THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Adoption of ASU 2014-09 (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	$ 995,075	$ 760,833
Operating costs and expenses	905,125	723,773
Operating income (loss)	89,950	37,060
Net earnings	87,839	28,463
Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	995,034
Operating costs and expenses	910,926
Operating income (loss)	84,108
Net earnings	83,517
Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	41
Operating costs and expenses	(5,801)
Operating income (loss)	5,842
Net earnings	4,322
Operating segments | Match Group
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	407,367	298,764
Operating costs and expenses	295,134
Operating income (loss)	112,233	58,871
Operating segments | Match Group | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	407,367
Operating costs and expenses	295,134
Operating income (loss)	112,233
Operating segments | Match Group | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0
Operating costs and expenses	0
Operating income (loss)	0
Operating segments | ANGI Homeservices
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	255,311	150,745
Operating costs and expenses	266,067
Operating income (loss)	(10,756)	1,388
Operating segments | ANGI Homeservices | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	255,311
Operating costs and expenses	272,160
Operating income (loss)	(16,849)
Operating segments | ANGI Homeservices | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0
Operating costs and expenses	(6,093)
Operating income (loss)	6,093
Operating segments | Video
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	66,162	50,577
Operating costs and expenses	82,037
Operating income (loss)	(15,875)	(15,589)
Operating segments | Video | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	66,591
Operating costs and expenses	82,264
Operating income (loss)	(15,673)
Operating segments | Video | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(429)
Operating costs and expenses	(227)
Operating income (loss)	(202)
Operating segments | Applications
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	131,987	158,897
Operating costs and expenses	106,526
Operating income (loss)	25,461	32,768
Operating segments | Applications | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	131,517
Operating costs and expenses	106,007
Operating income (loss)	25,510
Operating segments | Applications | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	470
Operating costs and expenses	519
Operating income (loss)	(49)
Operating segments | Publishing
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	134,322	78,080
Operating costs and expenses	118,511
Operating income (loss)	15,811	(5,788)
Operating segments | Publishing | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	134,322
Operating costs and expenses	118,511
Operating income (loss)	15,811
Operating segments | Publishing | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0
Operating costs and expenses	0
Operating income (loss)	0
Operating segments | Other
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue		23,980
Operating income (loss)	0	(5,621)
Inter-segment eliminations
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(74)	(210)
Inter-segment eliminations | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	(74)
Inter-segment eliminations | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	0
Corporate
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	36,850
Operating income (loss)	(36,924)	$ (28,969)
Corporate | Under ASC 605
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	36,850
Operating income (loss)	(36,924)
Corporate | Accounting Standards Update 2014-09 | Effect of adoption of ASU No. 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating costs and expenses	0
Operating income (loss)	$ 0