Consolidated Statement of Stockholders' Equity (unaudited) - USD ($) shares in Millions, $ in Millions		Total	Trinity Stockholders’ Equity	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated other comprehensive income (loss)	Treasury Stock	Noncontrolling Interest
$0.01 Par Value		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Issued				(81.8)
Treasury Stock, Common, Shares								0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2024		$ 1,307.2	$ 1,058.9	$ 0.8	$ 8.8	$ 1,054.1	$ (4.2)	$ (0.6)	$ 248.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		27.1	22.1			22.1			5.0
Other comprehensive income		0.1	0.0				0.0		0.1
Cash dividends declared on common stock (1)	[1]	(24.6)	(24.6)			(24.6)
Distributions to noncontrolling interest		(6.9)							(6.9)
Stock-based compensation expense		5.3	5.3		5.3
Settlement of share-based awards, net		(0.3)	(0.3)					$ (0.3)
Treasury Stock, Shares, Acquired								(0.3)
Treasury Stock, Value, Acquired, Cost Method		(8.2)	(8.2)					$ (8.2)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2025		$ 1,299.7	1,053.2	$ 0.8	14.1	1,051.6	(4.2)	$ (9.1)	246.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.30
$0.01 Par Value		0.01
Common Stock, Shares, Issued				(81.8)
Treasury Stock, Common, Shares								0.3
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued				(79.8)
Treasury Stock, Common, Shares								0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2025		$ 1,145.3	1,077.2	$ 0.8	0.0	1,081.5	(4.2)	$ (0.9)	68.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		24.8	24.2			24.2			0.6
Other comprehensive income		5.2	5.2				5.2		0.0
Cash dividends declared on common stock (1)	[1]	(25.1)	(25.1)			(25.1)
Distributions to noncontrolling interest		(1.8)							(1.8)
Stock-based compensation expense		4.9	4.9		4.9
Settlement of share-based awards, net		(0.2)	(0.2)					$ (0.2)
Treasury Stock, Shares, Acquired								(0.2)
Treasury Stock, Value, Acquired, Cost Method		(7.4)	(7.4)					$ (7.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Mar. 31, 2026		$ 1,145.7	$ 1,078.8	$ 0.8	$ 4.9	$ 1,080.6	$ 1.0	$ (8.5)	$ 66.9
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.31
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued				(79.8)
Treasury Stock, Common, Shares								0.2

[1] Dividends of $0.31 and $0.30 per common share for the three months ended March 31, 2026 and 2025, respectively.