THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,104,592	$ 828,434	$ 3,158,789	$ 2,356,654
Operating costs and expenses	931,760	847,023	2,727,570	2,262,548
Operating income (loss)	172,832	(18,589)	431,219	94,106
Net earnings	171,577	225,639	540,270	334,659
Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	1,104,729		3,159,810
Operating costs and expenses	930,854		2,733,983
Operating income (loss)	173,875		425,827
Net earnings	172,235		536,119
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(137)		(1,021)
Operating costs and expenses	906		(6,413)
Operating income (loss)	(1,043)		5,392
Net earnings	(658)		4,151
Operating segments | Match Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	443,943	343,418	1,272,506	951,754
Operating costs and expenses	304,048		870,213
Operating income (loss)	139,895	91,008	402,293	232,854
Operating segments | Match Group | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	443,943		1,272,506
Operating costs and expenses	304,048		870,213
Operating income (loss)	139,895		402,293
Operating segments | Match Group | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0		0
Operating costs and expenses	0		0
Operating income (loss)	0		0
Operating segments | ANGI Homeservices
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	303,116	181,717	853,249	513,173
Operating costs and expenses	269,601		807,228
Operating income (loss)	33,515	(112,505)	46,021	(115,258)
Operating segments | ANGI Homeservices | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	303,116		853,249
Operating costs and expenses	269,352		815,190
Operating income (loss)	33,764		38,059
Operating segments | ANGI Homeservices | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0		0
Operating costs and expenses	249		(7,962)
Operating income (loss)	(249)		7,962
Operating segments | Video
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	64,193	78,338	193,112	184,097
Operating costs and expenses	74,443		234,219
Operating income (loss)	(10,250)	(1,809)	(41,107)	(25,227)
Operating segments | Video | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	64,440		194,049
Operating costs and expenses	74,756		234,941
Operating income (loss)	(10,316)		(40,892)
Operating segments | Video | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(247)		(937)
Operating costs and expenses	(313)		(722)
Operating income (loss)	66		(215)
Operating segments | Applications
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	153,973	136,333	429,034	439,199
Operating costs and expenses	120,932		337,455
Operating income (loss)	33,041	29,386	91,579	101,288
Operating segments | Applications | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	153,863		429,118
Operating costs and expenses	119,962		335,184
Operating income (loss)	33,901		93,934
Operating segments | Applications | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	110		(84)
Operating costs and expenses	970		2,271
Operating income (loss)	(860)		(2,355)
Operating segments | Publishing
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	139,439	88,755	411,116	244,959
Operating costs and expenses	122,041		365,100
Operating income (loss)	17,398	5,677	46,016	(2,968)
Operating segments | Publishing | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	139,439		411,116
Operating costs and expenses	122,041		365,100
Operating income (loss)	17,398		46,016
Operating segments | Publishing | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0		0
Operating costs and expenses	0		0
Operating income (loss)	0		0
Operating segments | Other
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue				23,980
Operating income (loss)				(5,621)
Inter-segment eliminations
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(72)	(127)	(228)	(508)
Inter-segment eliminations | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(72)		(228)
Inter-segment eliminations | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0		0
Corporate
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	40,695		113,355
Operating income (loss)	(40,767)	$ (30,346)	(113,583)	$ (90,962)
Corporate | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	40,695		113,355
Operating income (loss)	(40,767)		(113,583)
Corporate | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	0		0
Operating income (loss)	$ 0		$ 0