CONSOLIDATED STATEMENT OF COMPREHENSIVE OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 280,854	$ 80,557	$ 368,693	$ 109,020
Other comprehensive income, net of tax:
Change in foreign currency translation adjustment	(46,576)	18,788	(11,183)	40,698
Change in unrealized gains and losses of available-for-sale securities (net of tax provision of $4 for both the three and six months ended June 30, 2018, and net of tax benefit of $3,846 for both the three and six months ended June 30, 2017)	13	(4,028)	13	(4,026)
Total other comprehensive (loss) income	(46,563)	14,760	(11,170)	36,672
Comprehensive income, net of tax	234,291	95,317	357,523	145,692
Components of comprehensive income attributable to noncontrolling interests:
Net earnings attributable to noncontrolling interests	(62,501)	(14,289)	(79,258)	(16,543)
Change in foreign currency translation adjustment attributable to noncontrolling interests	9,119	(4,153)	2,083	(7,287)
Comprehensive income attributable to noncontrolling interests	(53,382)	(18,442)	(77,175)	(23,830)
Comprehensive income attributable to IAC shareholders	$ 180,909	$ 76,875	$ 280,348	$ 121,862