SEGMENT INFORMATION - Revenue Disaggregated by Service (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Revenue	$ 1,186,658	$ 1,059,122	$ 2,292,501	$ 2,054,197
Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	497,973	421,196	962,598	828,563
Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	343,896	294,822	647,339	550,133
Operating segments | Vimeo
Segment Reporting Information [Line Items]
Revenue	45,713	39,560	89,294	75,128
Operating segments | Dotdash
Segment Reporting Information [Line Items]
Revenue	37,728	30,757	71,689	60,788
Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	132,937	143,074	276,486	275,061
Operating segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenue	48,098	28,644	95,661	43,043
Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	128,542	129,796	245,290	264,681
North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	324,400	277,505	606,394	513,531
International
Segment Reporting Information [Line Items]
Revenue	412,563	350,551	806,025	688,046
Europe | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	19,496	17,317	40,945	36,602
Direct revenue | Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	487,300	407,727	941,262	800,464
Direct revenue | North America | Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	251,499	222,163	489,272	433,520
Direct revenue | International | Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	235,801	185,564	451,990	366,944
Indirect revenue | Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	10,673	13,469	21,336	28,099
Marketplace revenue | North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	259,528	204,735	479,453	370,343
Consumer connection revenue | North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	241,236	187,172	442,818	336,232
Membership subscription revenue | North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	16,485	16,565	33,002	32,192
Other revenue | North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	1,807	998	3,633	1,919
Consumer connection revenue | Europe | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	15,232	12,496	32,355	26,863
Membership subscription revenue | Europe | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	3,613	4,517	7,355	9,188
Advertising and other revenue | North America | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	64,872	72,770	126,941	143,188
Advertising and other revenue | Europe | Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	651	304	1,235	551
Platform revenue | Operating segments | Vimeo
Segment Reporting Information [Line Items]
Revenue	45,713	36,293	87,015	69,225
Hardware revenue | Operating segments | Vimeo
Segment Reporting Information [Line Items]
Revenue	0	3,267	2,279	5,903
Advertising revenue | Operating segments | Dotdash
Segment Reporting Information [Line Items]
Revenue	29,005	24,552	55,013	47,765
Advertising revenue | Operating segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenue	2,418	5,123	4,833	10,513
Advertising revenue | Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	113,624	105,154	216,874	211,174
Google advertising revenue | Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	105,325	88,355	201,598	181,106
Other | Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	8,299	16,799	15,276	30,068
Affiliate commerce commission and other revenue | Operating segments | Dotdash
Segment Reporting Information [Line Items]
Revenue	8,723	6,205	16,676	13,023
Other revenue | Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	14,918	24,642	28,416	53,507
Subscription and other revenue | Operating segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenue	45,680	23,521	90,828	32,530
Desktop | Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	84,839	114,430	180,825	232,018
Advertising revenue | Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	80,931	109,662	172,329	219,934
Google advertising revenue | Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	78,085	107,550	166,135	216,127
Other | Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	2,846	2,112	6,194	3,807
Subscription and other revenue | Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	$ 3,908	$ 4,768	$ 8,496	$ 12,084