Financial Data of Business Segments (Details) $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2023 USD ($) AircraftEngines	Mar. 31, 2023 USD ($) AircraftEngines	Sep. 30, 2022 AircraftEngines	Jun. 30, 2022 USD ($) AircraftEngines	Jun. 30, 2023 USD ($) AircraftEngines Segment	Jun. 30, 2022 USD ($) AircraftEngines	Dec. 31, 2022 USD ($)
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Net Income (Loss) Attributable to Parent	$ 63.3			$ 2.6	$ 140.7	$ 78.4
Provision for Income Taxes, Equity Method Investment	6.3			4.7	13.2	3.5
Lease Income	308.6			284.9	610.6	568.2
Marine operating revenue	2.0			5.2	5.5	11.4
Other Operating Income	32.6			22.6	66.0	49.7
Total Revenues	343.2			312.7	682.1	629.3
Cost of Property Repairs and Maintenance	82.3			70.8	166.2	145.4
Marine operating expense	2.4			3.9	4.4	8.1
Depreciation	92.1			90.0	181.9	179.5
Operating Lease, Expense	9.0			9.0	18.0	18.1
Other operating expense	11.0			9.3	22.0	20.0
Total Expenses	196.8			183.0	392.5	371.1
Gain (Loss) on Disposition of Assets, Net	41.1			(24.2)	88.2	49.5
Interest expense, net	(63.7)			(51.9)	(122.7)	(103.1)
Other (expense) income	(4.9)			(11.3)	(8.9)	(13.3)
Share of affiliates' earnings (pre-tax)	20.3			15.6	47.9	10.8
Segment profit (loss)	139.2			57.9	294.1	202.1
Income tax benefit	17.6			2.7	37.8	25.1
Selling, general and administrative	52.0			47.9	102.4	95.1
Disposition Gains on Owned Assets	36.9			1.6	81.6	66.5
Nonoperating Income, Residual Sharing Income	0.2			0.8	0.4	3.7
Nonremarketing Disposition Gain (Loss)	4.0			4.9	7.4	10.8
Portfolio Investments and Capital Additions	486.6			314.1	873.6	684.5
Identifiable assets	10,590.1				10,590.1
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(611.7)				(611.7)		$ (575.1)
Assets	(10,590.1)				$ (10,590.1)		(10,072.0)
Number of business segments | Segment					3
Asset Impairment Charges	$ 0.0			$ 31.5	$ 1.2	$ 31.5
Number of Specialized Gas Vessels | AircraftEngines	1	2		5	1	5
Number of Specialized Gas Vessels Sold | AircraftEngines	1	1
Number of Aircraft Engines Acquired | AircraftEngines	9
Segment Reporting Information [Line Items]
Lease Income	$ 308.6			$ 284.9	$ 610.6	$ 568.2
Marine operating revenue	2.0			5.2	5.5	11.4
Other Operating Income	32.6			22.6	66.0	49.7
Total Revenues	343.2			312.7	682.1	629.3
Cost of Property Repairs and Maintenance	82.3			70.8	166.2	145.4
Marine operating expense	2.4			3.9	4.4	8.1
Depreciation	92.1			90.0	181.9	179.5
Operating Lease, Expense	9.0			9.0	18.0	18.1
Other operating expense	11.0			9.3	22.0	20.0
Operating Costs and Expenses	196.8			183.0	392.5	371.1
Gain (Loss) on Disposition of Assets, Net	41.1			(24.2)	88.2	49.5
Interest Expense	63.7			51.9	122.7	103.1
Other (expense) income	(4.9)			(11.3)	(8.9)	(13.3)
Share of affiliates' earnings (pre-tax)	20.3			15.6	47.9	10.8
Segment Profit Loss	139.2			57.9	294.1	202.1
Portfolio Investments and Capital Additions	486.6			314.1	873.6	684.5
Net Income (Loss) Attributable to Parent	63.3			2.6	140.7	78.4
Disposition Gains on Owned Assets	36.9			1.6	81.6	66.5
Nonoperating Income, Residual Sharing Income	0.2			0.8	0.4	3.7
Nonremarketing Disposition Gain (Loss)	4.0			4.9	7.4	10.8
Asset Impairment Charges	0.0			31.5	1.2	31.5
Parent [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income tax benefit	23.9			7.4	51.0	28.6
Rail North America
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	218.9			203.0	434.0	403.7
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	21.5			18.8	45.3	41.8
Total Revenues	240.4			221.8	479.3	445.5
Cost of Property Repairs and Maintenance	66.8			57.8	133.7	117.7
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	66.1			64.9	131.6	128.4
Operating Lease, Expense	9.0			9.0	18.0	18.1
Other operating expense	6.7			5.9	13.7	13.2
Total Expenses	148.6			137.6	297.0	277.4
Gain (Loss) on Disposition of Assets, Net	34.1			5.1	81.9	76.7
Interest expense, net	(44.5)			(34.9)	(86.8)	(69.3)
Other (expense) income	(2.1)			(1.3)	(2.5)	(2.0)
Share of affiliates' earnings (pre-tax)	0.0			0.0	(0.4)	0.0
Segment profit (loss)	79.3			53.1	174.5	173.5
Disposition Gains on Owned Assets	30.7			1.2	75.4	65.6
Nonoperating Income, Residual Sharing Income	0.1			0.1	0.2	2.1
Nonremarketing Disposition Gain (Loss)	3.3			3.8	6.3	9.0
Portfolio Investments and Capital Additions	161.3			253.7	457.8	534.1
Identifiable assets	6,680.2				6,680.2		6,445.7
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(0.4)				(0.4)		0.8
Asset Impairment Charges					0.0
Segment Reporting Information [Line Items]
Lease Income	218.9			203.0	434.0	403.7
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	21.5			18.8	45.3	41.8
Total Revenues	240.4			221.8	479.3	445.5
Cost of Property Repairs and Maintenance	66.8			57.8	133.7	117.7
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	66.1			64.9	131.6	128.4
Operating Lease, Expense	9.0			9.0	18.0	18.1
Other operating expense	6.7			5.9	13.7	13.2
Operating Costs and Expenses	148.6			137.6	297.0	277.4
Gain (Loss) on Disposition of Assets, Net	34.1			5.1	81.9	76.7
Interest Expense	44.5			34.9	86.8	69.3
Other (expense) income	(2.1)			(1.3)	(2.5)	(2.0)
Share of affiliates' earnings (pre-tax)	0.0			0.0	(0.4)	0.0
Segment Profit Loss	79.3			53.1	174.5	173.5
Portfolio Investments and Capital Additions	161.3			253.7	457.8	534.1
Disposition Gains on Owned Assets	30.7			1.2	75.4	65.6
Nonoperating Income, Residual Sharing Income	0.1			0.1	0.2	2.1
Nonremarketing Disposition Gain (Loss)	3.3			3.8	6.3	9.0
Asset Impairment Charges					0.0
Rail International
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	73.1			66.5	143.5	134.1
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	3.1			1.9	6.0	4.2
Total Revenues	76.2			68.4	149.5	138.3
Cost of Property Repairs and Maintenance	14.6			12.2	30.5	26.2
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	16.6			17.2	32.3	35.2
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	2.3			2.1	4.5	4.5
Total Expenses	33.5			31.5	67.3	65.9
Gain (Loss) on Disposition of Assets, Net	0.7			1.4	1.5	2.4
Interest expense, net	(13.5)			(11.1)	(26.0)	(22.3)
Other (expense) income	(2.6)			1.1	(6.9)	0.7
Share of affiliates' earnings (pre-tax)	0.0			0.0	0.0	0.0
Segment profit (loss)	27.3			28.3	50.8	53.2
Disposition Gains on Owned Assets	0.1			0.3	0.5	0.7
Nonoperating Income, Residual Sharing Income	0.0			0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.6			1.1	1.0	1.7
Portfolio Investments and Capital Additions	77.3			48.8	158.4	127.7
Identifiable assets	1,952.3				1,952.3		1,774.4
Asset Impairment Charges					0.0		14.6
Segment Reporting Information [Line Items]
Lease Income	73.1			66.5	143.5	134.1
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	3.1			1.9	6.0	4.2
Total Revenues	76.2			68.4	149.5	138.3
Cost of Property Repairs and Maintenance	14.6			12.2	30.5	26.2
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	16.6			17.2	32.3	35.2
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	2.3			2.1	4.5	4.5
Operating Costs and Expenses	33.5			31.5	67.3	65.9
Gain (Loss) on Disposition of Assets, Net	0.7			1.4	1.5	2.4
Interest Expense	13.5			11.1	26.0	22.3
Other (expense) income	(2.6)			1.1	(6.9)	0.7
Share of affiliates' earnings (pre-tax)	0.0			0.0	0.0	0.0
Segment Profit Loss	27.3			28.3	50.8	53.2
Portfolio Investments and Capital Additions	77.3			48.8	158.4	127.7
Disposition Gains on Owned Assets	0.1			0.3	0.5	0.7
Nonoperating Income, Residual Sharing Income	0.0			0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.6			1.1	1.0	1.7
Asset Impairment Charges					0.0		14.6
Portfolio Management
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8.1			8.2	16.4	16.5
Marine operating revenue	2.0			5.2	5.5	11.4
Other Operating Income	6.4			0.1	10.9	0.1
Total Revenues	16.5			13.5	32.8	28.0
Cost of Property Repairs and Maintenance	0.0			0.0	0.0	0.0
Marine operating expense	2.4			3.9	4.4	8.1
Depreciation	6.1			4.9	11.5	9.9
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	1.4			0.6	2.3	1.1
Total Expenses	9.9			9.4	18.2	19.1
Gain (Loss) on Disposition of Assets, Net	6.0			(30.8)	4.5	(29.9)
Interest expense, net	(6.5)			(4.6)	(12.2)	(9.3)
Other (expense) income	0.2			0.0	(0.3)	(0.1)
Share of affiliates' earnings (pre-tax)	20.3			15.6	48.3	10.8
Segment profit (loss)	26.6			(15.7)	54.9	(19.6)
Disposition Gains on Owned Assets	5.9			0.0	5.5	0.0
Nonoperating Income, Residual Sharing Income	0.1			0.7	0.2	1.6
Nonremarketing Disposition Gain (Loss)	0.0			0.0	0.0	0.0
Portfolio Investments and Capital Additions	239.0			0.0	239.0	0.0
Identifiable assets	1,371.6				1,371.6		1,106.6
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(611.3)				(611.3)		574.3
Asset Impairment Charges	$ 0.0	$ 1.2		31.5	1.2	31.5	34.3
Number of Specialized Gas Vessels Sold | AircraftEngines		1	2
Number of Aircraft Engines Acquired | AircraftEngines	9
Segment Reporting Information [Line Items]
Lease Income	$ 8.1			8.2	16.4	16.5
Marine operating revenue	2.0			5.2	5.5	11.4
Other Operating Income	6.4			0.1	10.9	0.1
Total Revenues	16.5			13.5	32.8	28.0
Cost of Property Repairs and Maintenance	0.0			0.0	0.0	0.0
Marine operating expense	2.4			3.9	4.4	8.1
Depreciation	6.1			4.9	11.5	9.9
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	1.4			0.6	2.3	1.1
Operating Costs and Expenses	9.9			9.4	18.2	19.1
Gain (Loss) on Disposition of Assets, Net	6.0			(30.8)	4.5	(29.9)
Interest Expense	6.5			4.6	12.2	9.3
Other (expense) income	0.2			0.0	(0.3)	(0.1)
Share of affiliates' earnings (pre-tax)	20.3			15.6	48.3	10.8
Segment Profit Loss	26.6			(15.7)	54.9	(19.6)
Portfolio Investments and Capital Additions	239.0			0.0	239.0	0.0
Disposition Gains on Owned Assets	5.9			0.0	5.5	0.0
Nonoperating Income, Residual Sharing Income	0.1			0.7	0.2	1.6
Nonremarketing Disposition Gain (Loss)	0.0			0.0	0.0	0.0
Asset Impairment Charges	0.0	$ 1.2		31.5	1.2	31.5	34.3
Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Lease Income	8.5			7.2	16.7	13.9
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	1.6			1.8	3.8	3.6
Total Revenues	10.1			9.0	20.5	17.5
Cost of Property Repairs and Maintenance	0.9			0.8	2.0	1.5
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	3.3			3.0	6.5	6.0
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	0.6			0.7	1.5	1.2
Total Expenses	4.8			4.5	10.0	8.7
Gain (Loss) on Disposition of Assets, Net	0.3			0.1	0.3	0.3
Interest expense, net	0.8			(1.3)	2.3	(2.2)
Other (expense) income	(0.4)			(11.1)	0.8	(11.9)
Share of affiliates' earnings (pre-tax)	0.0			0.0	0.0	0.0
Segment profit (loss)	6.0			(7.8)	13.9	(5.0)
Disposition Gains on Owned Assets	0.2			0.1	0.2	0.2
Nonoperating Income, Residual Sharing Income	0.0			0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)	0.1			0.0	0.1	0.1
Portfolio Investments and Capital Additions	9.0			11.6	18.4	22.7
Identifiable assets	586.0				586.0		$ 745.3
Segment Reporting Information [Line Items]
Lease Income	8.5			7.2	16.7	13.9
Marine operating revenue	0.0			0.0	0.0	0.0
Other Operating Income	1.6			1.8	3.8	3.6
Total Revenues	10.1			9.0	20.5	17.5
Cost of Property Repairs and Maintenance	0.9			0.8	2.0	1.5
Marine operating expense	0.0			0.0	0.0	0.0
Depreciation	3.3			3.0	6.5	6.0
Operating Lease, Expense	0.0			0.0	0.0	0.0
Other operating expense	0.6			0.7	1.5	1.2
Operating Costs and Expenses	4.8			4.5	10.0	8.7
Gain (Loss) on Disposition of Assets, Net	0.3			0.1	0.3	0.3
Interest Expense	(0.8)			1.3	(2.3)	2.2
Other (expense) income	(0.4)			(11.1)	0.8	(11.9)
Share of affiliates' earnings (pre-tax)	0.0			0.0	0.0	0.0
Segment Profit Loss	6.0			(7.8)	13.9	(5.0)
Portfolio Investments and Capital Additions	9.0			11.6	18.4	22.7
Disposition Gains on Owned Assets	0.2			0.1	0.2	0.2
Nonoperating Income, Residual Sharing Income	0.0			0.0	0.0	0.0
Nonremarketing Disposition Gain (Loss)	$ 0.1			$ 0.0	$ 0.1	$ 0.1