Financial Data of Business Segments (Details) € in Millions, $ in Millions			3 Months Ended			6 Months Ended
	Dec. 29, 2020 USD ($)	Dec. 29, 2020 EUR (€)	Jun. 30, 2021 USD ($) AircraftEngines	Mar. 31, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) AircraftEngines	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			$ (50.0)		$ (47.4)	$ (103.6)	$ (92.9)
Provision for Income Taxes, Equity Method Investment			45.0		4.8	46.8	9.1
Lease Income			287.6		269.3	568.2	540.0
Marine operating revenue			5.1		3.3	8.7	6.6
Other Operating Income			24.4		27.9	46.0	53.3
Total Revenues			317.1		300.5	622.9	599.9
Cost of Property Repairs and Maintenance			76.6		82.3	150.9	168.1
Marine operating expense			5.5		3.2	10.1	7.3
Depreciation			91.5		81.6	180.1	162.0
Operating lease expense			10.2		12.5	21.1	25.8
Other operating expense			11.4		9.2	21.6	17.7
Total Expenses			195.2		188.8	383.8	380.9
Net gain on asset dispositions			34.7		6.0	57.2	33.4
Other (expense) income			(8.1)		(3.0)	(9.4)	(11.0)
Share of affiliates' earnings (pre-tax)			13.4		22.6	22.4	46.4
Segment profit (loss)			111.9		89.9	205.7	194.9
Net loss from discontinued operations, net of taxes			0.0		2.3	0.0	1.4
Disposition Gains on Owned Assets			32.2		4.5	48.5	31.4
Nonoperating Income, Residual Sharing Income			1.0		0.6	1.7	1.2
Nonremarketing Disposition Gain (Loss)			1.5		0.9	7.0	0.8
Net income			5.5		39.3	42.0	85.6
Net Income			5.5		37.0	42.0	84.2
Income tax benefit			13.6		4.7	22.0	17.8
Selling, general and administrative			47.8		43.4	94.9	83.8
Portfolio Investments and Capital Additions			153.9		210.5	663.4	391.5
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			561.4			561.4		$ 584.7
Identifiable assets			9,400.5			9,400.5		8,937.6
Payments to Acquire Property, Plant, and Equipment						(663.4)	(391.5)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax					3.6		3.6
Income from Discontinued Operations, Net of Taxes			0.0		(1.3)	0.0	(2.2)
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			58.6		9.5	68.8	26.9
Other Business Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(1.9)		1.6	(3.2)	2.9
Lease Income			6.1		0.0	9.7	0.0
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			2.3		0.0	3.4	0.0
Total Revenues			8.4		0.0	13.1	0.0
Cost of Property Repairs and Maintenance			0.9		0.0	1.4	0.0
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			2.9		0.0	4.8	0.0
Operating lease expense			0.0		0.0	0.0	0.0
Other operating expense			0.9		0.0	1.3	0.0
Total Expenses			4.7		0.0	7.5	0.0
Net gain on asset dispositions			0.3		0.0	0.4	0.0
Other (expense) income			(7.3)		(1.0)	(7.8)	(2.7)
Share of affiliates' earnings (pre-tax)			0.0		0.0	0.0	0.0
Segment profit (loss)			(5.2)		0.6	(5.0)	0.2
Disposition Gains on Owned Assets			0.3		0.0	0.3	0.0
Nonoperating Income, Residual Sharing Income			0.0		0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)			0.0		0.0	0.1	0.0
Portfolio Investments and Capital Additions			6.2		1.0	9.7	1.5
Identifiable assets			673.9			673.9		541.3
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(32.6)		(34.5)	(69.6)	(67.8)
Lease Income			204.2		210.0	411.0	422.1
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			19.2		25.5	37.0	49.1
Total Revenues			223.4		235.5	448.0	471.2
Cost of Property Repairs and Maintenance			61.5		70.4	119.9	143.3
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			65.2		64.4	130.9	128.0
Operating lease expense			10.2		12.5	21.1	25.8
Other operating expense			8.4		7.6	16.0	14.2
Total Expenses			145.3		154.9	287.9	311.3
Net gain on asset dispositions			33.1		5.2	54.6	32.0
Other (expense) income			(1.0)		(1.3)	(1.8)	(2.1)
Share of affiliates' earnings (pre-tax)			0.0		0.0	0.0	0.0
Segment profit (loss)			77.6		50.0	143.3	122.0
Disposition Gains on Owned Assets			31.5		4.4	47.8	31.3
Nonoperating Income, Residual Sharing Income			0.5		0.1	0.6	0.2
Nonremarketing Disposition Gain (Loss)			1.1		0.7	6.2	0.5
Portfolio Investments and Capital Additions			106.4		159.6	215.5	270.5
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			0.4			0.4		0.0
Identifiable assets			5,955.2			5,955.2		5,944.4
Rail International [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(11.1)		(11.5)	(23.3)	(22.1)
Lease Income			69.0		59.1	135.9	117.4
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			2.7		2.1	5.2	3.9
Total Revenues			71.7		61.2	141.1	121.3
Cost of Property Repairs and Maintenance			14.2		11.9	29.6	24.8
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			18.4		15.8	36.7	31.3
Operating lease expense			0.0		0.0	0.0	0.0
Other operating expense			1.7		1.5	3.7	3.3
Total Expenses			34.3		29.2	70.0	59.4
Net gain on asset dispositions			0.8		0.2	1.1	0.3
Other (expense) income			0.2		(0.7)	0.2	(6.2)
Share of affiliates' earnings (pre-tax)			0.0		0.0	0.0	0.0
Segment profit (loss)			27.3		20.0	49.1	33.9
Disposition Gains on Owned Assets			0.4		0.0	0.4	0.0
Nonoperating Income, Residual Sharing Income			0.0		0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)			0.4		0.2	0.7	0.3
Portfolio Investments and Capital Additions			40.8		49.9	85.2	119.2
Identifiable assets			1,731.9			1,731.9		1,745.8
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(4.4)		(3.0)	(7.5)	(5.9)
Lease Income			8.3		0.2	11.6	0.5
Marine operating revenue			5.1		3.3	8.7	6.6
Other Operating Income			0.2		0.3	0.4	0.3
Total Revenues			13.6		3.8	20.7	7.4
Cost of Property Repairs and Maintenance			0.0		0.0	0.0	0.0
Marine operating expense			5.5		3.2	10.1	7.3
Depreciation			5.0		1.4	7.7	2.7
Operating lease expense			0.0		0.0	0.0	0.0
Other operating expense			0.4		0.1	0.6	0.2
Total Expenses			10.9		4.7	18.4	10.2
Net gain on asset dispositions			0.5		0.6	1.1	1.1
Other (expense) income			0.0		0.0	0.0	0.0
Share of affiliates' earnings (pre-tax)			13.4		22.6	22.4	46.4
Segment profit (loss)			12.2		19.3	18.3	38.8
Disposition Gains on Owned Assets			0.0		0.1	0.0	0.1
Nonoperating Income, Residual Sharing Income			0.5		0.5	1.1	1.0
Nonremarketing Disposition Gain (Loss)			0.0		0.0	0.0	0.0
Portfolio Investments and Capital Additions			0.5		$ 0.0	353.0	$ 0.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			561.0			561.0		584.7
Identifiable assets			$ 1,039.5			$ 1,039.5		$ 706.1
Number of aircraft engines | AircraftEngines			14			14
Number of Specialized Gas Vessels | AircraftEngines			5			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