Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net income	$ 126.6	$ 72.9	$ 181.8
Unrealized gains arising during the period, net of tax expense of $3.3, $9.2, and $2.8	10.6	29.3	9.2
Reclassification adjustments for (gains) losses included in net income, net of tax benefit of $7.4, $0.8, and $1.2	(26.1)	3.5	5.4
Unrealized gains (losses) arising during the period, net of tax expense (benefit) of $(0.1), $0.5, and $0.1	(0.3)	2.1	0.3
Amortization of net actuarial losses, net of tax benefit of $—, $0.1, and $0.1	0.1	0.2	0.2
Reclassification adjustments for losses included in discontinued operations, net of tax benefit of $—, $—, and $—	0.0	(1.3)	0.0
Other comprehensive income (loss):	(15.7)	36.4	15.1
Comprehensive income	110.9	109.3	196.9
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	13.6	12.5	1.0
Comprehensive income attributable to Trinity Industries, Inc.	$ 97.3	$ 96.8	$ 195.9