Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Statement of Comprehensive Income [Abstract]
Net income	$ 21.2	$ 8.5	$ 34.9	$ 10.4
Other comprehensive income (loss):
Unrealized gains arising during the period, net of tax expense of $2.7,$1.0, $2.8, and $5.4	8.9	2.1	9.4	16.8
Reclassification adjustments for (gains) losses included in net income, net of tax (expense) benefit of $(1.1), $0.4, $9.9, and $1.3	(3.9)	1.9	(18.8)	4.4
Amortization of net actuarial losses, net of tax benefit of $—, $—, $—, and $—	0.0	0.0	0.0	0.1
Reclassification adjustments for losses included in discontinued operations, net of tax benefit of $—, $—, $—, and $—	0.0	1.3	0.0	1.3
Other Comprehensive Income (Loss), Net of Tax, Total	5.0	5.3	(9.4)	22.6
Comprehensive income	26.2	13.8	25.5	33.0
Less: comprehensive income attributable to noncontrolling interest	4.3	3.8	6.2	6.6
Comprehensive income attributable to Trinity Industries, Inc.	$ 21.9	$ 10.0	$ 19.3	$ 26.4