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, 2021		Sep. 30, 2021		Jun. 30, 2021		Mar. 31, 2021		Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Income (loss) from continuing operations	$ 21.6		$ 25.5		$ (2.8)		$ (5.0)		$ (133.2)		$ 19.0		$ (294.6)		$ 158.3		$ 39.3	$ (250.5)	$ 122.4
Less: Net loss attributable to noncontrolling interest	(5.8)		(3.9)		7.9		2.0		(0.6)		(0.8)		80.9		(0.6)		0.2	78.9	1.5
Unvested restricted share participation – continuing operations																	0.0	0.0	(1.7)
Net income (loss) from continuing operations attributable to Trinity Industries, Inc.																	39.5	(171.6)	122.2
Income from discontinued operations, net of provision for income taxes of $3.5, $5.5, and $1.7	(13.2)		10.4		7.6		6.3		$ 6.6		$ 6.9		$ 6.8		$ 4.0		11.1	24.3	13.7
Gain on sale of discontinued operations, net of provision for income taxes of $51.9, $—, and $—	$ 131.4		$ 0.0		$ 0.0		$ 0.0										131.4	0.0	0.0
Unvested restricted share participation – discontinued operations																	0.0	0.0	(0.1)
Net income from discontinued operations attributable to Trinity Industries, Inc.																	142.5	24.3	13.6
Net income (loss) attributable to Trinity Industries, Inc., including the effect of unvested restricted share participation																	$ 182.0	$ (147.3)	$ 135.8
Basic weighted average shares outstanding																	101.5	115.9	125.6
Effect of dilutive securities																	2.3	0.0	1.7
Diluted weighted average shares outstanding																	103.8	115.9	127.3
Income (loss) from continuing operations	$ 0.16	[1]	$ 0.22	[1]	$ 0.05	[1]	$ (0.03)	[1]	$ (1.19)	[1]	$ 0.15	[1]	$ (1.82)	[1]	$ 1.32	[1]	$ 0.39	$ (1.48)	$ 0.98
Income from discontinued operations	1.23	[1]	0.11	[1]	0.07	[1]	0.06	[1]	0.06	[1]	0.06	[1]	0.06	[1]	0.04	[1]	1.40	0.21	0.11
Basic net income (loss) attributable to Trinity Industries, Inc.	1.39	[1]	0.33	[1]	0.12	[1]	0.03	[1]	(1.13)	[1]	0.21	[1]	(1.76)	[1]	1.36	[1]	1.79	(1.27)	1.09
Income (loss) from continuing operations	0.16	[1]	0.22	[1]	0.05	[1]	(0.03)	[1]	(1.19)	[1]	0.15	[1]	(1.82)	[1]	1.30	[1]	0.38	(1.48)	0.96
Income from discontinued operations	1.21	[1]	0.11	[1]	0.07	[1]	0.06	[1]	0.06	[1]	0.06	[1]	0.06	[1]	0.03	[1]	1.37	0.21	0.11
Diluted net income (loss) attributable to Trinity Industries, Inc.	$ 1.37	[1]	$ 0.33	[1]	$ 0.12	[1]	$ 0.03	[1]	$ (1.13)	[1]	$ 0.21	[1]	$ (1.76)	[1]	$ 1.33	[1]	$ 1.75	$ (1.27)	$ 1.07
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	0.0	0.2
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.