Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 47.7	$ 28.3	$ 114.6	$ 135.4
Derivative financial instruments:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	(4.6)	0.2	(18.1)	0.1
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	1.0	0.4	2.9	1.7
Currency translation adjustment	0.0	0.5	0.0	(1.0)
Defined benefit plans:
Amortization of net actuarial losses, net of tax benefit	0.9	1.0	2.5	2.7
Other comprehensive income	(2.7)	2.1	(12.7)	3.5
Comprehensive income	45.0	30.4	101.9	138.9
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	(0.9)	0.9	(0.4)	4.5
Comprehensive income attributable to Trinity Industries, Inc.	$ 45.9	$ 29.5	$ 102.3	$ 134.4