Earnings Per Common Share - EPS calculation (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic and Diluted	5.5	5.6	5.5	5.5
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ (287.8)	$ 37.6	$ (125.3)	$ 68.8
Net Income (Loss) Attributable to Noncontrolling Interest	80.9	(0.4)	80.3	0.1
Participating Securities, Distributed and Undistributed Earnings (Loss), Basic	0.0	(0.3)	0.0	(0.9)
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Basic	(206.9)	36.9	(45.0)	68.0
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	0.0	(0.8)	(0.2)	(1.9)
Undistributed Discontinued Operation Earnings (Loss), Allocation to Participating Securities, Basic	0.0	0.0	0.0	0.0
Net Income (Loss) from Discontinued Operations Available to Common Shareholders, Basic	0.0	(0.8)	(0.2)	(1.9)
Net Income (Loss) Available to Common Stockholders, Basic	$ (206.9)	$ 36.1	$ (45.2)	$ 66.1
Income (Loss) from Continuing Operations, Per Basic Share	$ (1.76)	$ 0.29	$ (0.38)	$ 0.53
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	0	(0.01)	0	(0.02)
Net income attributable to Trinity Industries, Inc. - basic, EPS (in dollars per share)	(1.76)	0.28	(0.38)	0.51
Income (Loss) from Continuing Operations, Per Diluted Share	(1.76)	0.29	(0.38)	0.52
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Diluted Share	0	(0.01)	0	(0.01)
Net income attributable to Trinity Industries, Inc. - diluted, EPS (in dollars per share)	$ (1.76)	$ 0.28	$ (0.38)	$ 0.51
Computation of basic and diluted net income attributable to Trinity Industries, Inc
Weighted Average Number of Shares Outstanding, Basic	117.3	127.6	117.6	129.0
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	0.0	1.6	0.0	1.7
Weighted Average Number of Shares Outstanding, Diluted, Total	117.3	129.2	117.6	130.7
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	0.6	0.0	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