Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 28.3	$ 67.9	$ 135.4	$ 173.6
Derivative financial instruments:
Unrealized gains (losses) arising during the period, net of tax expense (benefit) of $-, $(0.1), $-, and $(0.1)	0.2	(0.6)	0.1	(0.8)
Reclassification adjustments for losses included in net income, net of tax benefit of $0.2, $0.1, $0.1, and $0.4	0.4	1.0	1.7	3.2
Currency translation adjustment	0.5	0.8	(1.0)	1.6
Defined benefit plans:
Amortization of net actuarial losses, net of tax benefit of $0.2, $0.5, $0.6, and $0.9	1.0	0.9	2.7	2.4
Other comprehensive income	2.1	2.1	3.5	6.4
Comprehensive income	30.4	70.0	138.9	180.0
Less: comprehensive income attributable to noncontrolling interest	0.9	1.5	4.5	11.6
Comprehensive income attributable to Trinity Industries, Inc.	$ 29.5	$ 68.5	$ 134.4	$ 168.4