Stock-Based Compensation - Schedule of restricted stock activity (Details) - Restricted share awards	12 Months Ended
Dec. 31, 2019 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Weighted Average Grant-Date Fair Value per Award, Equity awards outstanding, Beginning balance (in dollars per share) \| $ / shares	$ 21.12
Weighted Average Grant-Date Fair Value per Award, Granted (in dollars per share) \| $ / shares	36.21
Weighted Average Grant-Date Fair Value per Award, Vested (in dollars per share) \| $ / shares	20.17
Weighted Average Grant-Date Fair Value per Award, Forfeited (in dollars per share) \| $ / shares	25.60
Weighted Average Grant-Date Fair Value per Award, Equity awards outstanding, Ending balance (in dollars per share) \| $ / shares	$ 24.20
Trinity Equity Awards Held by Arcosa Employees
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Equity Awards, Restricted share awards outstanding, Beginning balance (in shares)	1,156,959
Number of Equity Awards, Granted (in shares)	0
Number of Equity Awards, Vested (in shares)	(293,239)
Number of Equity Awards, Forfeited (in shares)	(39,735)
Number of Equity Share Awards, Restricted share awards outstanding, Ending balance (in shares)	823,985
Arcosa Equity Awards Held by Arcosa Employees
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Number of Equity Awards, Restricted share awards outstanding, Beginning balance (in shares)	1,066,165
Number of Equity Awards, Granted (in shares)	417,008
Number of Equity Awards, Vested (in shares)	(198,762)
Number of Equity Awards, Forfeited (in shares)	(59,743)
Number of Equity Share Awards, Restricted share awards outstanding, Ending balance (in shares)	1,224,668

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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