Summary of Significant Accounting Policies Property, Plant, and Equipment (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Change in Accounting Estimate [Line Items]
Depreciation and amortization			$ 199.5	$ 210.5
Basic net income (loss) attributable to Trinity Industries, Inc.	$ 0.21	$ 0.39	$ (0.17)	$ 0.89
Diluted net income (loss) attributable to Trinity Industries, Inc.	$ 0.21	$ 0.39	$ (0.17)	$ 0.88
Service Life [Member]
Change in Accounting Estimate [Line Items]
Depreciation and amortization	$ 7.7		$ 23.1
Depreciation, Amortization and Accretion, Net	$ 5.9		$ 17.7
Basic net income (loss) attributable to Trinity Industries, Inc.	$ 0.05		$ 0.15
Diluted net income (loss) attributable to Trinity Industries, Inc.	$ 0.05		$ 0.15