Consolidated Statement of Stockholders' Equity (unaudited) (USD $) In Millions, except Share data, unless otherwise specified	Total		Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock	Trinity Stockholders' Equity	Noncontrolling Interest
Beginning balance at Dec. 31, 2013	$ 2,749.1		$ 81.7	$ 686.6	$ 1,870.0	$ (78.2)	$ (158.0)	$ 2,402.1	$ 347.0
Beginning balance, Shares at Dec. 31, 2013			81,700,000				(4,300,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	233.0				226.4			226.4	6.6
Other comprehensive income	3.3					2.6		2.6	0.7
Cash dividends on common stock	(11.6)				(11.6)			(11.6)
Restricted shares, net	10.8			9.5			1.3	10.8
Restricted shares, net, Shares							100,000
Shares repurchased	(10.0)						(10.0)	(10.0)
Shares repurchased, Shares							(100,000)
Stock options exercised	0.3			(0.1)			0.4	0.3
Stock options exercised, Shares							0
Excess tax benefits from stock-based compensation	0.4			0.4				0.4
Distributions to noncontrolling interest	(5.4)								(5.4)
Other	0			0			(0.1)	(0.1)	0.1
Ending balance at Mar. 31, 2014	$ 2,969.9	[1]	$ 81.7	$ 696.4	$ 2,084.8	$ (75.6)	$ (166.4)	$ 2,620.9	$ 349.0
Ending balance, Shares at Mar. 31, 2014			81,700,000				(4,300,000)

[1] (unaudited)