v3.26.1
Cover - USD ($)
 12 Months Ended
Dec. 31, 2025
Feb. 02, 2026
Jun. 30, 2025
Document Information [Line Items]      
Document Type 10-K/A    
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 001-39356    
Entity Registrant Name IAC Inc.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 84-3727412    
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    
ICFR Auditor Attestation Flag true    
Document Financial Statement Error Correction [Flag] false    
Entity Shell Company false    
Entity Public Float     $ 2,712,201,206
Entity Central Index Key 0001800227    
Document Fiscal Year Focus 2025    
Document Fiscal Period Focus FY    
Auditor Name Ernst & Young LLP    
Auditor Location New York, NY    
Auditor Firm ID 42    
Amendment Flag true    
Amendment Description EXPLANATORY NOTEIAC Inc. (“IAC” or the “Registrant”) is filing this Amendment No. 1 on Form 10-K/A (“Amendment No. 1”) to its Annual Report on Form 10-K for the fiscal year ended December 31, 2025, which was filed with the U.S. Securities and Exchange Commission (the “SEC”) on February 20, 2026 (the “Original Form 10-K”). This Amendment No. 1 on Form 10-K/A is being filed for the sole purpose of amending Part III of the Original Form 10-K to include the information required by Part III (Items 10, 11, 12, 13 and 14) of Form 10-K. This information was previously omitted from the Original Form 10-K in reliance on General Instruction G(3) to Form 10-K, which permits the information required by Part III to be incorporated by reference from the Registrant’s definitive proxy statement if such statement is filed no later than 120 days after the end of its fiscal year.In addition, pursuant to applicable SEC rules, Item 15 of Part IV has been amended to include contemporaneously dated certifications of the Registrant’s principal executive officer and principal financial officer pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 (the “302 Certifications”), which are filed as Exhibits 31.4 and 31.5 hereto. Because this Amendment No. 1 on Form 10-K/A does not contain any financial statements or other financial information, nor does it contain or amend any disclosure with respect to Items 307 and 308 of Regulation S-K of the Securities Act of 1933, as amended: (i) paragraphs 3, 4 and 5 of the 302 Certifications have been omitted and (ii) no certifications pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 are being filed as exhibits hereto.Except as described above, no other changes have been made to the Original Form 10-K. The Original Form 10-K continues to speak as of the date on which it was filed, and the Registrant has not updated the disclosures contained therein to reflect any events that have occurred at a date subsequent to the date on which it was filed. Accordingly, this Amendment No. 1 on Form 10-K/A should be read in conjunction with the Original Form 10-K and with the Registrant’s other filings made with the SEC subsequent to the filing of the Original Form 10-K.    
Class A Common Stock      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   71,118,465  
Class B Common Stock      
Document Information [Line Items]      
Entity Common Stock, Shares Outstanding   5,789,499