CONSOLIDATED STATEMENT OF COMPREHENSIVE OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 171,577	$ 225,639	$ 540,270	$ 334,659
Other comprehensive income, net of tax:
Change in foreign currency translation adjustment	(1,050)	44,126	(12,233)	84,824
Change in unrealized gains and losses on available-for-sale securities (net of tax benefit of $4 for the three months ended September 30, 2018, and net of tax benefit of $3,846 for the nine months ended September 30, 2017)	(28)	0	(15)	(4,026)
Total other comprehensive (loss) income	(1,078)	44,126	(12,248)	80,798
Comprehensive income, net of tax	170,499	269,765	528,022	415,457
Components of comprehensive income attributable to noncontrolling interests:
Net earnings attributable to noncontrolling interests	(25,803)	(45,996)	(105,061)	(62,539)
Change in foreign currency translation adjustment attributable to noncontrolling interests	549	(6,901)	2,632	(14,188)
Comprehensive income attributable to noncontrolling interests	(25,254)	(52,897)	(102,429)	(76,727)
Comprehensive income attributable to IAC shareholders	$ 145,245	$ 216,868	$ 425,593	$ 338,730