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LONG-TERM DEBT - Summary (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 04, 2017	Oct. 02, 2017	Jun. 01, 2016
Debt Instrument
Total long-term debt	$ 2,348,239,000
Less: unamortized original issue discount	61,377,000
Less: unamortized debt issuance costs	27,564,000
Less: Current portion of long-term debt	13,750,000	$ 13,750,000
Long-term debt, net	2,245,548,000	1,979,469,000
IAC
Debt Instrument
Total long-term debt	551,989,000	552,359,000
Less: unamortized original issue discount	54,025,000	67,158,000
Less: unamortized debt issuance costs	13,298,000	16,740,000
Long-term debt, net	484,666,000	468,461,000
IAC \| Senior Notes
Debt Instrument
Total long-term debt	463,500,000	450,300,000		$ 517,500,000.0
Less: unamortized original issue discount	54,000,000	67,200,000
IAC \| Senior Notes \| 0.875% Exchangeable Senior Notes due October 1, 2022 (the Exchangeable Notes); interest payable each April 1 and October 1
Debt Instrument
Total long-term debt	$ 517,500,000	$ 517,500,000
Stated interest rate (as a percent)	0.875%	0.875%		0.875%
IAC \| Senior Notes \| 4.75% Senior Notes due December 15, 2022 (the 4.75% Senior Notes); interest payable each June 15 and December 15
Debt Instrument
Total long-term debt	$ 34,489,000	$ 34,859,000
Stated interest rate (as a percent)	4.75%	4.75%
Match Group
Debt Instrument
Total long-term debt	$ 1,535,000,000	$ 1,275,000,000
Less: unamortized original issue discount	7,352,000	8,668,000
Less: unamortized debt issuance costs	11,737,000	13,636,000
Long-term debt, net	1,515,911,000	1,252,696,000
Match Group \| Senior Notes \| 6.375% Senior Notes due June 1, 2024 (the 6.375% MTCH Senior Notes); interest payable each June 1 and December 1
Debt Instrument
Total long-term debt	$ 400,000,000	$ 400,000,000
Stated interest rate (as a percent)	6.375%	6.375%			6.375%
Match Group \| Senior Notes \| 5.00% Senior Notes due December 15, 2027 (the 5.00% MTCH Senior Notes); interest payable each June 15 and December 15
Debt Instrument
Total long-term debt	$ 450,000,000	$ 450,000,000
Stated interest rate (as a percent)	5.00%	5.00%	5.00%
Match Group \| Term Loan \| MTCH Term Loan due November 16, 2022
Debt Instrument
Total long-term debt	$ 425,000,000	$ 425,000,000
Match Group \| Credit Facility \| MTCH Credit Facility due December 7, 2023
Debt Instrument
Total long-term debt	260,000,000	0
ANGI Homeservices
Debt Instrument
Less: unamortized debt issuance costs	2,529,000	2,938,000
Less: Current portion of long-term debt	13,750,000	13,750,000
Long-term debt, net	244,971,000	258,312,000
ANGI Homeservices \| Term Loan \| ANGI Term Loan due November 5, 2023
Debt Instrument
Total long-term debt	$ 261,250,000	$ 275,000,000