v3.25.1
Cover - USD ($)
 12 Months Ended
Dec. 31, 2024
Feb. 07, 2025
Jun. 30, 2024
Document Type 10-K    
Amendment Flag false    
Document Annual Report true    
Document Transition Report false    
Document Period End Date Dec. 31, 2024    
Document Fiscal Period Focus FY    
Document Fiscal Year Focus 2024    
Current Fiscal Year End Date --12-31    
Entity File Number 001-39356    
Entity Registrant Name IAC Inc.    
Entity Central Index Key 0001800227    
Entity Tax Identification Number 84-3727412    
Entity Incorporation, State or Country Code DE    
Entity Address, Address Line One 555 West 18th Street    
Entity Address, City or Town New York    
Entity Address, State or Province NY    
Entity Address, Postal Zip Code 10011    
City Area Code 212    
Local Phone Number 314-7300    
Title of 12(b) Security Common Stock, par value $0.0001    
Trading Symbol IAC    
Security Exchange Name NASDAQ    
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    
Entity Shell Company false    
Entity Public Float     $ 3,558,323,640
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Auditor Name Ernst & Young LLP    
Auditor Location New York, NY    
Auditor Firm ID 42    
Common Class A [Member]      
Entity Common Stock, Shares Outstanding   77,493,837  
Common Class B [Member]      
Entity Common Stock, Shares Outstanding   5,789,499