Note 8. Intangible Assets, Goodwill and Other (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Oct. 01, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Goodwill [Line Items]
Goodwill		$ 221.5	$ 195.9
Goodwill, Acquired During Period		26.8
Goodwill, Written off Related to Sale of Business Unit		(1.2)
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Indefinite-Lived (Excluding Goodwill)	$ 0.0		0.0
Finite-Lived Intangible Assets, Gross		126.1	92.9
Finite-Lived Intangible Assets, Accumulated Amortization		(30.6)	(18.3)
Finite-Lived Intangible Assets, Net		95.5	74.6
Intangible Assets, Gross (Excluding Goodwill)		137.3	97.3
Intangible Assets, Net (Excluding Goodwill)		106.7	79.0
Amortization of Intangible Assets		13.0	5.5	$ 4.6
Finite-Lived Intangible Asset, Expected Amortization, Year One		10.4
Finite-Lived Intangible Asset, Expected Amortization, Year Two		9.8
Finite-Lived Intangible Asset, Expected Amortization, Year Three		9.7
Finite-Lived Intangible Asset, Expected Amortization, Year Four		9.1
Finite-Lived Intangible Asset, Expected Amortization, Year Five		$ 6.6
Customer-Related Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		14 years 3 months 18 days
Finite-Lived Intangible Assets, Gross		$ 53.6	35.4
Finite-Lived Intangible Assets, Accumulated Amortization		(5.8)	0.0
Finite-Lived Intangible Assets, Net		$ 47.8	35.4
Technology-Based Intangible Assets
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		9 years 3 months 18 days
Finite-Lived Intangible Assets, Gross		$ 36.6	25.9
Finite-Lived Intangible Assets, Accumulated Amortization		(9.4)	(5.4)
Finite-Lived Intangible Assets, Net		$ 27.2	20.5
Off-Market Favorable Lease
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life		10 years 9 months 18 days
Finite-Lived Intangible Assets, Gross		$ 35.9	31.6
Finite-Lived Intangible Assets, Accumulated Amortization		(15.4)	(12.9)
Finite-Lived Intangible Assets, Net		20.5	18.7
Railcar Leasing and Management Services Group [Member]
Goodwill [Line Items]
Goodwill		32.7	7.1
Goodwill, Acquired During Period		26.8
Goodwill, Written off Related to Sale of Business Unit		(1.2)
Rail Products Group [Member]
Goodwill [Line Items]
Goodwill		188.8	188.8
Goodwill, Acquired During Period		0.0
Goodwill, Written off Related to Sale of Business Unit		0.0
Trade Names
Finite-Lived Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)		11.2	4.4
Impairment of Intangible Assets, Indefinite-Lived (Excluding Goodwill)		$ 0.0	$ 0.0