THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 1,059,122	$ 767,387	$ 2,054,197	$ 1,528,220
Operating costs and expenses	890,685	691,752	1,795,810	1,415,525
Operating income (loss)	168,437	75,635	258,387	112,695
Net earnings	280,854	80,557	368,693	109,020
Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	1,061,151		2,056,185
Operating costs and expenses	892,097		1,803,023
Operating income (loss)	169,054		253,162
Net earnings	281,269		364,786
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(2,029)		(1,988)
Operating costs and expenses	(1,412)		(7,213)
Operating income (loss)	(617)		5,225
Net earnings	(415)		3,907
Operating segments | Match Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	421,196	309,572	828,563	608,336
Operating costs and expenses	271,031		566,165
Operating income (loss)	150,165	82,975	262,398	141,846
Operating segments | Match Group | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	421,196		828,563
Operating costs and expenses	271,031		566,165
Operating income (loss)	150,165		262,398
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	294,822	180,711	550,133	331,456
Operating costs and expenses	271,560		537,627
Operating income (loss)	23,262	(4,141)	12,506	(2,753)
Operating segments | ANGI Homeservices | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	294,822		550,133
Operating costs and expenses	273,678		545,838
Operating income (loss)	21,144		4,295
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	(2,118)		(8,211)
Operating income (loss)	2,118		8,211
Operating segments | Video
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	62,757	55,182	128,919	105,759
Operating costs and expenses	77,739		159,776
Operating income (loss)	(14,982)	(7,829)	(30,857)	(23,418)
Operating segments | Video | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	63,018		129,609
Operating costs and expenses	77,739		160,003
Operating income (loss)	(14,721)		(30,394)
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	(261)		(690)
Operating costs and expenses	0		(227)
Operating income (loss)	(261)		(463)
Operating segments | Applications
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	143,074	143,969	275,061	302,866
Operating costs and expenses	109,997		216,523
Operating income (loss)	33,077	39,134	58,538	71,902
Operating segments | Applications | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	144,842		276,359
Operating costs and expenses	109,291		215,298
Operating income (loss)	35,551		61,061
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	(1,768)		(1,298)
Operating costs and expenses	706		1,225
Operating income (loss)	(2,474)		(2,523)
Operating segments | Publishing
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	137,355	78,124	271,677	156,204
Operating costs and expenses	124,548		243,059
Operating income (loss)	12,807	(2,857)	28,618	(8,645)
Operating segments | Publishing | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	137,355		271,677
Operating costs and expenses	124,548		243,059
Operating income (loss)	12,807		28,618
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)	0	0	0	(5,621)
Inter-segment eliminations
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(82)	(171)	(156)	(381)
Inter-segment eliminations | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(82)		(156)
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	35,810		72,660
Operating income (loss)	(35,892)	$ (31,647)	(72,816)	$ (60,616)
Corporate | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	35,810		72,660
Operating income (loss)	(35,892)		(72,816)
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