Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 25.9	$ 47.7	$ (99.6)	$ 114.6
Derivative financial instruments:
Unrealized gains (losses) arising during the period, net of tax benefit (expense) of $(0.6), $1.4, $7.6, and $5.5	2.0	(4.6)	(25.3)	(18.1)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	(0.6)	1.4	7.6	5.5
Reclassification adjustments for losses included in net income, net of tax benefit of $1.3, $0.3, $3.0, and $0.7	4.7	1.0	10.6	2.9
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	1.3	0.3	3.0	0.7
Defined benefit plans:
Amortization of prior service cost, net of tax benefit of $0.1, $—, $0.3, and $—	0.2	0.0	0.6	0.0
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax	0.1	0.0	0.3	0.0
Amortization of net actuarial losses, net of tax benefit of $0.3, $0.3, $0.9, and $0.9	1.2	0.9	3.6	2.5
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax	0.3	0.3	0.9	0.9
Other Comprehensive Income (Loss), Net of Tax, Total	8.1	(2.7)	(10.5)	(12.7)
Comprehensive income (loss)	34.0	45.0	(110.1)	101.9
Less: comprehensive income (loss) attributable to noncontrolling interest	1.1	(0.9)	(78.6)	(0.4)
Comprehensive income (loss) attributable to Trinity Industries, Inc.	$ 32.9	$ 45.9	$ (31.5)	$ 102.3