Consolidated Statements of Stockholders' Equity - 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, 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	709.3			678.2			678.2	31.1
Other comprehensive income	(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	0.0	$ (4.2)	(198.9)			$ 203.1
Retirement of treasury stock, shares		(4,200,000)				(4,200,000)
Stock split, shares		78,000,000
Stock split	0.0	$ (78.0)	78.0
Other	(1.3)	0.0	(0.4)		0.3	$ (0.2)	(0.3)	(1.0)
Other, shares						(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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	826.0			796.5			796.5	29.5
Other comprehensive income	(0.5)				(3.5)		(3.5)	3.0
Cash dividends on common stock	(66.1)			(66.1)			(66.1)
Restricted shares, net	33.6	$ 0.0	64.4			$ (30.8)	33.6
Restricted shares, net, shares		(2,100,000)				(1,100,000)
Shares repurchased	$ (115.0)					$ (115.0)	(115.0)
Shares repurchased, shares	(3,947,320)					(3,900,000)
Stock options exercised	$ 0.4	$ 0.0	0.4			$ 0.0	0.4
Stock options exercised, shares		100,000				0
Excess tax benefits from stock-based compensation	12.1		12.1				12.1
Distributions to noncontrolling interest	(39.2)							(39.2)
Retirement of treasury stock	0.0	$ 0.0	(145.8)			$ (145.8)
Retirement of treasury stock, shares		(5,000,000)				(5,000,000)
Stock split, shares		0
Change in par value of common stock	0.0	$ (154.2)	154.2
Ending balance at Dec. 31, 2015	4,048.7	$ 1.5	548.5	3,220.3	(115.4)	$ (1.0)	3,653.9	394.8
Ending balance, shares at Dec. 31, 2015		152,900,000				100,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	364.7			343.6			343.6	21.1
Other comprehensive income	5.0				1.9		1.9	3.1
Cash dividends on common stock	(66.6)			(66.6)			(66.6)
Restricted shares, net	25.0	$ 0.1	46.2			$ (21.3)	25.0
Restricted shares, net, shares		(2,600,000)				(1,200,000)
Shares repurchased	$ (34.7)					$ (34.7)	(34.7)
Shares repurchased, shares	(2,070,600)					(2,100,000)
Stock options exercised, shares	0
Excess net tax deficiency from stock-based compensation	$ (4.5)		(4.5)				(4.5)
Distributions to noncontrolling interest	(26.4)						0.0	(26.4)
Retirement of treasury stock	0.0	$ 0.0	56.0			$ (56.0)	0.0
Retirement of treasury stock, shares		(3,300,000)				(3,300,000)
Other	(0.1)		(0.4)			$ 0.5	(0.1)
Ending balance at Dec. 31, 2016	$ 4,311.1	$ 1.6	$ 534.6	$ 3,497.3	$ (113.5)	$ (1.5)	$ 3,918.5	$ 392.6
Ending balance, shares at Dec. 31, 2016		152,200,000				100,000