v3.25.3

Legal Proceedings and Other Contingencies Legal Proceedings and Other Contingencies (Details) - Almasy, et al. v. Norfolk Southern Corp $ in Millions		9 Months Ended
	Feb. 03, 2025 plaintiff defendant	Sep. 30, 2025 USD ($) individual_resident
Other Commitments [Line Items]
Number of individual residents \| individual_resident		40
Litigation Settlement, Amount Awarded to Other Party \| $		$ 600.0
Loss Contingency, Number of Plaintiffs	750
Loss Contingency, Number Of Plaintiffs Opted Out Of Prior Settlement Agreements	184
Loss Contingency, Number of Defendants \| defendant	60
Loss Contingency, Number Of Plaintiffs Opted Into Prior Settlement Agreements	550

Loss Contingency, Number Of Plaintiffs Opted Into Prior Settlement Agreements

+ References

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Namespace Prefix:	gmt_
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- Definition

Loss Contingency, Number Of Plaintiffs Opted Out Of Prior Settlement Agreements

+ References

No definition available.

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- Definition

Number of individual residents

+ References

No definition available.

+ Details

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Namespace Prefix:	gmt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of defendants named in a legal action.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483076/450-20-50-9

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Number of plaintiffs that have filed claims pertaining to a loss contingency.

+ References

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

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Period Type:

GATX CORP 10-Q