CONSOLIDATED STATEMENT OF COMPREHENSIVE OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net earnings	$ 543,820	$ 757,747	$ 358,008
Other comprehensive (loss) income, net of income taxes:
Change in foreign currency translation adjustment	(9,961)	(31,411)	80,269
Change in unrealized gains and losses on available-for-sale securities (net of tax benefit of $3,846 in 2017)	(5)	5	(4,026)
Total other comprehensive (loss) income, net of income taxes	(9,966)	(31,406)	76,243
Comprehensive income, net of income taxes	533,854	726,341	434,251
Components of comprehensive (income) loss attributable to noncontrolling interests:
Net earnings attributable to noncontrolling interests	(112,689)	(130,786)	(53,084)
Change in foreign currency translation adjustment attributable to noncontrolling interests	2,023	6,129	(13,797)
Change in unrealized gains and losses of available-for-sale securities attributable to noncontrolling interests	1	(1)	0
Comprehensive income attributable to noncontrolling interests	(110,665)	(124,658)	(66,881)
Comprehensive income attributable to IAC shareholders	$ 423,189	$ 601,683	$ 367,370