Summary of Significant Accounting Policies - ASU 2014-09 Adoption (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018		Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		$ 831.3		$ 877.3
Cost of revenues		630.1		660.2
Operating Profit (Loss)		98.6		115.9
Income before income taxes		56.4		72.5
Provision for income taxes		14.8		20.8
Net income		41.6		51.7
Net income attributable to Trinity Industries, Inc.		40.2		46.0
Receivables, net of allowance		342.5	[1]		$ 369.7
Raw materials and supplies		272.6	[1]		296.7
Work in process		164.4	[1]		179.0
Finished goods		162.4	[1]		164.9
Accrued liabilities		396.4	[1]		440.0
Deferred income taxes		757.0	[1]		743.2
Retained earnings		4,158.9	[1]		$ 4,123.4
Provision for deferred income taxes		14.4		55.3
(Increase) decrease in receivables		49.4		24.1
(Increase) decrease in inventories		13.1		33.7
Increase (decrease) in accrued liabilities		(42.6)		(26.6)
Net cash provided (required) by operating activities		173.7		220.1
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Profit (Loss)		4.0
Income before income taxes		4.0
Provision for income taxes		0.9
Net income		3.1
Net income attributable to Trinity Industries, Inc.		3.1
Receivables, net of allowance	[1]	(10.1)
Raw materials and supplies	[1]	0.0
Work in process	[1]	12.9
Finished goods	[1]	0.7
Accrued liabilities	[1]	(5.6)
Deferred income taxes	[1]	2.0
Retained earnings	[1]	7.1
Provision for deferred income taxes		0.8
(Increase) decrease in receivables		2.3
(Increase) decrease in inventories		14.0
Increase (decrease) in accrued liabilities		(20.2)
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)		102.6
Income before income taxes		60.4
Provision for income taxes		15.7
Net income		44.7
Net income attributable to Trinity Industries, Inc.		43.3
Receivables, net of allowance	[1]	332.4
Raw materials and supplies	[1]	272.6
Work in process	[1]	177.3
Finished goods	[1]	163.1
Accrued liabilities	[1]	390.8
Deferred income taxes	[1]	759.0
Retained earnings	[1]	4,166.0
Provision for deferred income taxes		15.2
(Increase) decrease in receivables		51.7
(Increase) decrease in inventories		27.1
Increase (decrease) in accrued liabilities		(62.8)
Net cash provided (required) by operating activities		173.7
Manufacturing
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		657.0		698.7
Cost of revenues		536.7		$ 576.6
Manufacturing | Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		18.0
Cost of revenues		14.0
Manufacturing | Balance without adjustment for ASU 2014-09 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total revenues		675.0
Cost of revenues		$ 550.7

[1] (unaudited)