption is permitted. We are currently evaluating the impact ASU 2024-03 will have on our financial statement disclosures. ASU 2025-06 – In September 2025, the FASB issued ASU No. 2025-06, "Targeted Improvements to the Accounting for Internal-Use Software," which modernizes the accounting for internal-use software costs by removing all references to prescriptive and sequential software development stages. Under this guidance, capitalization of eligible costs begins when management has authorized and committed to funding the software project and it is probable the project will be completed and the software will be used for the function intended. ASU 2025-06 is effective for public companies during the annual reporting periods beginning after December 15, 2027 using a prospective approach, modified transition approach for in-process projects, or a retrospective approach. Early adoption is permitted. We are currently evaluating the impact ASU 2025-06 will have on our Consolidated Financial Statements.

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2026

Consolidation, Policy [Policy Text Block]

Basis of Presentation

The foregoing Consolidated Financial Statements are unaudited and have been prepared from the books and records of Trinity Industries, Inc. and Subsidiaries (“Trinity,” “Company,” “we,” “our,” or "us"), which include the accounts of our wholly-owned subsidiaries and Trinity Global Ventures Limited ("Trinity Global Ventures"), a partially-owned subsidiary in which we have a controlling interest. Previously, TRIP Rail Holdings LLC ("TRIP Holdings") was a partially-owned subsidiary in the Leasing Group. In April 2026, the Leasing Group fully divested its ownership in TRIP Holdings through a railcar partnership transaction as further described in Note 5. In our opinion, all normal and recurring adjustments necessary for a fair presentation of our financial position as of June 30, 2026, the results of operations for the three and six months ended June 30, 2026 and 2025, and cash flows for the six months ended June 30, 2026 have been made in conformity with generally accepted accounting principles. All significant intercompany accounts and transactions have been eliminated. Certain prior year balances have been reclassified to conform to the 2026 presentation.

Due to seasonal and other factors, the results of operations for the six months ended June 30, 2026 may not be indicative of expected results of operations for the year ending December 31, 2026. These interim financial statements and notes are condensed as permitted by the instructions to Form 10-Q and should be read in conjunction with our audited Consolidated Financial Statements included in our Form 10-K for the year ended December 31, 2025. There have been no changes to our significant accounting policies disclosed in our Annual Report on Form 10-K for the year ended December 31, 2025 that had a material impact on our Consolidated Financial Statements or related notes as of and for the three and six months ended June 30, 2026.

Cash and Cash Equivalents, Policy [Policy Text Block]

Financial Instruments

We consider all highly liquid debt instruments to be either cash and cash equivalents if purchased with a maturity of three months or less, or short-term marketable securities if purchased with a maturity of more than three months and less than one year.

Financial instruments that potentially subject us to a concentration of credit risk are primarily cash investments, including restricted cash and receivables. We place our cash investments in bank deposits, investment grade short-term debt instruments, highly-rated money market funds, and highly-rated commercial paper. We limit the amount of credit exposure to any one commercial issuer. The carrying values of cash, receivables, and accounts payable are considered to be representative of their respective fair values.

Concentrations of credit risk with respect to receivables are limited due to control procedures that monitor the credit worthiness of customers, the large number of customers in our customer base, and their dispersion across different end markets and geographic areas. Receivables are generally evaluated at a portfolio level based on these characteristics. As receivables are generally unsecured, we maintain an allowance for credit losses using a forward-looking approach based on historical losses and consideration of current and expected future economic conditions. Historically, we have observed that the likelihood of loss increases when receivables have aged beyond 180 days or when we become aware that a customer has experienced a deterioration in their financial condition. When a receivable is deemed uncollectible, the write-off is recorded as a reduction to the allowance for credit losses. During the six months ended June 30, 2026, we recognized approximately $1.9 million of credit loss expense and approximately $0.4 million of recoveries and other adjustments, and wrote off $3.7 million related to our trade receivables that are in the scope of Accounting Standards Codification ("ASC") 326, Financial Instruments – Credit Losses, bringing the allowance for credit losses balance from $23.6 million at December 31, 2025 to $21.4 million at June 30, 2026. This balance excludes the general reserve for operating lease receivables that is permitted under ASC 450, Contingencies.

Supplier Finance Program

Supply Chain Finance Program

In cooperation with a participating financial institution, we facilitate a voluntary supply chain finance ("SCF") program for several of our suppliers. We negotiate payment terms with suppliers that are in line with average industry terms. We have not pledged any assets as security or provided other forms of guarantees to the financial institution. Under the SCF program, participating suppliers may choose to sell, at a discounted price, receivables due from us to the financial institution, at the sole discretion of both the suppliers and the financial institution, prior to the invoices’ scheduled due dates. The payment terms that we negotiate with all suppliers are consistent regardless of whether the supplier chooses to participate in the SCF program for a particular invoice. The SCF program is administered by a third-party financial institution, and our responsibility is limited to making payments based on the terms originally negotiated with participating suppliers, regardless of whether such suppliers sell receivables to the financial institution.

Amounts due to our participating suppliers in the SCF program totaled $49.6 million and $49.1 million as of June 30, 2026 and December 31, 2025, respectively, and are included in accounts payable in our Consolidated Balance Sheets. Payments made under the SCF program are reflected in net cash provided by operating activities from continuing operations in our Consolidated Statements of Cash Flows.

Discontinued Operations, Policy

Discontinued Operations

In the fourth quarter of 2021, we completed the sale of Trinity Highway Products, LLC (“THP”). Upon completion of the sale, the accounting requirements for reporting THP as a discontinued operation were met. In connection with the sale, the Company agreed to indemnify the buyer for certain liabilities related to the highway products business, including certain liabilities resulting from or arising out of the ET-Plus® System, a highway guardrail end-terminal system (the “ET Plus”). Consequently, results from discontinued operations include certain legal expenses that are directly attributable to the highway products business. Similar expenses related to these retained obligations that may be incurred in the future will likewise be reported in discontinued operations. For the three and six months ended June 30, 2026, we recorded expenses related to these obligations of $5.0 million ($3.9 million, net of income taxes) and $7.4 million ($5.7 million, net of income taxes), respectively. For the three and six months ended June 30, 2025, we recorded expenses related to these obligations of $2.4 million ($1.9 million, net of income taxes) and $4.9 million ($3.8 million, net of income taxes), respectively. These expenses are included in loss from discontinued operations, net of income taxes in our Consolidated Statements of Operations. See Note 15 of our Annual Report on Form 10-K for further information regarding obligations retained in connection with the THP sale.

New Accounting Pronouncements, Policy [Policy Text Block]

Recent Accounting Pronouncements

Not Yet Adopted

ASU 2024-03 – In November 2024, the FASB issued ASU No. 2024-03, "Disaggregation of Income Statement Expenses," which improves financial reporting and responds to investor input by requiring public companies to disclose additional information about certain expenses in the notes to the consolidated financial statements. ASU 2024-03 requires disclosures, on an annual and interim basis, of the amounts of purchases of inventory, employee compensation, depreciation, and intangible asset amortization included in each relevant expense category; a qualitative description of amounts remaining that are not separately disaggregated quantitatively; and the amount of selling expenses and, in annual reporting periods, the definition of selling expenses. ASU 2024-03 is effective for public companies during annual reporting periods beginning after December 15, 2026 on a prospective basis, with an option for retrospective application. Early adoption is permitted. We are currently evaluating the impact ASU 2024-03 will have on our financial statement disclosures.

ASU 2025-06 – In September 2025, the FASB issued ASU No. 2025-06, "Targeted Improvements to the Accounting for Internal-Use Software," which modernizes the accounting for internal-use software costs by removing all references to prescriptive and sequential software development stages. Under this guidance, capitalization of eligible costs begins when management has authorized and committed to funding the software project and it is probable the project will be completed and the software will be used for the function intended. ASU 2025-06 is effective for public companies during the annual reporting periods beginning after December 15, 2027 using a prospective approach, modified transition approach for in-process projects, or a retrospective approach. Early adoption is permitted. We are currently evaluating the impact ASU 2025-06 will have on our Consolidated Financial Statements.