Summary of Significant Accounting Policies - ASU 2014-09 Adoption (Details) - USD ($) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018		Jun. 30, 2017	Jun. 30, 2018		Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		$ 942.3		$ 905.5	$ 1,773.6		$ 1,782.8
Cost of revenues		718.1		682.3	1,348.2		1,342.5
Operating Profit (Loss)		125.5		134.6	224.1		250.5
Income before income taxes		86.1		91.3	142.5		163.8
Provision for income taxes		20.6		37.3	35.4		58.1
Net income		65.5		54.0	107.1		105.7
Net income attributable to Trinity Industries, Inc.		64.1		51.1	104.3		97.1
Receivables, net of allowance		356.1	[1]		356.1	[1]		$ 369.7
Raw materials and supplies		300.4	[1]		300.4	[1]		296.7
Work in process		149.2	[1]		149.2	[1]		179.0
Finished goods		136.8	[1]		136.8	[1]		164.9
Accrued liabilities		435.0	[1]		435.0	[1]		440.0
Deferred income taxes		734.0	[1]		734.0	[1]		743.2
Retained earnings		4,203.4	[1]		4,203.4	[1]		$ 4,123.4
Provision for deferred income taxes					36.2		116.4
(Increase) decrease in receivables					31.8		(52.8)
(Increase) decrease in inventories					26.1		39.6
Increase (decrease) in accrued liabilities					(27.8)		(4.9)
Net cash provided (required) by operating activities					348.3		336.1
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Profit (Loss)		(0.4)			3.6
Income before income taxes		(0.4)			3.6
Provision for income taxes		(0.1)			0.8
Net income		(0.3)			2.8
Net income attributable to Trinity Industries, Inc.		(0.3)			2.8
Receivables, net of allowance	[1]	(12.0)			(12.0)
Raw materials and supplies	[1]	0.0			0.0
Work in process	[1]	15.7			15.7
Finished goods	[1]	0.8			0.8
Accrued liabilities	[1]	(4.3)			(4.3)
Deferred income taxes	[1]	2.0			2.0
Retained earnings	[1]	6.8			6.8
Provision for deferred income taxes					0.8
(Increase) decrease in receivables					4.1
(Increase) decrease in inventories					11.1
Increase (decrease) in accrued liabilities					(18.8)
Net cash provided (required) by operating activities					0.0
Balance without adjustment for ASU 2014-09 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Profit (Loss)		125.1			227.7
Income before income taxes		85.7			146.1
Provision for income taxes		20.5			36.2
Net income		65.2			109.9
Net income attributable to Trinity Industries, Inc.		63.8			107.1
Receivables, net of allowance	[1]	344.1			344.1
Raw materials and supplies	[1]	300.4			300.4
Work in process	[1]	164.9			164.9
Finished goods	[1]	137.6			137.6
Accrued liabilities	[1]	430.7			430.7
Deferred income taxes	[1]	736.0			736.0
Retained earnings	[1]	4,210.2			4,210.2
Provision for deferred income taxes					37.0
(Increase) decrease in receivables					35.9
(Increase) decrease in inventories					37.2
Increase (decrease) in accrued liabilities					(46.6)
Net cash provided (required) by operating activities					348.3
Manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		729.1		713.6	1,386.1		1,412.3
Cost of revenues		599.6		$ 590.1	1,136.3		$ 1,166.7
Manufacturing | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		(3.3)			14.7
Cost of revenues		(2.9)			11.1
Manufacturing | Balance without adjustment for ASU 2014-09 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		725.8			1,400.8
Cost of revenues		$ 596.7			$ 1,147.4

[1] (unaudited)