The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Name:	us-gaap_AmortizationOfIntangibleAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

GUARANTOR AND NONGUARANTOR FINANCIAL INFORMATION (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Income Statements, Captions [Line Items]
Revenue	$ 830,754us-gaap_Revenues	$ 782,231us-gaap_Revenues	$ 756,315us-gaap_Revenues	$ 740,247us-gaap_Revenues	$ 724,455us-gaap_Revenues	$ 756,872us-gaap_Revenues	$ 799,411us-gaap_Revenues	$ 742,249us-gaap_Revenues	$ 3,109,547us-gaap_Revenues	$ 3,022,987us-gaap_Revenues	$ 2,800,933us-gaap_Revenues
Cost of revenue	238,517us-gaap_CostOfGoodsAndServicesSold	224,695us-gaap_CostOfGoodsAndServicesSold	210,730us-gaap_CostOfGoodsAndServicesSold	209,234us-gaap_CostOfGoodsAndServicesSold	222,421us-gaap_CostOfGoodsAndServicesSold	249,888us-gaap_CostOfGoodsAndServicesSold	273,938us-gaap_CostOfGoodsAndServicesSold	257,474us-gaap_CostOfGoodsAndServicesSold	883,176us-gaap_CostOfGoodsAndServicesSold	1,003,721us-gaap_CostOfGoodsAndServicesSold	991,688us-gaap_CostOfGoodsAndServicesSold
Selling and marketing expense									1,124,437us-gaap_SellingAndMarketingExpense	956,410us-gaap_SellingAndMarketingExpense	894,438us-gaap_SellingAndMarketingExpense
General and administrative expense									443,610us-gaap_GeneralAndAdministrativeExpense	378,142us-gaap_GeneralAndAdministrativeExpense	386,461us-gaap_GeneralAndAdministrativeExpense
Product development expense									160,515us-gaap_ResearchAndDevelopmentExpense	139,759us-gaap_ResearchAndDevelopmentExpense	116,526us-gaap_ResearchAndDevelopmentExpense
Depreciation									61,156us-gaap_Depreciation	58,909us-gaap_Depreciation	52,481us-gaap_Depreciation
Amortization of intangibles									57,926us-gaap_AmortizationOfIntangibleAssets	59,843us-gaap_AmortizationOfIntangibleAssets	35,771us-gaap_AmortizationOfIntangibleAssets
Total operating costs and expenses									2,730,820us-gaap_CostsAndExpenses	2,596,784us-gaap_CostsAndExpenses	2,477,365us-gaap_CostsAndExpenses
Operating income	110,372us-gaap_OperatingIncomeLoss	100,953us-gaap_OperatingIncomeLoss	95,690us-gaap_OperatingIncomeLoss	71,712us-gaap_OperatingIncomeLoss	112,952us-gaap_OperatingIncomeLoss	122,004us-gaap_OperatingIncomeLoss	106,696us-gaap_OperatingIncomeLoss	84,551us-gaap_OperatingIncomeLoss	378,727us-gaap_OperatingIncomeLoss	426,203us-gaap_OperatingIncomeLoss	323,568us-gaap_OperatingIncomeLoss
Equity in losses of unconsolidated affiliates									(9,697)	(6,615)	(25,345)
Interest expense									(56,314)us-gaap_InterestExpense	(33,596)us-gaap_InterestExpense	(6,149)us-gaap_InterestExpense
Other (expense) income, net									(42,787)us-gaap_NonoperatingIncomeExpense	30,309us-gaap_NonoperatingIncomeExpense	(3,012)us-gaap_NonoperatingIncomeExpense
Earnings from continuing operations before income taxes									269,929	416,301	289,062
Income tax provision									(35,372)us-gaap_IncomeTaxExpenseBenefit	(134,502)us-gaap_IncomeTaxExpenseBenefit	(119,215)us-gaap_IncomeTaxExpenseBenefit
Earnings from continuing operations	67,986	150,261	(17,995)	34,305	78,829	91,721	58,540	52,709	234,557	281,799	169,847
Less: earnings (loss) from discontinued operations, net of tax	625	175,730	(868)	(814)	24	3,914	(1,068)	(944)	174,673	1,926	(9,051)
Net earnings	68,611us-gaap_ProfitLoss	325,991us-gaap_ProfitLoss	(18,863)us-gaap_ProfitLoss	33,491us-gaap_ProfitLoss	78,853us-gaap_ProfitLoss	95,635us-gaap_ProfitLoss	57,472us-gaap_ProfitLoss	51,765us-gaap_ProfitLoss	409,230us-gaap_ProfitLoss	283,725us-gaap_ProfitLoss	160,796us-gaap_ProfitLoss
Net loss (earnings) attributable to noncontrolling interests									5,643	2,059	(1,530)
Net earnings attributable to IAC shareholders	70,172	326,812	(17,996)	35,885	76,917	96,940	58,290	53,637	414,873	285,784	159,266
Comprehensive income attributable to IAC shareholders									340,219us-gaap_ComprehensiveIncomeNetOfTax	304,907us-gaap_ComprehensiveIncomeNetOfTax	139,540us-gaap_ComprehensiveIncomeNetOfTax
IAC
Condensed Income Statements, Captions [Line Items]
Revenue									0	0	0
Cost of revenue									998	2,456	5,194
Selling and marketing expense									2,138	2,563	4,081
General and administrative expense									105,221	97,025	121,919
Product development expense									6,496	4,685	5,611
Depreciation									1,426	1,386	832
Amortization of intangibles									0	0	0
Total operating costs and expenses									116,279	108,115	137,637
Operating income									(116,279)	(108,115)	(137,637)
Equity in losses of unconsolidated affiliates									253,582	439,925	309,639
Interest expense									(51,988)	(29,417)	(1,835)
Other (expense) income, net									2,688	(35,331)	(82,900)
Earnings from continuing operations before income taxes									88,003	267,062	87,267
Income tax provision									152,197	16,796	81,050
Earnings from continuing operations									240,200	283,858	168,317
Less: earnings (loss) from discontinued operations, net of tax									174,673	1,926	(9,051)
Net earnings									414,873	285,784	159,266
Net loss (earnings) attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									414,873	285,784	159,266
Comprehensive income attributable to IAC shareholders									340,219	304,907	139,540
Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue									2,286,621	2,183,969	1,986,527
Cost of revenue									525,185	600,511	597,588
Selling and marketing expense									904,221	769,115	669,448
General and administrative expense									211,293	164,173	152,166
Product development expense									110,375	100,350	83,008
Depreciation									40,645	38,938	35,544
Amortization of intangibles									37,661	40,277	10,958
Total operating costs and expenses									1,829,380	1,713,364	1,548,712
Operating income									457,241	470,605	437,815
Equity in losses of unconsolidated affiliates									34,613	62,402	37,866
Interest expense									(4,246)	(3,979)	(4,174)
Other (expense) income, net									(3,315)	(35,040)	(3,733)
Earnings from continuing operations before income taxes									484,293	493,988	467,774
Income tax provision									(172,128)	(156,170)	(146,333)
Earnings from continuing operations									312,165	337,818	321,441
Less: earnings (loss) from discontinued operations, net of tax									0	0	0
Net earnings									312,165	337,818	321,441
Net loss (earnings) attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									312,165	337,818	321,441
Comprehensive income attributable to IAC shareholders									303,976	338,683	322,212
Non-Guarantor Subsidiaries
Condensed Income Statements, Captions [Line Items]
Revenue									834,765	843,133	820,759
Cost of revenue									359,746	403,614	393,811
Selling and marketing expense									226,381	185,865	222,374
General and administrative expense									127,051	117,066	112,359
Product development expense									44,472	34,724	27,907
Depreciation									19,085	18,585	16,105
Amortization of intangibles									20,265	19,566	24,813
Total operating costs and expenses									797,000	779,420	797,369
Operating income									37,765	63,713	23,390
Equity in losses of unconsolidated affiliates									452	(303)	(22,548)
Interest expense									(80)	(200)	(140)
Other (expense) income, net									(42,160)	100,680	83,621
Earnings from continuing operations before income taxes									(4,023)	163,890	84,323
Income tax provision									(15,441)	4,872	(53,932)
Earnings from continuing operations									(19,464)	168,762	30,391
Less: earnings (loss) from discontinued operations, net of tax									570	(39)	842
Net earnings									(18,894)	168,723	31,233
Net loss (earnings) attributable to noncontrolling interests									5,643	2,059	(1,530)
Net earnings attributable to IAC shareholders									(13,251)	170,782	29,703
Comprehensive income attributable to IAC shareholders									(84,767)	181,481	29,828
IAC Consolidated
Condensed Income Statements, Captions [Line Items]
Revenue									3,109,547	3,022,987	2,800,933
Cost of revenue									883,176	1,003,721	991,688
Selling and marketing expense									1,124,437	956,410	894,438
General and administrative expense									443,610	378,142	386,461
Product development expense									160,515	139,759	116,526
Depreciation									61,156	58,909	52,481
Amortization of intangibles									57,926	59,843	35,771
Total operating costs and expenses									2,730,820	2,596,784	2,477,365
Operating income									378,727	426,203	323,568
Equity in losses of unconsolidated affiliates									(9,697)	(6,615)	(25,345)
Interest expense									(56,314)	(33,596)	(6,149)
Other (expense) income, net									(42,787)	30,309	(3,012)
Earnings from continuing operations before income taxes									269,929	416,301	289,062
Income tax provision									(35,372)	(134,502)	(119,215)
Earnings from continuing operations									234,557	281,799	169,847
Less: earnings (loss) from discontinued operations, net of tax									174,673	1,926	(9,051)
Net earnings									409,230	283,725	160,796
Net loss (earnings) attributable to noncontrolling interests									5,643	2,059	(1,530)
Net earnings attributable to IAC shareholders									414,873	285,784	159,266
Comprehensive income attributable to IAC shareholders									340,219	304,907	139,540
Eliminations
Condensed Income Statements, Captions [Line Items]
Revenue									(11,839)	(4,115)	(6,353)
Cost of revenue									(2,753)	(2,860)	(4,905)
Selling and marketing expense									(8,303)	(1,133)	(1,465)
General and administrative expense									45	(122)	17
Product development expense									(828)	0	0
Depreciation									0	0	0
Amortization of intangibles									0	0	0
Total operating costs and expenses									(11,839)	(4,115)	(6,353)
Operating income									0	0	0
Equity in losses of unconsolidated affiliates									(298,344)	(508,639)	(350,302)
Interest expense									0	0	0
Other (expense) income, net									0	0	0
Earnings from continuing operations before income taxes									(298,344)	(508,639)	(350,302)
Income tax provision									0	0	0
Earnings from continuing operations									(298,344)	(508,639)	(350,302)
Less: earnings (loss) from discontinued operations, net of tax									(570)	39	(842)
Net earnings									(298,914)	(508,600)	(351,144)
Net loss (earnings) attributable to noncontrolling interests									0	0	0
Net earnings attributable to IAC shareholders									(298,914)	(508,600)	(351,144)
Comprehensive income attributable to IAC shareholders									$ (219,209)	$ (520,164)	$ (352,040)