Financial Data of Business Segments (Details)	3 Months Ended			6 Months Ended
	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2024 USD ($) Segment	Jun. 30, 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	$ 44,400,000	$ 63,300,000		$ 118,700,000	$ 140,700,000
Provision for Income Taxes, Equity Method Investment	4,100,000	6,300,000		8,300,000	13,200,000
Lease Income	339,600,000	308,600,000		672,900,000	610,600,000
Marine operating revenue	0	2,000,000.0		0	5,500,000
Other Operating Income	33,400,000	26,200,000		66,800,000	55,100,000
Total Revenues	386,700,000	343,200,000		766,600,000	682,100,000
Marine operating expense	0	2,400,000		0	4,400,000
Depreciation	98,500,000	92,100,000		194,500,000	181,900,000
Operating Lease, Expense	9,000,000.0	9,000,000.0		18,000,000.0	18,000,000.0
Other operating expense	13,800,000	11,000,000.0		27,400,000	22,000,000.0
Total Expenses	217,900,000	196,800,000		427,900,000	392,500,000
Gain (Loss) on Disposition of Assets, Net	25,600,000	41,100,000		61,800,000	88,200,000
Interest expense, net	(82,800,000)	(63,700,000)		(160,600,000)	(122,700,000)
Other (expense) income	(10,800,000)	(4,900,000)		(10,000,000.0)	(8,900,000)
Share of affiliates' earnings (pre-tax)	16,700,000	20,300,000		40,600,000	47,900,000
Segment profit (loss)	117,500,000	139,200,000		270,500,000	294,100,000
Income tax benefit	10,400,000	17,600,000		29,000,000.0	37,800,000
Selling, general and administrative	58,600,000	52,000,000.0		114,500,000	102,400,000
Disposition Gains on Owned Assets	19,800,000	36,900,000		53,500,000	81,600,000
Nonoperating Income, Residual Sharing Income	100,000	200,000		200,000	400,000
Nonremarketing Disposition Gain (Loss)	5,700,000	4,000,000.0		8,100,000	7,400,000
Portfolio Investments and Capital Additions	442,000,000.0	486,600,000		820,600,000	873,600,000
Identifiable assets	12,222,600,000			12,222,600,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(660,800,000)			(660,800,000)		$ (627,000,000.0)
Assets	(12,222,600,000)			$ (12,222,600,000)		(11,326,000,000)
Number of business segments | Segment				3
Asset Impairment Charges				$ 0	1,200,000
Non-dedicated engine revenue	13,700,000	6,400,000		26,900,000	10,900,000
Maintenance Expense	96,600,000	82,300,000		188,000,000.0	166,200,000
Interest Income (Expense), Net	(82,800,000)	(63,700,000)		(160,600,000)	(122,700,000)
Net gain on asset dispositions	25,600,000	41,100,000		61,800,000	88,200,000
Rolls Royce
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payment for Management Fee	900,000	500,000		1,800,000	1,000,000
Payment for Management Fee	900,000	500,000		1,800,000	1,000,000
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	14,500,000	23,900,000		37,300,000	51,000,000.0
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	242,100,000	218,900,000		478,600,000	434,000,000.0
Marine operating revenue		0			0
Other Operating Income	28,300,000	21,500,000		56,800,000	45,300,000
Total Revenues	270,400,000	240,400,000		535,400,000	479,300,000
Marine operating expense		0			0
Depreciation	66,800,000	66,100,000		131,900,000	131,600,000
Operating Lease, Expense	9,000,000.0	9,000,000.0		18,000,000.0	18,000,000.0
Other operating expense	6,400,000	6,700,000		13,100,000	13,700,000
Total Expenses	159,600,000	148,600,000		313,300,000	297,000,000.0
Gain (Loss) on Disposition of Assets, Net	24,900,000	34,100,000		59,100,000	81,900,000
Other (expense) income	(300,000)	(2,100,000)		(2,400,000)	(2,500,000)
Share of affiliates' earnings (pre-tax)	(200,000)	0		0	(400,000)
Segment profit (loss)	78,800,000	79,300,000		169,100,000	174,500,000
Disposition Gains on Owned Assets	19,800,000	30,700,000		52,700,000	75,400,000
Nonoperating Income, Residual Sharing Income	100,000	100,000		200,000	200,000
Nonremarketing Disposition Gain (Loss)	5,000,000.0	3,300,000		6,200,000	6,300,000
Portfolio Investments and Capital Additions	308,100,000	161,300,000		629,800,000	457,800,000
Identifiable assets	7,427,500,000			7,427,500,000		6,993,800,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(200,000)			(200,000)		200,000
Asset Impairment Charges					0
Maintenance Expense	77,400,000	66,800,000		150,300,000	133,700,000
Interest Income (Expense), Net	(56,400,000)	(44,500,000)		(109,700,000)	(86,800,000)
Net gain on asset dispositions	24,900,000	34,100,000		59,100,000	81,900,000
Rail International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	82,000,000.0	73,100,000		162,600,000	143,500,000
Marine operating revenue		0			0
Other Operating Income	3,200,000	3,100,000		6,300,000	6,000,000.0
Total Revenues	85,200,000	76,200,000		168,900,000	149,500,000
Marine operating expense		0			0
Depreciation	19,400,000	16,600,000		38,300,000	32,300,000
Operating Lease, Expense	0	0		0	0
Other operating expense	3,600,000	2,300,000		7,100,000	4,500,000
Total Expenses	41,200,000	33,500,000		81,100,000	67,300,000
Gain (Loss) on Disposition of Assets, Net	700,000	700,000		2,000,000.0	1,500,000
Other (expense) income	(700,000)	(2,600,000)		(300,000)	(6,900,000)
Share of affiliates' earnings (pre-tax)	0	0		0	0
Segment profit (loss)	26,500,000	27,300,000		55,300,000	50,800,000
Disposition Gains on Owned Assets	0	100,000		100,000	500,000
Nonoperating Income, Residual Sharing Income	0	0		0	0
Nonremarketing Disposition Gain (Loss)	700,000	600,000		1,900,000	1,000,000.0
Portfolio Investments and Capital Additions	59,600,000	77,300,000		109,500,000	158,400,000
Identifiable assets	2,237,000,000			2,237,000,000		2,175,200,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0			0
Asset Impairment Charges					0
Gain (Loss) on Disposition of Business			$ 300,000
Maintenance Expense	18,200,000	14,600,000		35,700,000	30,500,000
Interest Income (Expense), Net	(17,500,000)	(13,500,000)		(34,200,000)	(26,000,000.0)
Net gain on asset dispositions	700,000	700,000		2,000,000.0	1,500,000
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	7,400,000	8,500,000		15,500,000	16,700,000
Marine operating revenue		0			0
Other Operating Income	1,900,000	1,600,000		3,700,000	3,800,000
Total Revenues	9,300,000	10,100,000		19,200,000	20,500,000
Marine operating expense		0		0	0
Depreciation	3,700,000	3,300,000		7,300,000	6,500,000
Operating Lease, Expense	0	0			0
Other operating expense	1,900,000	600,000		2,800,000	1,500,000
Total Expenses	6,600,000	4,800,000		12,100,000	10,000,000.0
Gain (Loss) on Disposition of Assets, Net	0	300,000		100,000	300,000
Other (expense) income	(9,700,000)	(400,000)		(7,500,000)	800,000
Share of affiliates' earnings (pre-tax)	0	0		0	0
Segment profit (loss)	(6,200,000)	6,000,000.0		2,000,000.0	13,900,000
Disposition Gains on Owned Assets	0	200,000		100,000	200,000
Nonoperating Income, Residual Sharing Income	0	0		0	0
Nonremarketing Disposition Gain (Loss)	0	100,000		0	100,000
Portfolio Investments and Capital Additions	3,000,000.0	9,000,000.0		10,000,000.0	18,400,000
Identifiable assets	1,116,100,000			1,116,100,000		801,900,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0			0
Asset Impairment Charges					0
Maintenance Expense	1,000,000.0	900,000		2,000,000.0	2,000,000.0
Interest Income (Expense), Net	800,000	800,000		2,300,000	2,300,000
Net gain on asset dispositions	0	300,000		100,000	300,000
Engine Leasing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8,100,000	8,100,000		16,200,000	16,400,000
Marine operating revenue		2,000,000.0			5,500,000
Other Operating Income	0	0		0	0
Total Revenues	21,800,000	16,500,000		43,100,000	32,800,000
Marine operating expense		2,400,000			4,400,000
Depreciation	8,600,000	6,100,000		17,000,000.0	11,500,000
Operating Lease, Expense	0	0		0	0
Other operating expense	1,900,000	1,400,000		4,400,000	2,300,000
Total Expenses	10,500,000	9,900,000		21,400,000	18,200,000
Gain (Loss) on Disposition of Assets, Net	0	6,000,000.0		600,000	4,500,000
Other (expense) income	(100,000)	200,000		200,000	(300,000)
Share of affiliates' earnings (pre-tax)	16,900,000	20,300,000		40,600,000	48,300,000
Segment profit (loss)	18,400,000	26,600,000		44,100,000	54,900,000
Disposition Gains on Owned Assets	0	5,900,000		600,000	5,500,000
Nonoperating Income, Residual Sharing Income	0	100,000		0	200,000
Nonremarketing Disposition Gain (Loss)	0	0		0	0
Portfolio Investments and Capital Additions	71,300,000	239,000,000.0		71,300,000	239,000,000.0
Identifiable assets	1,442,000,000			1,442,000,000		1,355,100,000
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(660,600,000)			(660,600,000)		$ 626,800,000
Asset Impairment Charges					1,200,000
Non-dedicated engine revenue	13,700,000	6,400,000		26,900,000	10,900,000
Maintenance Expense	0	0		0	0
Interest Income (Expense), Net	(9,700,000)	(6,500,000)		(19,000,000.0)	(12,200,000)
Net gain on asset dispositions	$ 0	$ 6,000,000.0		$ 600,000	$ 4,500,000