THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained earnings	$ 1,067,042	$ 1,067,042		$ 595,038
Deferred tax liability	34,861	34,861		35,070
Deferred revenue	381,397	381,397		342,483
Unrealized (losses) gains, net, on equity securities held	$ (115)	126,444
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 (losses) gains, net, on equity securities held		$ 126,400
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