CONSOLIDATED FINANCIAL STATEMENT DETAILS (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Property and equipment
Property and equipment, gross	$ 478,667,000		$ 478,667,000		$ 467,374,000
Less: accumulated depreciation and amortization	(217,549,000)		(217,549,000)		(199,446,000)
Property and equipment, net	261,118,000		261,118,000		267,928,000
Redeemable noncontrolling interests
Balance at the beginning of the period			59,869,000	28,180,000	28,180,000
Purchase of non-controlling interests			(5,652,000)
Noncontrolling interests related to acquisitions					23,583,000
Noncontrolling interest created by a decrease in the ownership of a subsidiary					15,750,000
Contribution from owners of noncontrolling interests			80,000		79,000
Net earnings (loss) attributable to noncontrolling interests			868,000		(5,007,000)
Change in fair value of redeemable noncontrolling interests			1,389,000		(2,059,000)
Change in foreign currency translation adjustment			126,000		(267,000)
Other			(198,000)		(390,000)
Balance at the end of the period	56,482,000		56,482,000		59,869,000
Accumulated other comprehensive income
Foreign currency translation adjustment, net of tax	25,889,000		25,889,000		16,027,000
Unrealized gains on available-for-sale securities, net of tax	36,335,000		36,335,000		1,519,000
Accumulated other comprehensive income, net of tax	62,224,000		62,224,000		17,546,000
Other income (expense), net
Interest income	1,150,000	1,666,000	2,452,000	3,301,000
Interest expense	(1,355,000)	(1,323,000)	(2,710,000)	(2,646,000)
Gain on sales of investments	698,000		1,544,000	3,989,000
Non-income tax refunds related to Match Europe, which was sold in 2009	4,630,000		4,630,000
Other	514,000	(240,000)	473,000	695,000
Other income, net	5,637,000	103,000	6,389,000	5,339,000
Comprehensive income (loss)
Net earnings (loss) attributable to IAC shareholders	42,424,000	13,591,000	60,494,000	(5,114,000)
Change in foreign currency translation adjustment, net	8,934,000	(8,990,000)	9,862,000	(13,663,000)
Change in net unrealized gains (losses) on available-for-sale securities, net of tax	32,447,000	(2,533,000)	34,816,000	(7,742,000)
Other comprehensive income (loss)	41,381,000	(11,523,000)	44,678,000	(21,405,000)
Comprehensive income (loss)	83,805,000	2,068,000	105,172,000	(26,519,000)
Unrealized gains, net of tax, reclassified out of accumulated other comprehensive income into earnings	1,300,000	100,000	1,400,000	2,700,000
Buildings and leasehold improvements
Property and equipment
Property and equipment, gross	234,606,000		234,606,000		234,328,000
Computer equipment and capitalized software
Property and equipment
Property and equipment, gross	191,260,000		191,260,000		183,055,000
Furniture and other equipment
Property and equipment
Property and equipment, gross	41,568,000		41,568,000		41,930,000
Projects in progress
Property and equipment
Property and equipment, gross	6,116,000		6,116,000		2,944,000
Land
Property and equipment
Property and equipment, gross	$ 5,117,000		$ 5,117,000		$ 5,117,000