SEGMENT INFORMATION - Segment Reporting Information (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenue	$ 1,104,103	$ 1,104,592	$ 1,059,122	$ 995,075	$ 950,585	$ 828,434	$ 767,387	$ 760,833	$ 4,262,892	$ 3,307,239	$ 3,139,882
Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenue									1,729,850	1,330,661	1,118,110
Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenue									1,132,241	736,386	498,890
Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenue									159,641	103,332	78,805
Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenue									130,991	90,890	77,913
Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenue									582,287	577,998	604,140
Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenue									528,250	468,589	762,609
Inter-segment elimination
Segment Reporting Information [Line Items]
Revenue									$ (368)	$ (617)	$ (585)