Note 14. Earnings Per Common Share Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2024		Sep. 30, 2024		Jun. 30, 2024		Mar. 31, 2024		Dec. 31, 2023		Sep. 30, 2023		Jun. 30, 2023		Mar. 31, 2023		Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income from continuing operations	$ 40.8		$ 40.8		$ 58.1		$ 31.7		$ 73.4		$ 26.3		$ 23.5		$ 16.8		$ 171.4	$ 140.0	$ 98.9
Less: Net income attributable to noncontrolling interest	(8.9)		(4.1)		(2.0)		(3.7)		(5.3)		(1.8)		(4.2)		(9.3)		(18.7)	(20.6)	(12.8)
Net income from continuing operations attributable to Trinity Industries, Inc.																	152.7	119.4	86.1
Loss from discontinued operations, net of benefit for income taxes of $4.1, $3.6, and $1.1	$ (3.0)		$ (5.3)		$ (1.7)		$ (4.3)		$ (5.3)		$ (2.7)		$ (2.3)		$ (3.1)		(14.3)	(13.4)	(20.3)
Loss on sale of discontinued operations, net of benefit for income taxes of $—, $—, and $1.4																	0.0	0.0	(5.7)
Net loss from discontinued operations attributable to Trinity Industries, Inc.																	(14.3)	(13.4)	(26.0)
Net income attributable to Trinity Industries, Inc.																	$ 138.4	$ 106.0	$ 60.1
Basic weighted average shares outstanding																	81.9	81.2	81.9
Effect of dilutive securities																	2.3	2.2	2.3
Diluted weighted average shares outstanding																	84.2	83.4	84.2
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.39	[1]	$ 0.45	[1]	$ 0.68	[1]	$ 0.34	[1]	$ 0.83	[1]	$ 0.30	[1]	$ 0.24	[1]	$ 0.09	[1]	$ 1.86	$ 1.47	$ 1.05
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	(0.04)	[1]	(0.07)	[1]	(0.02)	[1]	(0.05)	[1]	(0.06)	[1]	(0.03)	[1]	(0.03)	[1]	(0.04)	[1]	(0.17)	(0.16)	(0.32)
Earnings Per Share, Basic	0.35	[1]	0.38	[1]	0.66	[1]	0.29	[1]	0.77	[1]	0.27	[1]	0.21	[1]	0.05	[1]	1.69	1.31	0.73
Income (Loss) from Continuing Operations, Per Diluted Share	0.38	[1]	0.44	[1]	0.67	[1]	0.33	[1]	0.81	[1]	0.29	[1]	0.23	[1]	0.09	[1]	1.81	1.43	1.02
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	(0.04)	[1]	(0.07)	[1]	(0.02)	[1]	(0.05)	[1]	(0.06)	[1]	(0.03)	[1]	(0.03)	[1]	(0.04)	[1]	(0.17)	(0.16)	(0.31)
Earnings Per Share, Diluted	$ 0.34	[1]	$ 0.37	[1]	$ 0.65	[1]	$ 0.28	[1]	$ 0.75	[1]	$ 0.26	[1]	$ 0.20	[1]	$ 0.05	[1]	$ 1.64	$ 1.27	$ 0.71
Restricted Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	0.0	0.1	0.1
Share-based Payment Arrangement, Option [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	0.0	0.0	0.0

[1] The sum of the quarters may not necessarily be equal to the full year net income per common share amount.