Summary of Significant Accounting Policies Goodwill (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 222.7	$ 195.9
Railcar Leasing and Management Services Group [Member]
Goodwill [Line Items]
Goodwill	33.9	7.1
Rail Products Group [Member]
Goodwill [Line Items]
Goodwill	$ 188.8	$ 188.8