Cover - USD ($)	12 Months Ended
	Dec. 31, 2019	Jan. 31, 2020	Jun. 30, 2019
Document Information [Line Items]
Document Type	10-K/A
Amendment Flag	true
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2019
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Current Fiscal Year End Date	--12-31
Entity File Number	000-20570
Entity Registrant Name	IAC/INTERACTIVECORP
Entity Central Index Key	0000891103
Entity Tax Identification Number	59-2712887
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 $0.001
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			$ 16,892,708,488
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		78,970,141
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		5,789,499