THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 921,268		$ 921,268			$ 595,038
Deferred tax liability	35,550		35,550			35,070
Deferred revenue	375,138		375,138			342,483
Unrealized gains, net, on equity securities held	126,414	$ 8,000	126,559	$ 10,600
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					$ 40,200	$ 3,400
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized gains, net, on equity securities held	$ 126,400		$ 126,600
ANGI Homeservices | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					25,900
Current capitalized contract costs					29,700
Noncurrent capitalized contract costs					4,200
Deferred tax liability					8,000
Applications | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings					15,500
Deferred tax liability					4,900
Deferred revenue					$ 20,300