CONSOLIDATED STATEMENT OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue	$ 3,109,547us-gaap_Revenues	$ 3,022,987us-gaap_Revenues	$ 2,800,933us-gaap_Revenues
Operating costs and expenses:
Cost of revenue (exclusive of depreciation shown separately below)	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	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	234,557	281,799	169,847
Earnings (loss) from discontinued operations, net of tax	174,673	1,926	(9,051)
Net earnings	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	414,873	285,784	159,266
Per share information attributable to IAC shareholders:
Basic earnings per share from continuing operations (in dollars per share)	$ 2.88	$ 3.40	$ 1.95
Diluted earnings per share from continuing operations (in dollars per share)	$ 2.71	$ 3.27	$ 1.81
Basic earnings per share (in dollars per share)	$ 4.98us-gaap_EarningsPerShareBasic	$ 3.42us-gaap_EarningsPerShareBasic	$ 1.85us-gaap_EarningsPerShareBasic
Diluted earnings per share (in dollars per share)	$ 4.68us-gaap_EarningsPerShareDiluted	$ 3.29us-gaap_EarningsPerShareDiluted	$ 1.71us-gaap_EarningsPerShareDiluted
Dividends declared per share (in dollars per share)	$ 1.16	$ 0.96	$ 0.72
Non-cash compensation expense by function:
Total non-cash compensation expense	59,634	53,005	85,625
Cost of revenue
Non-cash compensation expense by function:
Total non-cash compensation expense	949	2,863	6,219
Selling and marketing expense
Non-cash compensation expense by function:
Total non-cash compensation expense	2,144	2,813	4,760
General and administrative expense
Non-cash compensation expense by function:
Total non-cash compensation expense	49,862	42,487	68,640
Product development expense
Non-cash compensation expense by function:
Total non-cash compensation expense	$ 6,679	$ 4,842	$ 6,006

Name:	iaci_NonCashCompensationExpenseByFunctionAbstract
Namespace Prefix:	iaci_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.