Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 41.6	$ 51.7
Derivative financial instruments:
Unrealized gains arising during the period, net of tax expense of $0.2 and $-	0.8	0.0
Reclassification adjustments for losses included in net income, net of tax expense (benefit) of $0.3 and $(0.3)	1.0	1.0
Currency translation adjustment	(0.7)	0.3
Defined benefit plans:
Amortization of net actuarial losses, net of tax benefit of $0.4 and $0.4	0.8	0.8
Other comprehensive income	1.9	2.1
Comprehensive income	43.5	53.8
Less: comprehensive income attributable to noncontrolling interest	1.8	6.5
Comprehensive income attributable to Trinity Industries, Inc.	$ 41.7	$ 47.3