Financial Data of Business Segments (Details) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2022 USD ($) AircraftEngines	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) AircraftEngines	Jun. 30, 2022 USD ($) Segment AircraftEngines	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income	$ 2.6	$ 5.5		$ 78.4	$ 42.0
Provision for Income Taxes, Equity Method Investment	4.7	45.0		3.5	46.8
Lease Income	284.9	287.6		568.2	568.2
Marine operating revenue	5.2	5.1		11.4	8.7
Other Operating Income	22.6	24.4		49.7	46.0
Total Revenues	312.7	317.1		629.3	622.9
Cost of Property Repairs and Maintenance	70.8	76.6		145.4	150.9
Marine operating expense	3.9	5.5		8.1	10.1
Depreciation	90.0	91.5		179.5	180.1
Operating Lease, Expense	9.0	10.2		18.1	21.1
Other operating expense	9.3	11.4		20.0	21.6
Total Expenses	183.0	195.2		371.1	383.8
Gain (Loss) on Disposition of Assets, Net	(24.2)	34.7		49.5	57.2
Interest expense, net	(51.9)	(50.0)		(103.1)	(103.6)
Other (expense) income	(11.3)	(8.1)		(13.3)	(9.4)
Share of affiliates' earnings (pre-tax)	15.6	13.4		10.8	22.4
Segment profit (loss)	57.9	111.9		202.1	205.7
Income tax benefit	2.7	13.6		25.1	22.0
Selling, general and administrative	47.9	47.8		95.1	94.9
Disposition Gains on Owned Assets	1.6	32.2		66.5	48.5
Nonoperating Income, Residual Sharing Income	0.8	1.0		3.7	1.7
Nonremarketing Disposition Gain (Loss)	4.9	1.5		10.8	7.0
Portfolio Investments and Capital Additions	314.1	153.9		684.5	663.4
Identifiable assets	9,524.2			9,524.2
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	596.5			596.5		$ 588.4
Assets	9,524.2			$ 9,524.2		9,541.7
Number of business segments | Segment				3
Asset Impairment Charges	(31.5)			$ (31.5)	0.0
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	7.4	58.6		28.6	68.8
Rail North America
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	203.0	204.2		403.7	411.0
Marine operating revenue	0.0	0.0		0.0	0.0
Other Operating Income	18.8	19.2		41.8	37.0
Total Revenues	221.8	223.4		445.5	448.0
Cost of Property Repairs and Maintenance	57.8	61.5		117.7	119.9
Marine operating expense	0.0	0.0		0.0	0.0
Depreciation	64.9	65.2		128.4	130.9
Operating Lease, Expense	9.0	10.2		18.1	21.1
Other operating expense	5.9	8.4		13.2	16.0
Total Expenses	137.6	145.3		277.4	287.9
Gain (Loss) on Disposition of Assets, Net	5.1	33.1		76.7	54.6
Interest expense, net	(34.9)	(32.6)		(69.3)	(69.6)
Other (expense) income	(1.3)	(1.0)		(2.0)	(1.8)
Share of affiliates' earnings (pre-tax)	0.0	0.0		0.0	0.0
Segment profit (loss)	53.1	77.6		173.5	143.3
Disposition Gains on Owned Assets	1.2	31.5		65.6	47.8
Nonoperating Income, Residual Sharing Income	0.1	0.5		2.1	0.6
Nonremarketing Disposition Gain (Loss)	3.8	1.1		9.0	6.2
Portfolio Investments and Capital Additions	253.7	106.4		534.1	215.5
Identifiable assets	6,351.9			6,351.9
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0.3			0.3		0.3
Assets						6,141.7
Asset Impairment Charges	0.0			0.0
Rail International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	66.5	69.0		134.1	135.9
Marine operating revenue	0.0	0.0		0.0	0.0
Other Operating Income	1.9	2.7		4.2	5.2
Total Revenues	68.4	71.7		138.3	141.1
Cost of Property Repairs and Maintenance	12.2	14.2		26.2	29.6
Marine operating expense	0.0	0.0		0.0	0.0
Depreciation	17.2	18.4		35.2	36.7
Operating Lease, Expense	0.0	0.0		0.0	0.0
Other operating expense	2.1	1.7		4.5	3.7
Total Expenses	31.5	34.3		65.9	70.0
Gain (Loss) on Disposition of Assets, Net	1.4	0.8		2.4	1.1
Interest expense, net	(11.1)	(11.1)		(22.3)	(23.3)
Other (expense) income	1.1	0.2		0.7	0.2
Share of affiliates' earnings (pre-tax)	0.0	0.0		0.0	0.0
Segment profit (loss)	28.3	27.3		53.2	49.1
Disposition Gains on Owned Assets	0.3	0.4		0.7	0.4
Nonoperating Income, Residual Sharing Income	0.0	0.0		0.0	0.0
Nonremarketing Disposition Gain (Loss)	1.1	0.4		1.7	0.7
Portfolio Investments and Capital Additions	48.8	40.8		127.7	85.2
Identifiable assets	1,678.4			1,678.4
Assets						1,729.9
Asset Impairment Charges	0.0			0.0
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8.2	8.3		16.5	11.6
Marine operating revenue	5.2	5.1		11.4	8.7
Other Operating Income	0.1	0.2		0.1	0.4
Total Revenues	13.5	13.6		28.0	20.7
Cost of Property Repairs and Maintenance	0.0	0.0		0.0	0.0
Marine operating expense	3.9	5.5		8.1	10.1
Depreciation	4.9	5.0		9.9	7.7
Operating Lease, Expense	0.0	0.0		0.0	0.0
Other operating expense	0.6	0.4		1.1	0.6
Total Expenses	9.4	10.9		19.1	18.4
Gain (Loss) on Disposition of Assets, Net	(30.8)	0.5		(29.9)	1.1
Interest expense, net	(4.6)	(4.4)		(9.3)	(7.5)
Other (expense) income	0.0	0.0		(0.1)	0.0
Share of affiliates' earnings (pre-tax)	15.6	13.4		10.8	22.4
Segment profit (loss)	(15.7)	12.2		(19.6)	18.3
Disposition Gains on Owned Assets	0.0	0.0		0.0	0.0
Nonoperating Income, Residual Sharing Income	0.7	0.5		1.6	1.1
Nonremarketing Disposition Gain (Loss)	0.0	0.0		0.0	0.0
Portfolio Investments and Capital Additions	0.0	0.5		0.0	353.0
Identifiable assets	1,023.7			1,023.7
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	$ 596.2			$ 596.2		588.1
Assets						1,048.7
Number of aircraft engines | AircraftEngines			14
Number of Specialized Gas Vessels | AircraftEngines	5			5
Asset Impairment Charges	$ (31.5)			$ (31.5)
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
Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	7.2	6.1		13.9	9.7
Marine operating revenue	0.0	0.0		0.0	0.0
Other Operating Income	1.8	2.3		3.6	3.4
Total Revenues	9.0	8.4		17.5	13.1
Cost of Property Repairs and Maintenance	0.8	0.9		1.5	1.4
Marine operating expense	0.0	0.0		0.0	0.0
Depreciation	3.0	2.9		6.0	4.8
Operating Lease, Expense	0.0	0.0		0.0	0.0
Other operating expense	0.7	0.9		1.2	1.3
Total Expenses	4.5	4.7		8.7	7.5
Gain (Loss) on Disposition of Assets, Net	0.1	0.3		0.3	0.4
Interest expense, net	(1.3)	(1.9)		(2.2)	(3.2)
Other (expense) income	(11.1)	(7.3)		(11.9)	(7.8)
Share of affiliates' earnings (pre-tax)	0.0	0.0		0.0	0.0
Segment profit (loss)	(7.8)	(5.2)		(5.0)	(5.0)
Disposition Gains on Owned Assets	0.1	0.3		0.2	0.3
Nonoperating Income, Residual Sharing Income	0.0	0.0		0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.0	0.0		0.1	0.1
Portfolio Investments and Capital Additions	11.6	$ 6.2		22.7	$ 9.7
Identifiable assets	470.2			470.2
Assets						$ 621.4
Asset Impairment Charges	$ 0.0			$ 0.0