Note 10. Employee Retirement Plans Accumulated Benefit Obligations and Funded Status (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Retirement Benefits [Abstract]
Accumulated Benefit Obligations	$ 15.5	$ 557.9
Defined Benefit Plan, Benefit Obligation	15.5	557.9	$ 453.2
Service cost	0.0	0.1	0.1
Interest	14.8	19.7	18.3
Benefits paid	(23.0)	(22.2)
Actuarial (gain) loss	18.0	105.6
Plan amendments	0.0	1.5
Settlements	(552.2)	0.0
Defined Benefit Plan, Plan Assets, Amount	23.6	548.5	$ 478.7
Actual return on assets	49.3	90.9
Employer contributions	1.0	1.1
Benefits paid	(23.0)	(22.2)
Settlements	(552.2)	0.0
Trinity Industries, Inc. Consolidated Pension Plan [Member]
Defined Benefit Plan, Plan Assets, Category [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	23.6	5.5
Liability, Defined Benefit Plan	0.0	0.0
Defined Benefit Plan, Funded (Unfunded) Status of Plan	23.6	5.5
Supplemental Executive Retirement Plan (SERP) [Member]
Defined Benefit Plan, Plan Assets, Category [Line Items]
Assets for Plan Benefits, Defined Benefit Plan	0.0	0.0
Liability, Defined Benefit Plan	(15.5)	(14.9)
Defined Benefit Plan, Funded (Unfunded) Status of Plan	$ (15.5)	$ (14.9)