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Description of Business (Details) $ in Millions	3 Months Ended				9 Months Ended		12 Months Ended
Description of Business (Details) $ in Millions	Sep. 30, 2023 USD ($) AircraftEngines	Jun. 30, 2023 USD ($) AircraftEngines	Mar. 31, 2023 USD ($) AircraftEngines	Sep. 30, 2022 USD ($) AircraftEngines	Sep. 30, 2023 USD ($) AircraftEngines Segment	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)	Jun. 30, 2022 AircraftEngines
Schedule of Equity Method Investments [Line Items]
Number of business segments \| Segment					3
Net gain on asset dispositions \| $	$ 16.9			$ 3.9	$ 105.1	$ 53.4
Number of Specialized Gas Vessels Sold		1	1
Asset Impairment Charges \| $	0.0			10.8	1.2	42.3
Portfolio Investments and Capital Additions \| $	$ 363.9			$ 203.4	1,237.5	887.9
Number of Aircraft Engines Acquired	1	9
Number of Specialized Gas Vessels								5
Number of Specialized Gas Vessels								5
Portfolio Management
Schedule of Equity Method Investments [Line Items]
Number of Specialized Gas Vessels Sold		1	1	2
Asset Impairment Charges \| $			$ 1.2	$ 0.0	1.2	31.5	$ 34.3
Portfolio Investments and Capital Additions \| $	$ 28.3	$ 239.0		0.0	$ 267.3	0.0
Number of Aircraft Engines Acquired					10
Number of Specialized Gas Vessels	1		2		1
Number of Specialized Gas Vessels	1		2		1
Rail International
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges \| $				10.8	$ 0.0	10.8	$ 14.6
Portfolio Investments and Capital Additions \| $	$ 129.6			$ 50.1	$ 288.0	$ 177.8