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Number of Business Activities

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Portfolio proceeds.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of gain (loss) on sale or disposal of property, plant and equipment assets, including oil and gas property and timber property.

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Cash received from sales of long-lived depreciable flight assets, including owned aircraft or capital improvements.

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Investments in Affiliated Companies (Textual) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2022 USD ($) AircraftEngines Business_Activity	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	$ 48.9	$ 2.4	$ 0.3
Share of affiliates' earnings (net of tax)	33.6	1.2	62.2
Portfolio proceeds	$ 269.6	187.1	131.1
RRPF Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
GATX ownership percentage in joint venture	50.00%
Number of business activities \| Business_Activity	2
Number of Aircraft Engines Under Leasing Arrangement \| AircraftEngines	398
Share of affiliates' earnings (net of tax)	$ 33.2	1.2	62.0
Proceeds from Sale of Flight Equipment			233.0
Gain (Loss) on Disposition of Property Plant Equipment			35.3
Number of Aircraft Engines Sold \| AircraftEngines	21
RRPF Joint Ventures [Member] \| Russia
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	$ 11.5
RRPF Joint Ventures [Member] \| Rolls-Royce [Member]
Schedule of Equity Method Investments [Line Items]
Number of Aircraft Engines Under Leasing Arrangement \| AircraftEngines	199
RRPF Joint Ventures [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Lease term				3 years
RRPF Joint Ventures [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Lease term				12 years
RRPF Joint Ventures [Member] \| Aircraft Engines [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Estimated useful lives of depreciable assets	20 years
RRPF Joint Ventures [Member] \| Aircraft Engines [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Estimated useful lives of depreciable assets	25 years
Portfolio Management [Member]
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	$ 34.3	$ 0.0	$ 0.0