CONSOLIDATED FINANCIAL STATEMENT DETAILS (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Property and equipment, net
Property and equipment, gross	$ 487,003,000		$ 487,003,000		$ 467,374,000
Less: accumulated depreciation and amortization	(227,000,000)		(227,000,000)		(199,446,000)
Property and equipment, net	260,003,000		260,003,000		267,928,000
Redeemable noncontrolling interests
Balance at the beginning of the period			59,869,000	28,180,000	28,180,000
Purchase of noncontrolling interests			(5,779,000)
Noncontrolling interests related to the acquisition of a business contributed to a consolidated Latin American venture					20,250,000
Noncontrolling interests created by a decrease in the ownership of a subsidiary contributed to a consolidated Latin American venture					15,750,000
Decrease in redeemable noncontrolling interests in a consolidated Latin American venture, resulting from the acquisition of Meetic S.A. ("Meetic")			(37,917,000)
Noncontrolling interests related to other acquisitions					3,333,000
Net earnings (loss) attributable to noncontrolling interests			1,278,000		(5,007,000)
Change in fair value of redeemable noncontrolling interests			1,516,000		(2,059,000)
Other			128,000		(578,000)
Balance at the end of the period	19,095,000		19,095,000		59,869,000
Accumulated other comprehensive income
Foreign currency translation adjustment, net of tax	(7,574,000)		(7,574,000)		16,027,000
Unrealized gains on available-for-sale securities, net of tax	19,711,000		19,711,000		1,519,000
Accumulated other comprehensive income, net of tax	12,137,000		12,137,000		17,546,000
Other income, net
Interest income	1,224,000	1,550,000	3,676,000	4,851,000
Interest expense	(1,425,000)	(1,321,000)	(4,135,000)	(3,967,000)
Gain on sales of investments	317,000		1,861,000	3,989,000
Non-income tax refunds related to Match Europe			4,630,000
Foreign currency exchange gains, net	3,748,000	371,000	4,050,000	292,000
Other	444,000	219,000	615,000	993,000
Other income, net	4,308,000	819,000	10,697,000	6,158,000
Comprehensive income (loss)
Net earnings	64,051,000	17,645,000	125,413,000	11,156,000
Change in foreign currency translation adjustment, net of tax	(39,675,000)	1,195,000	(29,813,000)	(12,468,000)
Change in net unrealized (losses) gains on available-for-sale securities, net of tax	(16,624,000)	3,636,000	18,192,000	(4,106,000)
Other comprehensive (loss) income	(56,299,000)	4,831,000	(11,621,000)	(16,574,000)
Unrealized gains, net of tax, reclassified out of accumulated other comprehensive income into other income, net	600,000	200,000	2,000,000	2,900,000
Comprehensive income (loss)	7,752,000	22,476,000	113,792,000	(5,418,000)
Net loss (earnings) attributable to noncontrolling interests	922,000	(136,000)	54,000	1,239,000
Change in foreign currency translation adjustment, net of tax, attributable to noncontrolling interests	6,212,000		6,212,000
Comprehensive loss (income) attributable to noncontrolling interests	7,134,000	(136,000)	6,266,000	1,239,000
Comprehensive income (loss) attributable to IAC shareholders	14,886,000	22,340,000	120,058,000	(4,179,000)
Buildings and leasehold improvements
Property and equipment, net
Property and equipment, gross	235,524,000		235,524,000		234,328,000
Computer equipment and capitalized software
Property and equipment, net
Property and equipment, gross	198,415,000		198,415,000		183,055,000
Furniture and other equipment
Property and equipment, net
Property and equipment, gross	42,554,000		42,554,000		41,930,000
Projects in progress
Property and equipment, net
Property and equipment, gross	5,393,000		5,393,000		2,944,000
Land
Property and equipment, net
Property and equipment, gross	$ 5,117,000		$ 5,117,000		$ 5,117,000