GOODWILL AND INTANGIBLE ASSETS (Details) (USD $)	12 Months Ended			12 Months Ended							12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Dec. 31, 2011 Maximum	Dec. 31, 2010 Maximum	Dec. 31, 2011 Minimum	Dec. 31, 2010 Minimum	Dec. 31, 2010 Media & Other	Dec. 31, 2011 Media & Other	Dec. 31, 2009 Media & Other	Dec. 31, 2010 Shoebuy	Dec. 31, 2011 Shoebuy	Dec. 31, 2009 Shoebuy	Dec. 31, 2009 Search	Dec. 31, 2011 Search	Dec. 31, 2010 Search	Dec. 31, 2010 IAC Search & Media	Dec. 31, 2009 IAC Search & Media	Dec. 31, 2011 IAC Search & Media
Goodwill and intangible assets
Impairment charges on goodwill	$ 28,032,000	$ 916,868,000						$ 28,032,000			$ 28,032,000			$ 916,868,000				$ 916,900,000
Impairment charges on indefinite-lived intangible assets											4,500,000						11,000,000	104,100,000
Impairment charges on finite-lived intangible assets																		24,200,000
Discount rates used for impairment assessment of goodwill (as a percent)				20.00%	20.00%	13.00%	13.00%
Discount rates used for impairment assessment of indefinite-lived intangible assets (as a percent)				20.00%	20.00%	13.00%	13.00%
Royalty rates used for impairment assessment of indefinite-lived intangible assets (as a percent)				9.00%	10.00%	1.00%	1.00%
Balance of goodwill and intangible assets, net
Goodwill	989,493,000	967,735,000	1,358,524,000					30,148,000	29,986,000	58,180,000	21,712,000	21,719,000	49,744,000	545,054,000	551,518,000	551,454,000	534,004,000	527,604,000	533,767,000
Intangible assets with indefinite lives	237,021,000		351,488,000					13,580,000	12,980,000						168,986,000	168,500,000
Intangible assets with definite lives, net	8,023,000		26,619,000					1,872,000	3,825,000						500,000	1,941,000
Total goodwill and intangible assets, net	$ 1,234,537,000		$ 1,736,631,000