Financial Data of Business Segments (Details) € in Millions, $ in Millions			3 Months Ended
	Dec. 29, 2020 USD ($)	Dec. 29, 2020 EUR (€)	Mar. 31, 2021 USD ($) AircraftEngines	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			$ (53.6)	$ (45.5)
Provision for Income Taxes, Equity Method Investment			1.8	4.3
Lease Income			280.6	270.7
Marine operating revenue			3.6	3.3
Other Operating Income			21.6	25.4
Total Revenues			305.8	299.4
Cost of Property Repairs and Maintenance			74.3	85.8
Marine operating expense			4.6	4.1
Depreciation			88.6	80.4
Operating lease expense			10.9	13.3
Other operating expense			10.2	8.5
Total Expenses			188.6	192.1
Net gain on asset dispositions			22.5	27.4
Other (expense) income			(1.3)	(8.0)
Share of affiliates' earnings (pre-tax)			9.0	23.8
Segment profit (loss)			93.8	105.0
Income from Discontinued Operations, Net of Taxes			0.0	(0.9)
Disposition Gains on Owned Assets			16.3	26.9
Nonoperating Income, Residual Sharing Income			0.7	0.6
Nonremarketing Disposition Gain (Loss)			5.5	(0.1)
Net income			36.5	46.3
Net Income			36.5	47.2
Income tax benefit			8.4	13.1
Selling, general and administrative			47.1	40.4
Portfolio Investments and Capital Additions			509.5	181.0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			592.2		$ 584.7
Identifiable assets			9,915.3		8,937.6
Payments to Acquire Property, Plant, and Equipment			(509.5)	(181.0)
Trifleet Leasing Holding B.V.
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payments to Acquire Businesses, Gross	$ 203.2	€ 165
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit			10.2	17.4
Other Business Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(1.3)	1.3
Lease Income			3.6	0.0
Marine operating revenue			0.0	0.0
Other Operating Income			1.1	0.0
Total Revenues			4.7	0.0
Cost of Property Repairs and Maintenance			0.5	0.0
Marine operating expense			0.0	0.0
Depreciation			1.9	0.0
Operating lease expense			0.0	0.0
Other operating expense			0.4	0.0
Total Expenses			2.8	0.0
Net gain on asset dispositions			0.1	0.0
Other (expense) income			(0.5)	(1.7)
Share of affiliates' earnings (pre-tax)			0.0	0.0
Segment profit (loss)			0.2	(0.4)
Disposition Gains on Owned Assets			0.0	0.0
Nonoperating Income, Residual Sharing Income			0.0	0.0
Nonremarketing Disposition Gain (Loss)			0.1	0.0
Portfolio Investments and Capital Additions			3.5	0.5
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					0.0
Identifiable assets			1,217.4		541.3
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(37.0)	(33.3)
Lease Income			206.8	212.1
Marine operating revenue			0.0	0.0
Other Operating Income			17.8	23.6
Total Revenues			224.6	235.7
Cost of Property Repairs and Maintenance			58.4	72.9
Marine operating expense			0.0	0.0
Depreciation			65.7	63.6
Operating lease expense			10.9	13.3
Other operating expense			7.6	6.6
Total Expenses			142.6	156.4
Net gain on asset dispositions			21.5	26.8
Other (expense) income			(0.8)	(0.8)
Share of affiliates' earnings (pre-tax)			0.0	0.0
Segment profit (loss)			65.7	72.0
Disposition Gains on Owned Assets			16.3	26.9
Nonoperating Income, Residual Sharing Income			0.1	0.1
Nonremarketing Disposition Gain (Loss)			5.1	(0.2)
Portfolio Investments and Capital Additions			109.1	110.9
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			0.0		0.0
Identifiable assets			5,932.0		5,944.4
Rail International [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(12.2)	(10.6)
Lease Income			66.9	58.3
Marine operating revenue			0.0	0.0
Other Operating Income			2.5	1.8
Total Revenues			69.4	60.1
Cost of Property Repairs and Maintenance			15.4	12.9
Marine operating expense			0.0	0.0
Depreciation			18.3	15.5
Operating lease expense			0.0	0.0
Other operating expense			2.0	1.8
Total Expenses			35.7	30.2
Net gain on asset dispositions			0.3	0.1
Other (expense) income			0.0	(5.5)
Share of affiliates' earnings (pre-tax)			0.0	0.0
Segment profit (loss)			21.8	13.9
Disposition Gains on Owned Assets			0.0	0.0
Nonoperating Income, Residual Sharing Income			0.0	0.0
Nonremarketing Disposition Gain (Loss)			0.3	0.1
Portfolio Investments and Capital Additions			44.4	69.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures					0.0
Identifiable assets			1,698.9		1,745.8
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(3.1)	(2.9)
Lease Income			3.3	0.3
Marine operating revenue			3.6	3.3
Other Operating Income			0.2	0.0
Total Revenues			7.1	3.6
Cost of Property Repairs and Maintenance			0.0	0.0
Marine operating expense			4.6	4.1
Depreciation			2.7	1.3
Operating lease expense			0.0	0.0
Other operating expense			0.2	0.1
Total Expenses			7.5	5.5
Net gain on asset dispositions			0.6	0.5
Other (expense) income			0.0	0.0
Share of affiliates' earnings (pre-tax)			9.0	23.8
Segment profit (loss)			6.1	19.5
Disposition Gains on Owned Assets			0.0	0.0
Nonoperating Income, Residual Sharing Income			0.6	0.5
Nonremarketing Disposition Gain (Loss)			0.0	0.0
Portfolio Investments and Capital Additions			352.5	$ 0.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			592.2		584.7
Identifiable assets			$ 1,067.0		$ 706.1
Number of aircraft engines | AircraftEngines			14
Number of Specialized Gas Vessels | AircraftEngines			5
Portfolio Management | Rolls-Royce Aircraft Engines
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Payments to Acquire Property, Plant, and Equipment			$ 352.0