Note 13. Common Stock and Stock-based Compensation Stock Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2023		Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		22,050,000
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant		3,221,792
Stock-based compensation expense		$ 22.7		$ 22.5	$ 20.7
Share-based Payment Arrangement, Expense, Tax Benefit		$ 2.8		$ 2.6	$ 10.7
Share-based Payment Arrangement, Option, Exercise Price Range, Outstanding, Weighted Average Exercise Price		$ 21.61
Restricted Shares Outstanding, Converted		$ 0.2
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Period Increase (Decrease)		300,000		300,000
Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price		$ 5.26		$ 5.26
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price		$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period		0
Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price		$ 0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period		0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price		$ 0
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number		300,000
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price		$ 5.26
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term		6 years 1 month 6 days
Share-Based Payment Arrangement, Option, Exercise Price Range, Exercisable, Weighted Average Remaining Contractual Term		6 years 1 month 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value		$ 1.5
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value		1.5
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		0.0
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 17.2
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		1 year 7 months 6 days
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number		1,646,571		1,740,166
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value		$ 22.60		$ 23.20
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		636,258
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 21.63		$ 25.65	$ 28.41
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period		645,604
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value		$ 23.09
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures		(84,249)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value		$ 24.05
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 14.9		$ 14.2	$ 21.1
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 7.8
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		1 year 4 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number		747,214		921,391
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value		$ 29.41		$ 25.56
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		284,061
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 27.72		$ 29.80	$ 30.85
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Period Increase (Decrease)	[1]	27,299
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Period Increase (Decrease), Weighted Average Grant Date Fair Value		$ 20.05
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	[2]	412,827
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value		$ 24.71
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures		(18,112)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value		$ 28.23
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 10.2		$ 4.7	$ 7.2
Performance Shares [Member] | Return on Equity
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Period Increase (Decrease)		221,509
Performance Shares [Member] | Relative Total Shareholder Return (rTSR)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Period Increase (Decrease)		(194,210)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period		194,210
Restricted Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount		$ 2.0
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition		3 years 10 months 24 days
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number		552,240	[3]	655,050
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value		$ 20.84		$ 21.07
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period		22,937
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value		$ 21.32		$ 25.43	$ 28.48
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period		94,630
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value		$ 20.91
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures		(31,117)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value		$ 25.93
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value		$ 2.0		$ 1.7	$ 4.1
Minimum [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Maximum [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years

[1] For the 2020-2022 performance period, performance adjustment includes 221,509 performance units for return on equity, for which actual performance was below the minimum established threshold and thus resulted in no payout, and is net of 194,210 additional performance units for relative total shareholder return, for which actual performance resulted in a payout of 200% of target.

[2] Includes 194,210 performance units for the 2020-2022 performance period for relative total shareholder return that were paid out at 200% of target based on actual performance achieved.

[3] The balance of RSAs outstanding at December 31, 2023 includes approximately 0.2 million RSAs for Arcosa Inc. ("Arcosa") employees that were converted under the shareholder method at the time of the Arcosa spin-off. These RSAs will be released to Arcosa employees upon vesting, but as of the spin-off date, Trinity no longer records the compensation expense associated with these shares.