Financial Data of Business Segments (Details) $ in Millions	3 Months Ended				9 Months Ended
	Sep. 30, 2022 USD ($)	Jun. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Mar. 31, 2021 USD ($) AircraftEngines	Sep. 30, 2022 USD ($) Segment	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net income	$ 29.1		$ 40.1		$ 107.5	$ 82.1
Provision for Income Taxes, Equity Method Investment	2.5		1.0		6.0	47.8
Lease Income	292.4		283.9		860.6	852.1
Marine operating revenue	4.8		5.0		16.2	13.7
Other Operating Income	23.8		24.6		73.5	70.6
Total Revenues	321.0		313.5		950.3	936.4
Cost of Property Repairs and Maintenance	75.9		74.2		221.3	225.1
Marine operating expense	3.6		3.7		11.7	13.8
Depreciation	88.7		91.1		268.2	271.2
Operating Lease, Expense	9.0		9.0		27.1	30.1
Other operating expense	8.7		9.7		28.7	31.3
Total Expenses	185.9		187.7		557.0	571.5
Gain (Loss) on Disposition of Assets, Net	3.9		21.9		53.4	79.1
Interest expense, net	(53.6)		(49.8)		(156.7)	(153.4)
Other (expense) income	(2.5)		(0.3)		(15.8)	(9.7)
Share of affiliates' earnings (pre-tax)	10.0		3.8		20.8	26.2
Segment profit (loss)	92.9		101.4		295.0	307.1
Income tax benefit	13.7		14.4		38.8	36.4
Selling, general and administrative	47.6		45.9		142.7	140.8
Disposition Gains on Owned Assets	9.1		14.9		75.6	63.4
Nonoperating Income, Residual Sharing Income	1.0		0.8		4.7	2.5
Nonremarketing Disposition Gain (Loss)	4.6		6.2		15.4	13.2
Portfolio Investments and Capital Additions	203.4		229.8		887.9	893.2
Identifiable assets	9,875.4				9,875.4
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(604.3)				(604.3)		$ (588.4)
Assets	(9,875.4)				$ (9,875.4)		(9,541.7)
Number of business segments | Segment					3
Asset impairments	10.8				$ 42.3	0.0
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	16.2		15.4		44.8	84.2
Rail North America
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	211.3		200.4		615.0	611.4
Marine operating revenue	0.0		0.0		0.0	0.0
Other Operating Income	20.0		19.4		61.8	56.4
Total Revenues	231.3		219.8		676.8	667.8
Cost of Property Repairs and Maintenance	62.4		58.9		180.1	178.8
Marine operating expense	0.0		0.0		0.0	0.0
Depreciation	65.3		64.8		193.7	195.7
Operating Lease, Expense	9.0		9.0		27.1	30.1
Other operating expense	6.0		6.6		19.2	22.6
Total Expenses	142.7		139.3		420.1	427.2
Gain (Loss) on Disposition of Assets, Net	13.3		20.2		90.0	74.8
Interest expense, net	(36.5)		(32.9)		(105.8)	(102.5)
Other (expense) income	(1.4)		(1.1)		(3.4)	(2.9)
Share of affiliates' earnings (pre-tax)	0.3		(0.2)		0.3	(0.2)
Segment profit (loss)	64.3		66.5		237.8	209.8
Disposition Gains on Owned Assets	8.8		14.4		74.4	62.2
Nonoperating Income, Residual Sharing Income	0.2		0.2		2.3	0.8
Nonremarketing Disposition Gain (Loss)	4.3		5.6		13.3	11.8
Portfolio Investments and Capital Additions	142.5		178.9		676.6	394.4
Identifiable assets	6,412.3				6,412.3
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(0.6)				(0.6)		0.3
Assets							6,141.7
Asset impairments	0.0				0.0
Rail International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	65.3		68.8		199.4	204.7
Marine operating revenue	0.0		0.0		0.0	0.0
Other Operating Income	2.3		2.7		6.5	7.9
Total Revenues	67.6		71.5		205.9	212.6
Cost of Property Repairs and Maintenance	12.8		14.0		39.0	43.6
Marine operating expense	0.0		0.0		0.0	0.0
Depreciation	16.8		18.5		52.0	55.2
Operating Lease, Expense	0.0		0.0		0.0	0.0
Other operating expense	1.5		1.8		6.0	5.5
Total Expenses	31.1		34.3		97.0	104.3
Gain (Loss) on Disposition of Assets, Net	(10.3)		0.9		(7.9)	2.0
Interest expense, net	(11.2)		(10.9)		(33.5)	(34.2)
Other (expense) income	(0.5)		(0.2)		0.2	0.0
Share of affiliates' earnings (pre-tax)	0.0		0.0		0.0	0.0
Segment profit (loss)	14.5		27.0		67.7	76.1
Disposition Gains on Owned Assets	0.3		0.3		1.0	0.7
Nonoperating Income, Residual Sharing Income	0.0		0.0		0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.2		0.6		1.9	1.3
Portfolio Investments and Capital Additions	50.1		40.9		177.8	126.1
Identifiable assets	1,610.2				1,610.2
Assets							(1,729.9)
Asset impairments	(10.8)				10.8
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8.3		8.2		24.8	19.8
Marine operating revenue	4.8		5.0		16.2	13.7
Other Operating Income	0.0		0.1		0.1	0.5
Total Revenues	13.1		13.3		41.1	34.0
Cost of Property Repairs and Maintenance	0.0		0.0		0.0	0.0
Marine operating expense	3.6		3.7		11.7	13.8
Depreciation	3.7		4.9		13.6	12.6
Operating Lease, Expense	0.0		0.0		0.0	0.0
Other operating expense	0.6		0.6		1.7	1.2
Total Expenses	7.9		9.2		27.0	27.6
Gain (Loss) on Disposition of Assets, Net	0.8		0.6		(29.1)	1.7
Interest expense, net	(4.6)		(4.5)		(13.9)	(12.0)
Other (expense) income	0.1		2.0		0.0	2.0
Share of affiliates' earnings (pre-tax)	9.7		4.0		20.5	26.4
Segment profit (loss)	11.2		6.2		(8.4)	24.5
Disposition Gains on Owned Assets	0.0		0.0		0.0	0.0
Nonoperating Income, Residual Sharing Income	0.8		0.6		2.4	1.7
Nonremarketing Disposition Gain (Loss)	0.0		0.0		0.0	0.0
Portfolio Investments and Capital Additions	0.0		0.0		0.0	353.0
Identifiable assets	991.1				991.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(603.7)				(603.7)		588.1
Assets							1,048.7
Number of aircraft engines | AircraftEngines				14
Asset impairments	0.0	$ 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	7.5		6.5		21.4	16.2
Marine operating revenue	0.0		0.0		0.0	0.0
Other Operating Income	1.5		2.4		5.1	5.8
Total Revenues	9.0		8.9		26.5	22.0
Cost of Property Repairs and Maintenance	0.7		1.3		2.2	2.7
Marine operating expense	0.0		0.0		0.0	0.0
Depreciation	2.9		2.9		8.9	7.7
Operating Lease, Expense	0.0		0.0		0.0	0.0
Other operating expense	0.6		0.7		1.8	2.0
Total Expenses	4.2		4.9		12.9	12.4
Gain (Loss) on Disposition of Assets, Net	0.1		0.2		0.4	0.6
Interest expense, net	(1.3)		(1.5)		(3.5)	(4.7)
Other (expense) income	(0.7)		(1.0)		(12.6)	(8.8)
Share of affiliates' earnings (pre-tax)	0.0		0.0		0.0	0.0
Segment profit (loss)	2.9		1.7		(2.1)	(3.3)
Disposition Gains on Owned Assets	0.0		0.2		0.2	0.5
Nonoperating Income, Residual Sharing Income	0.0		0.0		0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.1		0.0		0.2	0.1
Portfolio Investments and Capital Additions	10.8		$ 10.0		33.5	$ 19.7
Identifiable assets	861.8				861.8
Assets							$ (621.4)
Asset impairments	$ 0.0				$ 0.0