Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 65.5	$ 54.0	$ 107.1	$ 105.7
Derivative financial instruments:
Unrealized losses arising during the period, net of tax expense (benefit) of $(0.2), $-, $-, and $-	(0.9)	(0.2)	(0.1)	(0.2)
Reclassification adjustments for losses included in net income, net of tax expense (benefit) of $(0.2), $-, $0.1, and $(0.3)	0.3	1.2	1.3	2.2
Currency translation adjustment	(0.8)	0.5	(1.5)	0.8
Defined benefit plans:
Amortization of net actuarial losses, net of tax benefit of $0.2, $0.5, $0.6, and $0.9	0.9	0.7	1.7	1.5
Other comprehensive income	(0.5)	2.2	1.4	4.3
Comprehensive income	65.0	56.2	108.5	110.0
Less: comprehensive income attributable to noncontrolling interest	1.8	3.6	3.6	10.1
Comprehensive income attributable to Trinity Industries, Inc.	$ 63.2	$ 52.6	$ 104.9	$ 99.9