Earnings Per Common Share - EPS calculation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income (loss) from continuing operations	$ 16.5	$ (2.8)	$ 26.4	$ (7.8)
Less: Net (income) loss attributable to noncontrolling interest	(4.8)	7.9	(7.4)	9.9
Net income from continuing operations attributable to Trinity Industries, Inc.	11.7	5.1	19.0	2.1
Income (loss) from discontinued operations, net of provision (benefit) for income taxes of $(0.5), $2.1, $(2.5), and $4.4	(3.4)	7.6	(10.3)	13.9
Loss on sale of discontinued operations, net of benefit for income taxes of $1.0, $—, $1.4, and $—	(4.6)	0.0	(5.7)	0.0
Net income (loss) from discontinued operations attributable to Trinity Industries, Inc.	(8.0)	7.6	(16.0)	13.9
Net income attributable to Trinity Industries, Inc.	$ 3.7	$ 12.7	$ 3.0	$ 16.0
Basic weighted average shares outstanding	82.4	102.8	82.7	106.4
Effect of dilutive securities	2.0	2.3	2.2	2.5
Diluted weighted average shares outstanding	84.4	105.1	84.9	108.9
Income (Loss) from Continuing Operations, Per Basic Share	$ 0.14	$ 0.05	$ 0.23	$ 0.02
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	(0.10)	0.07	(0.19)	0.13
Basic net income attributable to Trinity Industries, Inc.	0.04	0.12	0.04	0.15
Income (Loss) from Continuing Operations, Per Diluted Share	0.14	0.05	0.23	0.02
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	(0.10)	0.07	(0.19)	0.13
Diluted net income attributable to Trinity Industries, Inc.	$ 0.04	$ 0.12	$ 0.04	$ 0.15
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	0.1	0.1
Stock options
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	0.0