GUARANTOR AND NON-GUARANTOR FINANCIAL INFORMATION (Details2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Revenue	$ 742,249	$ 640,600
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	255,082	223,571
Selling and marketing expense	242,914	219,838
General and administrative expense	98,026	91,788
Product development expense	33,582	23,482
Depreciation	14,016	12,115
Amortization of intangibles	14,078	7,041
Total costs and expenses	657,698	577,835
Operating income	84,551	62,765
Equity in losses of unconsolidated affiliates	(91)	(5,901)
Interest expense	(7,663)	(1,347)
Other income, net	1,658	2,756
Earnings from continuing operations before income taxes	78,455	58,273
Income tax provision	(25,746)	(27,120)
Earnings from continuing operations	52,709	31,153
(Loss) earnings from discontinued operations, net of tax	(944)	3,684
Net earnings	51,765	34,837
Net loss (earnings) attributable to noncontrolling interests	1,872	(359)
Net earnings attributable to IAC shareholders	53,637	34,478
Comprehensive income attributable to IAC shareholders	41,710	65,374
IAC
Condensed Financial Statements, Captions [Line Items]
Revenue	0
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	677
Selling and marketing expense	431
General and administrative expense	22,245
Product development expense	899
Depreciation	367
Amortization of intangibles	0
Total costs and expenses	24,619
Operating income	(24,619)
Equity in losses of unconsolidated affiliates	113,783
Interest expense	(6,557)
Other income, net	(55,448)
Earnings from continuing operations before income taxes	27,159
Income tax provision	27,422
Earnings from continuing operations	54,581
(Loss) earnings from discontinued operations, net of tax	(944)
Net earnings	53,637
Net loss (earnings) attributable to noncontrolling interests	0
Net earnings attributable to IAC shareholders	53,637
Comprehensive income attributable to IAC shareholders	41,710
Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenue	515,784
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	152,905
Selling and marketing expense	170,667
General and administrative expense	41,147
Product development expense	21,279
Depreciation	8,624
Amortization of intangibles	8,910
Total costs and expenses	403,532
Operating income	112,252
Equity in losses of unconsolidated affiliates	2,771
Interest expense	(1,065)
Other income, net	(18,730)
Earnings from continuing operations before income taxes	95,228
Income tax provision	(33,332)
Earnings from continuing operations	61,896
(Loss) earnings from discontinued operations, net of tax	0
Net earnings	61,896
Net loss (earnings) attributable to noncontrolling interests	8
Net earnings attributable to IAC shareholders	61,904
Comprehensive income attributable to IAC shareholders	61,829
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenue	227,502
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	102,279
Selling and marketing expense	72,073
General and administrative expense	34,635
Product development expense	11,404
Depreciation	5,025
Amortization of intangibles	5,168
Total costs and expenses	230,584
Operating income	(3,082)
Equity in losses of unconsolidated affiliates	(91)
Interest expense	(41)
Other income, net	75,836
Earnings from continuing operations before income taxes	72,622
Income tax provision	(19,836)
Earnings from continuing operations	52,786
(Loss) earnings from discontinued operations, net of tax	7
Net earnings	52,793
Net loss (earnings) attributable to noncontrolling interests	1,864
Net earnings attributable to IAC shareholders	54,657
Comprehensive income attributable to IAC shareholders	49,313
Total Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenue	(1,037)
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	(779)
Selling and marketing expense	(257)
General and administrative expense	(1)
Product development expense	0
Depreciation	0
Amortization of intangibles	0
Total costs and expenses	(1,037)
Operating income	0
Equity in losses of unconsolidated affiliates	(116,554)
Interest expense	0
Other income, net	0
Earnings from continuing operations before income taxes	(116,554)
Income tax provision	0
Earnings from continuing operations	(116,554)
(Loss) earnings from discontinued operations, net of tax	(7)
Net earnings	(116,561)
Net loss (earnings) attributable to noncontrolling interests	0
Net earnings attributable to IAC shareholders	(116,561)
Comprehensive income attributable to IAC shareholders	(111,142)
IAC Consolidated
Condensed Financial Statements, Captions [Line Items]
Revenue	742,249
Costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	255,082
Selling and marketing expense	242,914
General and administrative expense	98,026
Product development expense	33,582
Depreciation	14,016
Amortization of intangibles	14,078
Total costs and expenses	657,698
Operating income	84,551
Equity in losses of unconsolidated affiliates	(91)
Interest expense	(7,663)
Other income, net	1,658
Earnings from continuing operations before income taxes	78,455
Income tax provision	(25,746)
Earnings from continuing operations	52,709
(Loss) earnings from discontinued operations, net of tax	(944)
Net earnings	51,765
Net loss (earnings) attributable to noncontrolling interests	1,872
Net earnings attributable to IAC shareholders	53,637
Comprehensive income attributable to IAC shareholders	$ 41,710