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Number of Aircraft Engines Under Leasing Arrangement

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Operating Leases, Lease Term

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Portfolio proceeds.

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Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

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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 income (loss) for proportionate share of equity method investee's income (loss).

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Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Investments in Affiliated Companies (Textual) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) AircraftEngines Business_Activity	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Asset Impairment Charges	$ 0.3	$ 6.6	$ 9.0
Share of affiliates' earnings (net of tax)	62.2	76.5	50.3
Portfolio proceeds	$ 131.1	250.3	234.4
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	215
Share of affiliates' earnings (net of tax)	$ 62.0	$ 76.5	49.8
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	18 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	$ 0.0	$ 6.2	$ 4.5