Partially-Owned Leasing Subsidiaries - Narrative (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($) subsidiary board_member
Partially-owned subsidiaries
Noncontrolling Interest [Line Items]
Parent Company Guarantees | $	$ 0.0
Railcar Leasing and Management Services Group [Member] | Partially-owned subsidiaries
Noncontrolling Interest [Line Items]
Number of Subsidiaries | subsidiary	2
Number of Board Members | board_member	7
Number of Board Members of Subsidiary, Designated by Parent | board_member	2
Partially-owned subsidiaries | Railcar Leasing and Management Services Group [Member]
Noncontrolling Interest [Line Items]
Carrying Value of Investment In Partially-Owned Consolidated Subsidiary | $	$ 140.3
Noncontrolling Interest, Ownership Percentage by Parent	38.00%
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners	62.00%