Sale price for an investment in an affiliate sold during the period

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Number of Business Activities

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Number of Joint Venture Investments

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- Definition

Number of Aircraft Engines

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Number of Aircraft Engines Under Leasing Arrangement

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Operating Leases, Lease Term

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No definition available.

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- Definition

Portfolio proceeds.

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- Definition

Long-Term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership. This does not include advances to clients.

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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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- Definition

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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- Definition

The difference between the carrying value and the sale price of an investment. A gain would be recognized when the sale price of the investment is greater than the carrying value of the investment. This element refers to the Gain included in earnings and not to the cash proceeds of the sale.

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No definition available.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

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No definition available.

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The value of an asset or business acquired in a noncash (or part noncash) acquisition. Noncash is defined as information about all investing and financing activities of an enterprise during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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The cash inflow associated with the amount received from the sale of a business segment or subsidiary or sale of an entity that is related to it but not strictly controlled during the period (for example, an unconsolidated subsidiary, affiliate, joint venture or equity method investment).

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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, $ in Millions	12 Months Ended
	Dec. 31, 2015 EUR (€)	Dec. 31, 2015 USD ($) Business_Activity AircraftEngines Joint_Venture	Dec. 31, 2014 USD ($)	Dec. 31, 2013 EUR (€)	Dec. 31, 2013 USD ($)
Schedule of Equity Method Investments [Line Items]
Noncash or Part Noncash Acquisition, Value of Assets Acquired		$ 0.0	$ 1.1		$ 174.7
Loans to affiliated companies		11.2	16.3
Asset Impairment Charges		33.9	1.3		5.9
Share of affiliates' earnings (net of tax)		45.9	49.5		75.8
Gain on Sale of Investments					2.5
Portfolio proceeds		$ 482.2	264.0		385.3
RRPF Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
GATX ownership percentage in joint venture		50.00%
Number of joint venture investments \| Joint_Venture		15
Number of business activities \| Business_Activity		2
Number of Aircraft Engines \| AircraftEngines		436
Number of Aircraft Engines Under Leasing Arrangement \| AircraftEngines		224
Share of affiliates' earnings (net of tax)		$ 58.4	42.2		$ 46.5
RRPF Joint Ventures [Member] \| Minimum [Member]
Schedule of Equity Method Investments [Line Items]
Lease term	7 years	7 years
RRPF Joint Ventures [Member] \| Maximum [Member]
Schedule of Equity Method Investments [Line Items]
Lease term	10 years	10 years
RRPF Joint Ventures [Member] \| Aircraft Engines [Member]
Schedule of Equity Method Investments [Line Items]
Estimated useful lives of depreciable assets	25 years	25 years
Aae Cargo Ag [Member]
Schedule of Equity Method Investments [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent				37.50%	37.50%
Gain on Sale of Investments					$ 9.3
gmt_SalePrice					114.1
Portfolio proceeds	€ 68.2	$ 77.2		€ 67.5	91.1
Singco/Somagas [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from Divestiture of Businesses and Interests in Affiliates					23.0
Singco/Somagas [Member]
Schedule of Equity Method Investments [Line Items]
Noncash or Part Noncash Acquisition, Value of Assets Acquired					101.3
Aae Cargo Ag [Member]
Schedule of Equity Method Investments [Line Items]
Portfolio proceeds		$ 0.0	$ 0.0		$ 91.1