Earnings Per Common Share - Computation of basic and diluted net income attributable to Trinity Industries, Inc. - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Total weighted average restricted shares and antidilutive stock options									6.4	6.6	6.8
Earnings Per Share Reconciliation [Abstract]
Net income	$ 540.0	$ 67.9	$ 54.0	$ 51.7	$ 74.2	$ 89.6	$ 98.8	$ 102.1	$ 713.6	$ 364.7	$ 826.0
Net income attributable to noncontrolling interest									11.1	21.1	29.5
Net income attributable to Trinity Industries, Inc.	$ 538.5	$ 66.9	$ 51.1	$ 46.0	$ 67.6	$ 84.2	$ 94.6	$ 97.2	702.5	343.6	796.5
Unvested restricted share participation									(15.4)	(9.4)	(24.1)
Net income attributable to Trinity Industries, Inc. – basic									$ 687.1	$ 334.2	$ 772.4
Net income attributable to Trinity Industries, Inc. - basic (shares)									148.6	148.4	150.2
Net income attributable to Trinity Industries, Inc. - basic (EPS)	$ 3.56	$ 0.44	$ 0.34	$ 0.30	$ 0.44	$ 0.55	$ 0.62	$ 0.64	$ 4.62	$ 2.25	$ 5.14
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Stock options									$ 0.0	$ 0.0	$ 0.0
Stock options (shares)									0.5	0.0	0.0
Convertible subordinated notes									$ 0.3	$ 0.0	$ 0.3
Convertible subordinated notes (shares)									2.9	0.2	2.0
Net income attributable to Trinity Industries, Inc. – diluted									$ 687.4	$ 334.2	$ 772.7
Net income attributable to Trinity Industries, Inc - diluted (shares)									152.0	148.6	152.2
Net income attributable to Trinity Industries, Inc. - diluted (EPS)	$ 3.42	$ 0.43	$ 0.33	$ 0.30	$ 0.44	$ 0.55	$ 0.62	$ 0.64	$ 4.52	$ 2.25	$ 5.08