Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net income	$ 35.5	$ 23.6	$ 119.3	$ 58.5
Other comprehensive income (loss):
Unrealized gains (losses) arising during the period, net of tax benefit (expense) of $3.9, $(1.4), $2.2, and $(4.2)	(13.2)	5.0	(7.3)	14.4
Reclassification adjustments for gains included in net income, net of tax (expense) benefit of $(1.3), $(1.4), $(4.2), and $8.5	(3.8)	(4.8)	(13.1)	(23.6)
Amortization of net actuarial losses, net of tax benefit of $—, $—, $—, and $—	0.1	0.0	0.1	0.0
Other Comprehensive Income (Loss), Net of Tax, Total	(16.9)	0.2	(20.3)	(9.2)
Comprehensive income	18.6	23.8	99.0	49.3
Less: comprehensive income attributable to noncontrolling interest	4.2	1.9	10.1	8.1
Comprehensive income attributable to Trinity Industries, Inc.	$ 14.4	$ 21.9	$ 88.9	$ 41.2