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			(81.1)				0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2022		$ 1,269.6	$ 0.8	$ 0.0	$ 992.6	$ 19.7	$ (0.7)	$ 1,012.4	$ 257.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		13.7			4.4			4.4	9.3
Other comprehensive income		(14.4)				(7.0)		(7.0)	(7.4)
Cash dividends declared on common stock (1)	[1]	(21.4)			(21.4)			(21.4)
Distributions to noncontrolling interest		(2.9)							(2.9)
Stock-based compensation expense		6.2		6.2				6.2
Settlement of share-based awards, net		(0.4)		0.4			(0.8)	(0.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2023		$ 1,250.4	$ 0.8	6.6	975.6	12.7	$ (1.5)	994.2	256.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.26
$0.01 Par Value		0.01
Common Stock, Shares, Issued			(81.1)				0.0
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued			(81.8)				0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2023		$ 1,275.5	$ 0.8	15.4	1,010.5	11.0	$ (0.6)	1,037.1	238.4
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		27.4			23.7			23.7	3.7
Other comprehensive income		7.5				7.4		7.4	0.1
Cash dividends declared on common stock (1)	[1]	(23.3)			(23.3)			(23.3)
Distributions to noncontrolling interest		(3.0)							(3.0)
Stock-based compensation expense		4.7		4.7				4.7
Settlement of share-based awards, net		(0.3)		0.1			(0.4)	(0.3)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2024		$ 1,288.5	$ 0.8	$ 20.2	$ 1,010.9	$ 18.4	$ (1.0)	$ 1,049.3	$ 239.2
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.28
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued			(81.8)				0.0

[1] Dividends of $0.28 and $0.26 per common share for the three months ended March 31, 2024 and 2023, respectively