Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 23.6	$ 26.3	$ 58.5	$ 36.7
Other comprehensive income (loss):
Unrealized gains arising during the period, net of tax expense of $1.4, $3.0, $4.2, and $8.4	5.0	10.0	14.4	26.8
Reclassification adjustments for (gains) losses included in net income, net of tax (expense) benefit of $(1.4), $(0.1), $8.5, and $1.2	(4.8)	0.2	(23.6)	4.6
Amortization of net actuarial losses, net of tax benefit of $—, $—, $—, and $—	0.0	0.1	0.0	0.2
Reclassification adjustments for losses included in discontinued operations, net of tax benefit of $—, $—, $—, and $—	0.0	0.0	0.0	1.3
Other Comprehensive Income (Loss), Net of Tax, Total	0.2	10.3	(9.2)	32.9
Comprehensive income	23.8	36.6	49.3	69.6
Less: comprehensive income attributable to noncontrolling interest	1.9	0.8	8.1	7.4
Comprehensive income attributable to Trinity Industries, Inc.	$ 21.9	$ 35.8	$ 41.2	$ 62.2