v3.25.1
Document and Entity Information
 3 Months Ended
Mar. 31, 2025
shares
Document Information [Line Items]  
Document Transition Report false
Entity Registrant Name GATX Corporation
Document Period End Date Mar. 31, 2025
City Area Code 312
Local Phone Number 621-6200
Title of 12(b) Security Common Stock
Entity Current Reporting Status Yes
Entity Interactive Data Current Yes
Entity Filer Category Large Accelerated Filer
Entity Small Business false
Entity Emerging Growth Company false
Entity Common Stock, Shares Outstanding 35,700,000
Entity Shell Company false
Entity Address, Address Line One 233 South Wacker Drive
Entity Address, City or Town Chicago
Entity Address, State or Province IL
Entity Address, Postal Zip Code 60606
Amendment Flag false
Entity Central Index Key 0000040211
Document Fiscal Year Focus 2025
Document Fiscal Period Focus Q1
Current Fiscal Year End Date --12-31
Document Quarterly Report true
Entity Incorporation, State or Country Code NY
Entity Tax Identification Number 36-1124040
Document Type 10-Q
Entity File Number 1-2328
NEW YORK STOCK EXCHANGE, INC. [Member]  
Document Information [Line Items]  
Trading Symbol GATX
Security Exchange Name NYSE
CHICAGO STOCK EXCHANGE, INC [Member]  
Document Information [Line Items]  
Trading Symbol GATX
Security Exchange Name CHX