v3.26.1
Document and Entity Information - USD ($)
 12 Months Ended
Dec. 31, 2025
Mar. 18, 2026
Jun. 30, 2025
Document and Entity Information      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Document Transition Report false    
Entity File Number 001-42629    
Entity Registrant Name CARTESIAN GROWTH CORPORATION III    
Entity Incorporation, State or Country Code E9    
Entity Tax Identification Number 00-0000000    
Entity Address, Address Line One 505 Fifth Avenue    
Entity Address, Address Line Two 15th Floor    
Entity Address, City or Town New York    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10017    
City Area Code 212    
Local Phone Number 461-6363    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company true    
Entity Ex Transition Period false    
ICFR Auditor Attestation Flag false    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company true    
Entity Public Float     $ 277,656,000
Entity Central Index Key 0002049662    
Current Fiscal Year End Date --12-31    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false    
Auditor Name CBIZ CPAs P.C.    
Auditor Location Houston, TX    
Auditor Firm ID 199    
Unit      
Document and Entity Information      
Title of 12(b) Security Units, each consisting of one Class A Ordinary Share and one-half of one redeemable warrant    
Trading Symbol CGCTU    
Security Exchange Name NASDAQ    
Class A ordinary shares      
Document and Entity Information      
Title of 12(b) Security Class A Ordinary Shares, par value $0.0001 per share    
Trading Symbol CGCT    
Security Exchange Name NASDAQ    
Entity Common Stock, Shares Outstanding   27,600,000  
Warrant      
Document and Entity Information      
Title of 12(b) Security Warrants, each whole warrant exercisable for one Class A Ordinary Share, at an exercise price of $11.50    
Trading Symbol CGCTW    
Security Exchange Name NASDAQ    
Class B ordinary shares      
Document and Entity Information      
Entity Common Stock, Shares Outstanding   6,900,000