SEGMENT INFORMATION - Revenue Disaggregated by Service (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenues	$ 1,217,680	$ 1,246,874	$ 1,186,658	$ 1,105,843	$ 1,104,103	$ 1,104,592	$ 1,059,122	$ 995,075	$ 4,757,055	$ 4,262,892	$ 3,307,239
Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenues									2,051,258	1,729,850	1,330,661
Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,326,205	1,132,241	736,386
Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									196,015	159,641	103,332
Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									167,594	130,991	90,890
Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									519,459	582,287	577,998
Operating Segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenues									199,224	123,516	55,849
Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									496,832	528,250	468,589
North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									1,249,892	1,062,171	678,897
Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									76,313	70,070	57,489
Direct | Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenues									2,007,174	1,677,171	1,281,249
Direct | Operating Segments | Match Group | Tinder
Segment Reporting Information [Line Items]
Revenues									1,152,045	805,316	403,216
Direct | Operating Segments | Match Group | Other brands
Segment Reporting Information [Line Items]
Revenues									855,129	871,855	878,033
Direct | North America | Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenues									1,024,161	902,478	741,334
Direct | International | Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenues									983,013	774,693	539,915
Indirect | Operating Segments | Match Group
Segment Reporting Information [Line Items]
Revenues									44,084	52,679	49,412
Marketplace | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									985,210	774,495	581,414
Consumer connection revenue | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									913,533	704,341	521,481
Service professional membership subscription revenue | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									64,706	66,214	56,135
Other revenue | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									6,971	3,940	3,798
Advertising and other revenue | North America | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									264,682	287,676	97,483
Advertising and other revenue | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									2,471	1,795	884
Consumer connection revenue | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									59,611	50,913	40,009
Service professional membership subscription revenue | Europe | Operating Segments | ANGI Homeservices
Segment Reporting Information [Line Items]
Revenues									14,231	17,362	16,596
Platform revenue | Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									193,736	146,665	99,650
Hardware revenue | Operating Segments | Vimeo
Segment Reporting Information [Line Items]
Revenues									2,279	12,976	3,682
Advertising | Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									126,487	103,704	76,316
Advertising | Operating Segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenues									9,346	18,541	27,869
Advertising | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									437,459	424,485	279,487
Google advertising revenue | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									391,709	357,752	225,576
Non-Google advertising revenue | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									45,750	66,733	53,911
Affiliate Commerce Commission | Operating Segments | Dotdash
Segment Reporting Information [Line Items]
Revenues									41,107	27,287	14,574
Other revenue | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									59,373	103,765	169,497
Desktop | Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									320,235	458,771	522,149
Advertising | Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									304,377	437,956	487,536
Google advertising revenue | Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									291,215	426,964	480,774
Non-Google advertising revenue | Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									13,162	10,992	6,762
Subscription and other revenue | Operating Segments | Applications
Segment Reporting Information [Line Items]
Revenues									15,858	20,815	34,613
Subscription and other revenue | Operating Segments | Applications | Mosaic Group
Segment Reporting Information [Line Items]
Revenues									189,878	104,975	27,980
Test preparation revenue | Operating Segments | Emerging & Other
Segment Reporting Information [Line Items]
Revenues									$ 0	$ 0	$ 19,605