GOODWILL AND INTANGIBLE ASSETS (Details2) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	$ 1,358,524,000
Additions	212,289,000
(Deductions)	(3,381,000)
Foreign Exchange Translation	(10,599,000)
Balance at the end of the period	1,556,833,000
Search and Applications
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	526,444,000
Additions	182,969,000
(Deductions)	(218,000)
Balance at the end of the period	709,195,000
IAC Search & Media
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	526,444,000
Additions	182,969,000
(Deductions)	(218,000)
Balance at the end of the period	709,195,000
Goodwill accumulated impairment losses	916,900,000	916,900,000
Match
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	667,073,000
Additions	13,347,000
(Deductions)	(3,163,000)
Foreign Exchange Translation	(10,216,000)
Balance at the end of the period	667,041,000
Local
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	127,698,000
Additions	15,973,000
Foreign Exchange Translation	(383,000)
Balance at the end of the period	143,288,000
HomeAdvisor
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	109,947,000
Additions	1,880,000
Foreign Exchange Translation	(383,000)
Balance at the end of the period	111,444,000
CityGrid Media
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period	17,751,000
Additions	14,093,000
Balance at the end of the period	31,844,000
Media
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period		15,590,000
Balance at the end of the period	15,590,000	15,590,000
Connected Ventures
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period		8,267,000
Balance at the end of the period	8,267,000	8,267,000
Goodwill accumulated impairment losses	11,600,000	11,600,000
DailyBurn
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period		7,323,000
Balance at the end of the period	7,323,000	7,323,000
Other
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period		21,719,000
Balance at the end of the period	21,719,000	21,719,000
Shoebuy
Balance of goodwill by reporting unit, including the changes in the carrying value of goodwill
Balance at the beginning of the period		21,719,000
Balance at the end of the period	21,719,000	21,719,000
Goodwill accumulated impairment losses	$ 28,000,000	$ 28,000,000