Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 4.8	$ (287.8)	$ 6.1	$ (125.5)
Derivative financial instruments:
Unrealized gains (losses) arising during the period, net of tax benefit (expense) of $0.3, $0.5, $(1.7), and $8.2	(0.4)	(1.7)	5.8	(27.3)
Reclassification adjustments for losses included in net income, net of tax benefit (expense) of $(0.6), $1.2, $0.3, and $1.7	2.0	4.9	1.1	5.9
Defined benefit plans:
Amortization of prior service cost, net of tax benefit of $—, $0.1, $—, and $0.2	0.0	0.2	0.0	0.4
Amortization of net actuarial losses, net of tax benefit of $0.1, $0.3, $0.1, and $0.6	0.0	1.2	0.1	2.4
Other Comprehensive Income (Loss), Net of Tax, Total	1.6	4.6	7.0	(18.6)
Comprehensive income (loss)	6.4	(283.2)	13.1	(144.1)
Less: comprehensive loss attributable to noncontrolling interest	(7.5)	(80.6)	(9.2)	(79.7)
Comprehensive income (loss) attributable to Trinity Industries, Inc.	$ 13.9	$ (202.6)	$ 22.3	$ (64.4)