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Cover - USD ($)
 12 Months Ended
Dec. 31, 2025
Feb. 25, 2026
Jun. 30, 2025
Cover [Abstract]      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2025    
Current Fiscal Year End Date --12-31    
Document Transition Report false    
Entity File Number 001-38979    
Entity Registrant Name Acadian Asset Management Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 47-1121020    
Entity Address, Address Line One 200 State Street    
Entity Address, City or Town Boston,    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02109    
City Area Code 617    
Local Phone Number 369-7300    
Title of 12(b) Security Common stock, par value $0.001 per share    
Trading Symbol AAMI    
Security Exchange Name NYSE    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
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    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction false    
Entity Shell Company false    
Entity Public Float     $ 935,317,174
Entity Common Stock, Shares Outstanding   35,722,568  
Documents Incorporated by Reference
Portions of the definitive Proxy Statement to be delivered to stockholders in connection with the Annual Meeting of Stockholders to be held on or about June 11, 2026 are incorporated by reference into Part III.
    
Entity Central Index Key 0001748824    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Amendment Flag false