Consolidated Statement of Stockholders' Equity (unaudited) - USD ($) shares in Millions, $ in Millions		Total	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated other comprehensive income (loss)	Treasury Stock	Trinity Stockholders’ Equity	Noncontrolling Interest
$0.01 Par Value		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Issued			(111.2)				(0.1)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2020		$ 2,016.0	$ 1.1	$ 0.0	$ 1,769.4	$ (30.9)	$ (0.8)	$ 1,738.8	$ 277.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		1.3			3.3			3.3	(2.0)
Other comprehensive income		5.4				5.1		5.1	0.3
Cash dividends declared on common stock (1)	[1]	(23.3)			(23.3)			(23.3)
Stock-based compensation expense		5.1		5.1				5.1
Settlement of share-based awards, net		0.2		1.0			$ (0.8)	0.2
Shares repurchased							(1.3)
Shares repurchased		(36.8)					$ (36.8)	(36.8)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2021		$ 1,967.9	1.1	6.1	1,749.4	(25.8)	(38.4)	1,692.4	275.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.21
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2020		$ 2,016.0	1.1	0.0	1,769.4	(30.9)	(0.8)	1,738.8	277.2
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Dec. 31, 2021		$ 1,296.8	$ 0.8	0.0	1,046.6	(17.0)	$ (0.6)	1,029.8	267.0
$0.01 Par Value		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Issued			(111.2)				(1.4)
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued			(83.3)				0.0
Net income		$ 1.9			(0.7)			(0.7)	2.6
Other comprehensive income		17.3				17.1		17.1	0.2
Cash dividends declared on common stock (1)	[1]	(19.3)			(19.3)			(19.3)
Stock-based compensation expense		5.1		5.1				5.1
Settlement of share-based awards, net		0.0		0.2			$ (0.2)	0.0
Distributions to noncontrolling interest		(6.2)							(6.2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2022		$ 1,295.6	$ 0.8	$ 5.3	$ 1,026.6	$ 0.1	$ (0.8)	$ 1,032.0	$ 263.6
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.23
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued			(83.3)				0.0

[1] Dividends of $0.23 and $0.21 per common share for the three months ended March 31, 2022 and 2021, respectively.