Note 1. Summary of Significant Accounting Policies Change in Depreciable Lives (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Accounting Estimate [Line Items]
Depreciation and amortization	$ 266.0	$ 283.6	$ 251.9
Basic net income (loss) attributable to Trinity Industries, Inc.	$ (1.27)	$ 1.09	$ 1.09
Diluted net income (loss) attributable to Trinity Industries, Inc.	$ (1.27)	$ 1.07	$ 1.07
Service Life [Member]
Change in Accounting Estimate [Line Items]
Depreciation and amortization	$ 30.8
Depreciation, Amortization and Accretion, Net	$ 23.7
Basic net income (loss) attributable to Trinity Industries, Inc.	$ 0.20
Diluted net income (loss) attributable to Trinity Industries, Inc.	$ 0.20