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	563.0				540.0			540.0	23.0
Other comprehensive income	11.5					9.1		9.1	2.4
Cash dividends on common stock	(42.7)				(42.7)			(42.7)
Restricted shares, net	(0.4)			13.1			(13.5)	(0.4)
Restricted shares, net, Shares							600,000
Shares repurchased	(31.5)						(31.5)	(31.5)
Shares repurchased, Shares							(600,000)
Stock options exercised	0.6			0			0.6	0.6
Stock options exercised, Shares							0
Excess tax benefits from stock-based compensation	24.2			24.2				24.2
Contributions from noncontrolling interest	49.6								49.6
Distributions to noncontrolling interest	(19.3)								(19.3)
Retirement of treasury stock	0		(3.7)	(176.6)			180.3
Retirement of treasury stock, Shares			(3,700,000)				3,700,000
Stock split	0		78.0	(78.0)
Stock split, Shares			78,000,000
Other	(1.2)		0.1	(0.6)		0.3	(0.1)	(0.3)	(0.9)
Other, Shares			100,000				0
Ending balance at Sep. 30, 2014	$ 3,302.9	[1]	$ 156.1	$ 468.7	$ 2,367.3	$ (68.8)	$ (22.2)	$ 2,901.1	$ 401.8
Ending balance, Shares at Sep. 30, 2014			156,100,000				(600,000)

[1] (unaudited)