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, 2022		Sep. 30, 2022		Jun. 30, 2022		Mar. 31, 2022		Dec. 31, 2021		Sep. 30, 2021		Jun. 30, 2021		Mar. 31, 2021		Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income (loss) from continuing operations	$ 42.8		$ 29.7		$ 16.5		$ 9.9		$ 21.6		$ 25.5		$ (2.8)		$ (5.0)		$ 98.9	$ 39.3	$ (250.5)
Less: Net (income) loss attributable to noncontrolling interest	(4.9)		(0.5)		(4.8)		(2.6)		(5.8)		(3.9)		7.9		2.0		(12.8)	0.2	78.9
Net income (loss) from continuing operations attributable to Trinity Industries, Inc.																	86.1	39.5	(171.6)
Income (loss) from discontinued operations, net of provision (benefit) for income taxes of $(1.1), $3.5, and $5.5	(6.6)		(3.4)		(3.4)		(6.9)		(13.2)		10.4		7.6		6.3		(20.3)	11.1	24.3
Gain (loss) on sale of discontinued operations, net of provision (benefit) for income taxes of $(1.4), $51.9, and $—	$ 0.0		$ 0.0		$ (4.6)		$ (1.1)		$ 131.4		$ 0.0		$ 0.0		$ 0.0		(5.7)	131.4	0.0
Net income (loss) from discontinued operations attributable to Trinity Industries, Inc.																	(26.0)	142.5	24.3
Net income (loss) attributable to Trinity Industries, Inc.																	$ 60.1	$ 182.0	$ (147.3)
Basic weighted average shares outstanding																	81.9	101.5	115.9
Effect of dilutive securities																	2.3	2.3	0.0
Diluted weighted average shares outstanding																	84.2	103.8	115.9
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.47	[1]	$ 0.36	[1]	$ 0.14	[1]	$ 0.09	[1]	$ 0.16	[1]	$ 0.22	[1]	$ 0.05	[1]	$ (0.03)	[1]	$ 1.05	$ 0.39	$ (1.48)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	(0.08)	[1]	(0.04)	[1]	(0.10)	[1]	(0.10)	[1]	1.23	[1]	0.11	[1]	0.07	[1]	0.06	[1]	(0.32)	1.40	0.21
Earnings Per Share, Basic	0.39	[1]	0.32	[1]	0.04	[1]	(0.01)	[1]	1.39	[1]	0.33	[1]	0.12	[1]	0.03	[1]	0.73	1.79	(1.27)
Income (Loss) from Continuing Operations, Per Diluted Share	0.46	[1]	0.35	[1]	0.14	[1]	0.09	[1]	0.16	[1]	0.22	[1]	0.05	[1]	(0.03)	[1]	1.02	0.38	(1.48)
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	(0.08)	[1]	(0.04)	[1]	(0.10)	[1]	(0.10)	[1]	1.21	[1]	0.11	[1]	0.07	[1]	0.06	[1]	(0.31)	1.37	0.21
Earnings Per Share, Diluted	$ 0.38	[1]	$ 0.31	[1]	$ 0.04	[1]	$ (0.01)	[1]	$ 1.37	[1]	$ 0.33	[1]	$ 0.12	[1]	$ 0.03	[1]	$ 0.71	$ 1.75	$ (1.27)
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																	0.1	0.1	0.0
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.