Financial Data of Busines Segments (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	$ 1,251,400,000	$ 1,154,600,000	$ 1,140,500,000
MarineOperatingRevenue	6,900,000	18,900,000	19,100,000
Other revenue	115,000,000.0	98,000,000.0	97,800,000
Total Revenues	1,410,900,000	1,273,000,000	1,257,400,000
Maintenance Expense	344,800,000	292,700,000	297,100,000
Marine operating expense	6,500,000	14,100,000	17,500,000
Depreciation	376,300,000	357,500,000	364,400,000
Operating Lease, Expense	36,000,000.0	36,100,000	39,200,000
Other operating expense	46,600,000	37,400,000	44,000,000.0
Total Expenses	810,200,000	737,800,000	762,200,000
Net gain on asset dispositions	130,300,000	77,900,000	105,900,000
Interest Income (Expense), Net	(263,400,000)	(214,000,000.0)	(204,000,000.0)
Other (expense) income	(9,400,000)	(27,000,000.0)	(3,700,000)
Share of affiliates' earnings (pre-tax)	98,100,000	45,900,000	56,500,000
Segment Profit Loss	556,300,000	418,000,000.0	449,900,000
Selling, general and administrative	212,700,000	195,000,000.0	198,300,000
Income tax benefit	58,700,000	54,800,000	53,200,000
Net Income	259,200,000	155,900,000	143,100,000
Disposition Gains on Owned Assets	119,800,000	104,100,000	82,400,000
Nonoperating Income, Residual Sharing Income	900,000	5,600,000	8,900,000
Asset Impairment Charges	(1,500,000)	(48,900,000)	(2,400,000)
Identifiable assets	11,326,000,000	10,072,000,000	9,541,700,000
Nonremarketing Disposition Gain (Loss)	11,100,000	17,100,000	17,000,000.0
Portfolio Investments and Capital Additions	1,665,000,000	1,255,800,000	1,131,900,000
Investments in Affiliated Companies	627,000,000.0	575,100,000	588,400,000
Assets of Continuing Operations	11,326,000,000	10,072,000,000
Payments to Acquire Property, Plant, and Equipment	(1,665,000,000)	(1,255,800,000)	(1,130,100,000)
Provision for Income Taxes, Equity Method Investment	25,700,000	12,300,000	55,300,000
Non-dedicated engine revenue	37,600,000	1,500,000	0
Net gain on asset dispositions	130,300,000	77,900,000	105,900,000
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	84,400,000	67,100,000	108,500,000
Other Business Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	33,400,000	29,400,000	25,000,000.0
MarineOperatingRevenue	0	0	0
Other revenue	8,100,000	6,700,000	8,700,000
Total Revenues	41,500,000	36,100,000	33,700,000
Maintenance Expense	4,100,000	2,800,000	4,100,000
Marine operating expense	0	0	0
Depreciation	13,900,000	12,000,000.0	12,100,000
Operating Lease, Expense	0	0	0
Other operating expense	3,000,000.0	2,300,000	3,000,000.0
Total Expenses	21,000,000.0	17,100,000	19,200,000
Net gain on asset dispositions	600,000	500,000	900,000
Interest Income (Expense), Net	5,500,000	(4,800,000)	(6,000,000.0)
Other (expense) income	2,600,000	(18,600,000)	(10,700,000)
Share of affiliates' earnings (pre-tax)	0	0	0
Segment Profit Loss	29,200,000	(3,900,000)	(1,300,000)
Disposition Gains on Owned Assets	300,000	300,000	500,000
Nonoperating Income, Residual Sharing Income	0	0	0
Asset Impairment Charges	0	0	0
Identifiable assets			621,400,000
Nonremarketing Disposition Gain (Loss)	300,000	200,000	400,000
Portfolio Investments and Capital Additions	38,400,000	46,300,000	31,200,000
Investments in Affiliated Companies	0	0	0
Assets of Continuing Operations	801,900,000	745,300,000
Net gain on asset dispositions	600,000	500,000	900,000
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	888,800,000	826,000,000.0	814,500,000
MarineOperatingRevenue	0	0	0
Other revenue	93,900,000	82,000,000.0	77,200,000
Total Revenues	982,700,000	908,000,000.0	891,700,000
Maintenance Expense	276,600,000	238,500,000	235,400,000
Marine operating expense	0	0	0
Depreciation	265,900,000	258,600,000	261,100,000
Operating Lease, Expense	36,000,000.0	36,100,000	39,200,000
Other operating expense	25,900,000	24,500,000	30,300,000
Total Expenses	604,400,000	557,700,000	566,000,000.0
Net gain on asset dispositions	120,500,000	119,700,000	94,300,000
Interest Income (Expense), Net	(182,900,000)	(144,600,000)	(136,200,000)
Other (expense) income	(8,000,000.0)	(4,600,000)	1,600,000
Share of affiliates' earnings (pre-tax)	(600,000)	500,000	0
Segment Profit Loss	307,300,000	321,300,000	285,400,000
Disposition Gains on Owned Assets	111,700,000	102,200,000	80,700,000
Nonoperating Income, Residual Sharing Income	400,000	2,400,000	900,000
Asset Impairment Charges	0	0	(2,400,000)
Identifiable assets			6,141,700,000
Nonremarketing Disposition Gain (Loss)	8,400,000	15,100,000	15,100,000
Portfolio Investments and Capital Additions	976,900,000	815,900,000	574,400,000
Investments in Affiliated Companies			300,000
Assets of Continuing Operations	6,993,800,000	6,445,700,000
Net gain on asset dispositions	120,500,000	119,700,000	94,300,000
Rail North America [Member] | RailPulse
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Investments in Affiliated Companies	200,000	800,000
Rail International [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	296,600,000	266,200,000	272,900,000
MarineOperatingRevenue	0	0	0
Other revenue	12,900,000	9,100,000	11,400,000
Total Revenues	309,500,000	275,300,000	284,300,000
Maintenance Expense	64,100,000	51,400,000	57,600,000
Marine operating expense	0	0	0
Depreciation	68,200,000	69,100,000	73,600,000
Operating Lease, Expense	0	0	0
Other operating expense	10,400,000	8,300,000	9,000,000.0
Total Expenses	142,700,000	128,800,000	140,200,000
Net gain on asset dispositions	7,000,000.0	(11,200,000)	2,700,000
Interest Income (Expense), Net	(56,200,000)	(45,600,000)	(45,200,000)
Other (expense) income	(4,200,000)	(3,800,000)	3,400,000
Share of affiliates' earnings (pre-tax)	0	0	0
Segment Profit Loss	113,400,000	85,900,000	105,000,000.0
Disposition Gains on Owned Assets	4,900,000	1,600,000	1,200,000
Nonoperating Income, Residual Sharing Income	0	0	0
Asset Impairment Charges	(300,000)	(14,600,000)	0
Identifiable assets			1,729,900,000
Nonremarketing Disposition Gain (Loss)	2,400,000	1,800,000	1,500,000
Portfolio Investments and Capital Additions	382,400,000	243,900,000	173,300,000
Investments in Affiliated Companies	0	0	0
Assets of Continuing Operations	2,175,200,000	1,774,400,000
Net gain on asset dispositions	7,000,000.0	(11,200,000)	2,700,000
Portfolio Management [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	32,600,000	33,000,000.0	28,100,000
MarineOperatingRevenue	6,900,000	18,900,000	19,100,000
Other revenue	100,000	200,000	500,000
Total Revenues	77,200,000	53,600,000	47,700,000
Maintenance Expense	0	0	0
Marine operating expense	6,500,000	14,100,000	17,500,000
Depreciation	28,300,000	17,800,000	17,600,000
Operating Lease, Expense	0	0	0
Other operating expense	7,300,000	2,300,000	1,700,000
Total Expenses	42,100,000	34,200,000	36,800,000
Net gain on asset dispositions	2,200,000	(31,100,000)	8,000,000.0
Interest Income (Expense), Net	(29,800,000)	(19,000,000.0)	(16,600,000)
Other (expense) income	200,000	0	2,000,000.0
Share of affiliates' earnings (pre-tax)	98,700,000	45,400,000	56,500,000
Segment Profit Loss	106,400,000	14,700,000	60,800,000
Disposition Gains on Owned Assets	2,900,000	0	0
Nonoperating Income, Residual Sharing Income	500,000	3,200,000	8,000,000.0
Asset Impairment Charges	(1,200,000)	(34,300,000)	0
Nonremarketing Disposition Gain (Loss)	0	0	0
Portfolio Investments and Capital Additions	267,300,000	149,700,000	353,000,000.0
Investments in Affiliated Companies		574,300,000	588,100,000
Assets of Continuing Operations	1,355,100,000	1,106,600,000	1,048,700,000
Non-dedicated engine revenue	37,600,000	1,500,000
Net gain on asset dispositions	2,200,000	(31,100,000)	$ 8,000,000.0
Portfolio Management [Member] | Rolls Royce Partners Finance [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Investments in Affiliated Companies	$ 626,800,000	$ 574,300,000