Financial Data of Business Segments (Details) € in Millions, $ in Millions			3 Months Ended			9 Months Ended
	Dec. 29, 2020 USD ($)	Dec. 29, 2020 EUR (€)	Sep. 30, 2021 USD ($) AircraftEngines	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) AircraftEngines	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			$ (49.8)		$ (48.6)	$ (153.4)	$ (141.5)
Provision for Income Taxes, Equity Method Investment			1.0		24.0	47.8	33.1
Lease Income			283.9		273.3	852.1	813.3
Marine operating revenue			5.0		5.0	13.7	11.6
Other Operating Income			24.6		26.1	70.6	79.4
Total Revenues			313.5		304.4	936.4	904.3
Cost of Property Repairs and Maintenance			74.2		76.7	225.1	244.8
Marine operating expense			3.7		3.6	13.8	10.9
Depreciation			91.1		83.4	271.2	245.4
Operating Lease, Expense			9.0		12.3	30.1	38.1
Other operating expense			9.7		8.3	31.3	26.0
Total Expenses			187.7		184.3	571.5	565.2
Net gain on asset dispositions			21.9		8.9	79.1	42.3
Other (expense) income			(0.3)		(1.2)	(9.7)	(12.2)
Share of affiliates' earnings (pre-tax)			3.8		46.8	26.2	93.2
Segment profit (loss)			101.4		126.0	307.1	320.9
Net loss from discontinued operations, net of taxes			0.0		(0.3)	0.0	1.1
Disposition Gains on Owned Assets			14.9		8.0	63.4	39.4
Nonoperating Income, Residual Sharing Income			0.8		0.6	2.5	1.8
Nonremarketing Disposition Gain (Loss)			6.2		0.3	13.2	1.1
Net income			40.1		47.9	82.1	133.5
Net Income			40.1		48.2	82.1	132.4
Income tax benefit			14.4		11.8	36.4	29.6
Selling, general and administrative			45.9		42.0	140.8	125.8
Portfolio Investments and Capital Additions			229.8		249.9	893.2	641.4
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			564.4			564.4		$ 584.7
Identifiable assets			9,586.3			9,586.3		8,937.6
Payments to Acquire Businesses, Gross	$ 203.2
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax					(0.3)		3.3
(Loss) Income from Discontinued Operations, Net of Taxes			0.0		0.0	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 | €		€ 165
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit			15.4		35.8	84.2	62.7
Other Business Segments [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(1.5)		2.2	(4.7)	5.1
Lease Income			6.5		0.0	16.2	0.0
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			2.4		0.0	5.8	0.0
Total Revenues			8.9		0.0	22.0	0.0
Cost of Property Repairs and Maintenance			1.3		0.0	2.7	0.0
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			2.9		0.0	7.7	0.0
Operating Lease, Expense			0.0		0.0	0.0	0.0
Other operating expense			0.7		0.0	2.0	0.0
Total Expenses			4.9		0.0	12.4	0.0
Net gain on asset dispositions			0.2		0.0	0.6	0.0
Other (expense) income			(1.0)		(0.6)	(8.8)	(3.3)
Share of affiliates' earnings (pre-tax)			0.0		0.0	0.0	0.0
Segment profit (loss)			1.7		1.6	(3.3)	1.8
Disposition Gains on Owned Assets			0.2		0.0	0.5	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			10.0		0.5	19.7	2.0
Identifiable assets			807.4			807.4		541.3
Rail North America [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(32.9)		(35.7)	(102.5)	(103.5)
Lease Income			200.4		208.7	611.4	630.8
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			19.4		23.4	56.4	72.5
Total Revenues			219.8		232.1	667.8	703.3
Cost of Property Repairs and Maintenance			58.9		63.2	178.8	206.5
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			64.8		65.0	195.7	193.0
Operating Lease, Expense			9.0		12.3	30.1	38.1
Other operating expense			6.6		6.6	22.6	20.8
Total Expenses			139.3		147.1	427.2	458.4
Net gain on asset dispositions			20.2		7.9	74.8	39.9
Other (expense) income			(1.1)		(1.1)	(2.9)	(3.2)
Share of affiliates' earnings (pre-tax)			(0.2)		0.0	(0.2)	0.0
Segment profit (loss)			66.5		56.1	209.8	178.1
Disposition Gains on Owned Assets			14.4		7.8	62.2	39.1
Nonoperating Income, Residual Sharing Income			0.2		0.1	0.8	0.3
Nonremarketing Disposition Gain (Loss)			5.6		0.0	11.8	0.5
Portfolio Investments and Capital Additions			178.9		204.1	394.4	474.6
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			0.2			0.2		0.0
Identifiable assets			6,016.0			6,016.0		5,944.4
Rail International [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(10.9)		(11.9)	(34.2)	(34.0)
Lease Income			68.8		64.5	204.7	181.9
Marine operating revenue			0.0		0.0	0.0	0.0
Other Operating Income			2.7		2.6	7.9	6.5
Total Revenues			71.5		67.1	212.6	188.4
Cost of Property Repairs and Maintenance			14.0		13.5	43.6	38.3
Marine operating expense			0.0		0.0	0.0	0.0
Depreciation			18.5		17.1	55.2	48.4
Operating Lease, Expense			0.0		0.0	0.0	0.0
Other operating expense			1.8		1.6	5.5	4.9
Total Expenses			34.3		32.2	104.3	91.6
Net gain on asset dispositions			0.9		0.5	2.0	0.8
Other (expense) income			(0.2)		0.5	0.0	(5.7)
Share of affiliates' earnings (pre-tax)			0.0		0.0	0.0	0.0
Segment profit (loss)			27.0		24.0	76.1	57.9
Disposition Gains on Owned Assets			0.3		0.2	0.7	0.2
Nonoperating Income, Residual Sharing Income			0.0		0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)			0.6		0.3	1.3	0.6
Portfolio Investments and Capital Additions			40.9		45.3	126.1	164.5
Identifiable assets			1,732.8			1,732.8		1,745.8
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Interest expense, net			(4.5)		(3.2)	(12.0)	(9.1)
Lease Income			8.2		0.1	19.8	0.6
Marine operating revenue			5.0		5.0	13.7	11.6
Other Operating Income			0.1		0.1	0.5	0.4
Total Revenues			13.3		5.2	34.0	12.6
Cost of Property Repairs and Maintenance			0.0		0.0	0.0	0.0
Marine operating expense			3.7		3.6	13.8	10.9
Depreciation			4.9		1.3	12.6	4.0
Operating Lease, Expense			0.0		0.0	0.0	0.0
Other operating expense			0.6		0.1	1.2	0.3
Total Expenses			9.2		5.0	27.6	15.2
Net gain on asset dispositions			0.6		0.5	1.7	1.6
Other (expense) income			2.0		0.0	2.0	0.0
Share of affiliates' earnings (pre-tax)			4.0		46.8	26.4	93.2
Segment profit (loss)			6.2		44.3	24.5	83.1
Disposition Gains on Owned Assets			0.0		0.0	0.0	0.1
Nonoperating Income, Residual Sharing Income			0.6		0.5	1.7	1.5
Nonremarketing Disposition Gain (Loss)			0.0		0.0	0.0	0.0
Portfolio Investments and Capital Additions			0.0		$ 0.0	353.0	$ 0.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures			564.2			564.2		584.7
Identifiable assets			$ 1,030.1			$ 1,030.1		$ 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