Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 35.9	$ 25.9	$ 42.0	$ (99.6)
Derivative financial instruments:
Unrealized gains (losses) arising during the period, net of tax benefit (expense) of $0.2, $(0.6), $(1.5), and $7.6	(0.8)	2.0	5.0	(25.3)
Reclassification adjustments for losses included in net income, net of tax benefit of $0.3, $1.3, $0.6, and $3.0	1.8	4.7	2.9	10.6
Defined benefit plans:
Amortization of prior service cost, net of tax benefit of $—, $0.1, $—, and $0.3	0.0	0.2	0.0	0.6
Amortization of net actuarial losses, net of tax benefit of $—, $0.3, $0.1, and $0.9	0.0	1.2	0.1	3.6
Other Comprehensive Income (Loss), Net of Tax, Total	1.0	8.1	8.0	(10.5)
Comprehensive income (loss)	36.9	34.0	50.0	(110.1)
Less: comprehensive income (loss) attributable to noncontrolling interest	4.2	1.1	(5.0)	(78.6)
Comprehensive income (loss) attributable to Trinity Industries, Inc.	$ 32.7	$ 32.9	$ 55.0	$ (31.5)