Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 67.9	$ 89.6	$ 173.6	$ 290.5
Derivative financial instruments:
Unrealized losses arising during the period, net of tax expense (benefit) of $(0.1), $0.1, $(0.1), and $(0.1)	(0.6)	0.0	(0.8)	(0.7)
Reclassification adjustments for losses included in net income, net of tax benefit of $0.1, $0.1, $0.4, and $0.6	1.0	1.2	3.2	3.4
Currency translation adjustment	0.8	(0.4)	1.6	1.4
Defined benefit plans:
Amortization of net actuarial losses, net of tax benefit of $0.5, $0.4, $1.4, and $1.4	0.9	0.8	2.4	2.4
Other comprehensive income	2.1	1.6	6.4	6.5
Comprehensive income	70.0	91.2	180.0	297.0
Less: comprehensive income attributable to noncontrolling interest	1.5	6.2	11.6	16.5
Comprehensive income attributable to Trinity Industries, Inc.	$ 68.5	$ 85.0	$ 168.4	$ 280.5