BUSINESS COMBINATION (Details)	3 Months Ended	9 Months Ended	0 Months Ended		0 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2012 USD ($)	Jan. 04, 2013 Twoo USD ($)	Jan. 04, 2013 Twoo EUR (€)	Sep. 24, 2012 About Group USD ($) topic	Sep. 30, 2012 About Group USD ($)	Sep. 30, 2012 About Group USD ($)
Business Combination
Purchase price, cash paid			$ 25,000,000		$ 300,000,000
Business Combination, Contingent Consideration Arrangements, Range of Outcomes, Value, High			112,200,000	83,200,000
Contingent consideration, fair value			40,800,000
Number of topics in the online liabrary					90,000
Purchase of net working capital					17,100,000
Pro forma financial information
Adjustment for amortization of intangible assets						4,600,000	14,100,000
Revenue	740,086,000	2,110,653,000
Net earnings attributable to IAC shareholders	$ 43,909,000	$ 125,722,000
Basic earnings per share attributable to IAC shareholders (in dollars per share)	$ 0.50	$ 1.47
Diluted earnings per share attributable to IAC shareholders (in dollars per share)	$ 0.46	$ 1.35