Consolidated Statement of Stockholders' Equity (unaudited) - USD ($) shares in Millions, $ in Millions		Total	Accelerated Share Repurchase Program	Common Stock	Capital in Excess of Par Value	Capital in Excess of Par Value Accelerated Share Repurchase Program	Retained Earnings	Accumulated other comprehensive income (loss)	Treasury Stock	Treasury Stock Accelerated Share Repurchase Program	Trinity Stockholders’ Equity	Trinity Stockholders’ Equity Accelerated Share Repurchase Program	Noncontrolling Interest
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)
Treasury Stock, Value, Acquired, Cost Method		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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		6.1
Other comprehensive income		7.0
Stock-based compensation expense		9.2
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2021		$ 1,657.9		$ 1.0	0.0		1,414.1	(24.6)	$ (0.6)		1,389.9		268.0
$0.01 Par Value		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Issued				(111.2)					(1.4)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning 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]
Net income		4.8					12.7				12.7		(7.9)
Other comprehensive income		1.6						1.2			1.2		0.4
Cash dividends declared on common stock (1)	[1]	(21.0)					(21.0)				(21.0)
Stock-based compensation expense		4.1			4.1						4.1
Restricted shares, net, (in shares)									(0.3)
Settlement of share-based awards, net		(8.7)		$ 1.1	0.4				$ (9.1)		(8.7)
Shares repurchased									(10.5)
Treasury Stock, Value, Acquired, Cost Method		290.8							$ 290.8		290.8
Treasury Stock, Shares, Retired				(12.2)					(12.2)
Retirement of treasury stock		0.0		$ 0.1	(10.6)		(327.0)		$ (337.7)		0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2021		$ 1,657.9		$ 1.0	0.0		1,414.1	(24.6)	$ (0.6)		1,389.9		268.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Dividends, Per Share, Declared		$ 0.21
$0.01 Par Value		$ 0.01
Common Stock, Shares, Issued				(100.1)					0.0
Common Stock, Shares, Issued				(83.3)					0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2021		$ 1,296.8		$ 0.8	0.0		1,046.6	(17.0)	$ (0.6)		1,029.8		267.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
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)
Distributions to noncontrolling interest		(6.2)											(6.2)
Stock-based compensation expense		5.1			5.1						5.1
Settlement of share-based awards, net		0.0			0.2				(0.2)		0.0
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
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning Balance at Dec. 31, 2021		$ 1,296.8		0.8	0.0		1,046.6	(17.0)	(0.6)		1,029.8		267.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		10.4
Other comprehensive income		22.6											(0.8)
Stock-based compensation expense		10.8
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2022		$ 1,256.2		$ 0.8	0.0		991.1	6.4	$ (0.7)		997.6		258.6
$0.01 Par Value		$ 0.01
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Issued				(83.3)					0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Beginning 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]
Net income		8.5					3.7				3.7		4.8
Other comprehensive income		5.3						6.3			6.3		(1.0)
Cash dividends declared on common stock (1)		(19.1)					(19.1)				(19.1)
Distributions to noncontrolling interest		(8.8)											(8.8)
Stock-based compensation expense		5.7			5.7						5.7
Restricted shares, net, (in shares)				(0.8)					(0.2)
Settlement of share-based awards, net		(5.7)			0.4				$ (6.1)		(5.7)
Shares repurchased									(1.0)	(0.8)
Treasury Stock, Value, Acquired, Cost Method		25.3	$ 0.0			$ 25.0			$ 25.3	$ 25.0	25.3	$ 0.0
Treasury Stock, Shares, Retired				(2.0)					(2.0)
Retirement of treasury stock		0.0			(36.4)		(20.1)		$ (56.5)		0.0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Ending Balance at Jun. 30, 2022		$ 1,256.2		$ 0.8	$ 0.0		$ 991.1	$ 6.4	$ (0.7)		$ 997.6		$ 258.6
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				(82.1)					0.0

[1] $0.21 per common share for all periods presented in 2021.