Consolidated Statement of Stockholders' Equity (Unaudited) (USD $) In Millions	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, 2011	$ 1,948.3	$ 81.7	$ 626.5	$ 1,314.7	$ (134.0)	$ (25.1)	$ 1,863.8	$ 84.5
Beginning Balance, Shares at Dec. 31, 2011		81.7				(1.5)
Net income	52.3			52.9			52.9	(0.6)
Other comprehensive income	3.5				3.0		3.0	0.5
Cash dividends on common stock	(7.2)			(7.2)			(7.2)
Restricted shares issued, net	6.2		6.2			0	6.2
Restricted shares issued, net, Shares						0
Stock options exercised	0.7		0.5			0.2	0.7
Stock options exercised, Shares						0.1
Stock-based compensation expense	0.5		0.5				0.5
Ending Balance at Mar. 31, 2012	$ 2,004.3	$ 81.7	$ 633.7	$ 1,360.4	$ (131.0)	$ (24.9)	$ 1,919.9	$ 84.4
Ending Balance, Shares at Mar. 31, 2012		81.7				(1.4)