Financial Data of Business Segments (Details)	3 Months Ended
	Mar. 31, 2024 USD ($) Segment	Mar. 31, 2023 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net Income (Loss) Attributable to Parent	$ 74,300,000	$ 77,400,000
Provision for Income Taxes, Equity Method Investment	4,200,000	6,900,000
Lease Income	333,300,000	302,000,000.0
Marine operating revenue	0	3,500,000
Other Operating Income	33,400,000	28,900,000
Total Revenues	379,900,000	338,900,000
Marine operating expense	0	2,000,000.0
Depreciation	96,000,000.0	89,800,000
Operating Lease, Expense	9,000,000.0	9,000,000.0
Other operating expense	13,600,000	11,000,000.0
Total Expenses	210,000,000.0	195,700,000
Gain (Loss) on Disposition of Assets, Net	36,200,000	47,100,000
Interest expense, net	(77,800,000)	(59,000,000.0)
Other (expense) income	800,000	(4,000,000.0)
Share of affiliates' earnings (pre-tax)	23,900,000	27,600,000
Segment profit (loss)	153,000,000.0	154,900,000
Income tax benefit	18,600,000	20,200,000
Selling, general and administrative	55,900,000	50,400,000
Disposition Gains on Owned Assets	33,700,000	44,700,000
Nonoperating Income, Residual Sharing Income	100,000	200,000
Nonremarketing Disposition Gain (Loss)	2,400,000	3,400,000
Portfolio Investments and Capital Additions	378,600,000	387,000,000.0
Identifiable assets	11,579,100,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(647,600,000)		$ (627,000,000.0)
Assets	$ (11,579,100,000)		(11,326,000,000)
Number of business segments | Segment	3
Asset Impairment Charges	$ 0	1,200,000
Non-dedicated engine revenue	13,200,000	4,500,000
Maintenance Expense	91,400,000	83,900,000
Interest Income (Expense), Net	(77,800,000)	(59,000,000.0)
Net gain on asset dispositions	36,200,000	47,100,000
Rolls Royce
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payment for Management Fee	600,000	500,000
Payment for Management Fee	600,000	500,000
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	22,800,000	27,100,000
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	236,500,000	215,100,000
Marine operating revenue		0
Other Operating Income	28,500,000	23,800,000
Total Revenues	265,000,000.0	238,900,000
Marine operating expense		0
Depreciation	65,100,000	65,500,000
Operating Lease, Expense	9,000,000.0	9,000,000.0
Other operating expense	6,700,000	7,000,000.0
Total Expenses	153,700,000	148,400,000
Gain (Loss) on Disposition of Assets, Net	34,200,000	47,800,000
Other (expense) income	(2,100,000)	(400,000)
Share of affiliates' earnings (pre-tax)	200,000	(400,000)
Segment profit (loss)	90,300,000	95,200,000
Disposition Gains on Owned Assets	32,900,000	44,700,000
Nonoperating Income, Residual Sharing Income	100,000	100,000
Nonremarketing Disposition Gain (Loss)	1,200,000	3,000,000.0
Portfolio Investments and Capital Additions	321,700,000	296,500,000
Identifiable assets	7,245,600,000		6,993,800,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(400,000)		200,000
Asset Impairment Charges		0
Maintenance Expense	72,900,000	66,900,000
Interest Income (Expense), Net	(53,300,000)	(42,300,000)
Net gain on asset dispositions	34,200,000	47,800,000
Rail International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	80,600,000	70,400,000
Marine operating revenue		0
Other Operating Income	3,100,000	2,900,000
Total Revenues	83,700,000	73,300,000
Marine operating expense		0
Depreciation	18,900,000	15,700,000
Operating Lease, Expense	0	0
Other operating expense	3,500,000	2,200,000
Total Expenses	39,900,000	33,800,000
Gain (Loss) on Disposition of Assets, Net	1,300,000	800,000
Other (expense) income	400,000	(4,300,000)
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	28,800,000	23,500,000
Disposition Gains on Owned Assets	100,000	400,000
Nonoperating Income, Residual Sharing Income	0	0
Nonremarketing Disposition Gain (Loss)	1,200,000	400,000
Portfolio Investments and Capital Additions	49,900,000	81,100,000
Identifiable assets	2,215,100,000		2,175,200,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Asset Impairment Charges		0
Gain (Loss) on Disposition of Business		300,000
Maintenance Expense	17,500,000	15,900,000
Interest Income (Expense), Net	(16,700,000)	(12,500,000)
Net gain on asset dispositions	1,300,000	800,000
Gain (Loss) on Disposition of Business		300,000
Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8,100,000	8,200,000
Marine operating revenue		0
Other Operating Income	1,800,000	2,200,000
Total Revenues	9,900,000	10,400,000
Marine operating expense		0
Depreciation	3,600,000	3,200,000
Operating Lease, Expense	0	0
Other operating expense	900,000	900,000
Total Expenses	5,500,000	5,200,000
Gain (Loss) on Disposition of Assets, Net	100,000	0
Other (expense) income	2,200,000	1,200,000
Share of affiliates' earnings (pre-tax)	0	0
Segment profit (loss)	8,200,000	7,900,000
Disposition Gains on Owned Assets	100,000	0
Nonoperating Income, Residual Sharing Income	0	0
Nonremarketing Disposition Gain (Loss)	0	0
Portfolio Investments and Capital Additions	7,000,000.0	9,400,000
Identifiable assets	742,300,000		801,900,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Asset Impairment Charges		0
Maintenance Expense	1,000,000.0	1,100,000
Interest Income (Expense), Net	1,500,000	1,500,000
Net gain on asset dispositions	100,000	0
Engine Leasing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8,100,000	8,300,000
Marine operating revenue		3,500,000
Other Operating Income	0	0
Total Revenues	21,300,000	16,300,000
Marine operating expense		2,000,000.0
Depreciation	8,400,000	5,400,000
Operating Lease, Expense	0	0
Other operating expense	2,500,000	900,000
Total Expenses	10,900,000	8,300,000
Gain (Loss) on Disposition of Assets, Net	600,000	(1,500,000)
Other (expense) income	300,000	(500,000)
Share of affiliates' earnings (pre-tax)	23,700,000	28,000,000.0
Segment profit (loss)	25,700,000	28,300,000
Disposition Gains on Owned Assets	600,000	(400,000)
Nonoperating Income, Residual Sharing Income	0	100,000
Nonremarketing Disposition Gain (Loss)	0	0
Portfolio Investments and Capital Additions	0	0
Identifiable assets	1,376,100,000		1,355,100,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(647,200,000)		$ 626,800,000
Asset Impairment Charges		1,200,000
Non-dedicated engine revenue	13,200,000	4,500,000
Maintenance Expense	0	0
Interest Income (Expense), Net	(9,300,000)	(5,700,000)
Net gain on asset dispositions	$ 600,000	$ (1,500,000)