Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Net income (loss)	$ (226.2)	$ 136.1	$ 163.1
Unrealized losses arising during the period, net of tax benefit of $5.9, $3.8, and $3.0	(19.4)	(12.8)	(9.6)
Reclassification adjustments for losses included in net income, net of tax benefit of $3.5, $0.8, and $0.4	12.9	4.5	2.3
Settlement of pension plan, net of tax benefit of $34.9, $—, and $—	116.6	0.0	0.0
Unrealized gains (losses) arising during the period, net of tax benefit of $2.7, $9.0, and $2.9	7.7	(30.2)	(9.5)
Amortization of prior service cost, net of tax benefit of $0.3, $—, and $—	0.9	0.0	0.0
Amortization of net actuarial losses, net of tax benefit of $1.3, $1.1, and $1.1	4.7	3.5	3.6
Other comprehensive income (loss):	123.4	(35.0)	(13.2)
Comprehensive income (loss)	(102.8)	101.1	149.9
Less: comprehensive income (loss) attributable to noncontrolling interest	(77.7)	(0.2)	5.2
Comprehensive income (loss) attributable to Trinity Industries, Inc.	$ (25.1)	$ 101.3	$ 144.7