SEGMENT INFORMATION - Financial Data by Segment (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 income (loss)	154,310	168,437	234,183	258,387
Operating segments | Match Group
Segment Reporting Information [Line Items]
Revenue	497,973	421,196	962,598	828,563
Operating income (loss)	172,898	150,165	291,726	262,398
Adjusted EBITDA	203,522	175,561	358,589	313,302
Operating segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue	343,896	294,822	647,339	550,133
Operating income (loss)	11,403	23,262	7,762	12,506
Adjusted EBITDA	51,432	66,979	88,611	103,619
Operating segments | Vimeo
Segment Reporting Information [Line Items]
Revenue	45,713	39,560	89,294	75,128
Operating income (loss)	(11,616)	(9,593)	(29,400)	(19,341)
Adjusted EBITDA	(9,464)	(7,631)	(25,664)	(15,415)
Operating segments | Dotdash
Segment Reporting Information [Line Items]
Revenue	37,728	30,757	71,689	60,788
Operating income (loss)	7,010	1,339	10,057	4,530
Adjusted EBITDA	8,375	1,994	15,525	5,843
Operating segments | Applications
Segment Reporting Information [Line Items]
Revenue	132,937	143,074	276,486	275,061
Operating income (loss)	20,967	33,077	46,323	58,538
Adjusted EBITDA	25,319	35,404	55,007	62,156
Operating segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue	128,542	129,796	245,290	264,681
Operating income (loss)	(1,789)	6,079	(4,309)	12,572
Adjusted EBITDA	(1,517)	8,290	(3,612)	16,498
Inter-segment eliminations
Segment Reporting Information [Line Items]
Revenue	(131)	(83)	(195)	(157)
Corporate
Segment Reporting Information [Line Items]
Operating income (loss)	(44,563)	(35,892)	(87,976)	(72,816)
Adjusted EBITDA	$ (18,586)	$ (15,552)	$ (38,806)	$ (32,560)