Consolidated Statements of Stockholders' Equity (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, 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		81,700,000				(1,500,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	253.7			255.2			255.2	(1.5)
Other comprehensive income (loss)	(14.5)				(16.1)		(16.1)	1.6
Cash dividends on common stock	(33.2)			(33.2)			(33.2)
Restricted shares, net	24.7		26.4			(1.7)	24.7
Restricted shares, net, Shares						400,000
Shares repurchased	(45.2)					(45.2)	(45.2)
Shares repurchased, Shares						(1,800,000)
Stock options exercised	4.1		(0.7)			4.8	4.1
Stock options exercised, Shares						300,000
Excess tax benefits from stock-based compensation	0.2		0.2				0.2
Stock-based compensation expense	0.2		0.2				0.2
Contributions from noncontrolling interest	0
Other	(0.7)					(0.7)	(0.7)
Other, Shares						0
Ending balance at Dec. 31, 2012	2,137.6	81.7	652.6	1,536.7	(150.1)	(67.9)	2,053.0	84.6
Ending balance, Shares at Dec. 31, 2012		81,700,000				(2,600,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	392.4			375.5			375.5	16.9
Other comprehensive income (loss)	74.7				70.5		70.5	4.2
Cash dividends on common stock	(42.2)			(42.2)			(42.2)
Restricted shares, net	37.1		23.3			13.8	37.1
Restricted shares, net, Shares						700,000
Shares repurchased	(108.2)					(108.2)	(108.2)
Shares repurchased, Shares						(2,500,000)
Stock options exercised	2.3		(2.0)			4.3	2.3
Stock options exercised, Shares						100,000
Excess tax benefits from stock-based compensation	8.7		8.7				8.7
Repurchase of interests in partially-owned leasing subsidiary	(84.2)		11.8		(11.8)			(84.2)
Sale of interests in partially-owned leasing subsidiaries	291.3		(7.3)		13.2		5.9	285.4
Contributions from noncontrolling interest	50.0							50.0
Distributions to noncontrolling interest	(9.9)							(9.9)
Other	(0.5)		(0.5)				(0.5)
Ending balance at Dec. 31, 2013	2,749.1	81.7	686.6	1,870.0	(78.2)	(158.0)	2,402.1	347.0
Ending balance, Shares at Dec. 31, 2013		81,700,000				(4,300,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	709.3			678.2			678.2	31.1
Other comprehensive income (loss)	(31.0)				(34.0)		(34.0)	3.0
Cash dividends on common stock	(58.3)			(58.3)			(58.3)
Restricted shares, net	14.9	0.1	29.8			(15.0)	14.9
Restricted shares, net, Shares		100,000				600,000
Shares repurchased	(31.5)					(31.5)	(31.5)
Shares repurchased, Shares						(600,000)
Stock options exercised	0.6	0.1	(0.1)			0.6	0.6
Stock options exercised, Shares		100,000				100,000
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	(28.2)							(28.2)
Retirement of treasury stock	0	(4.2)	(198.9)			203.1	0
Retirement of treasury stock, Shares		(4,200,000)				4,200,000
Stock split	0	78.0	(78.0)				0
Stock split, Shares		78,000,000
Other	(1.3)	0	(0.4)		0.3	(0.2)	(0.3)	(1.0)
Other, Shares		0				(100,000)
Ending balance at Dec. 31, 2014	$ 3,397.4	$ 155.7	$ 463.2	$ 2,489.9	$ (111.9)	$ (1.0)	$ 2,995.9	$ 401.5
Ending balance, Shares at Dec. 31, 2014		155,700,000				(100,000)