THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) service_professional in Thousands, project in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) operating_segment service_professional project service_category	Mar. 31, 2019 USD ($)	Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Noncontrolling Interest [Line Items]
Number of service categories | service_category	500
Number of service professionals (over) | service_professional	250
Number of projects (more than) | project	25
Number of operating segments | operating_segment	2
Revenue from contracts with customers	$ 343,650,000	$ 303,443,000
Current deferred revenue	57,869,000			$ 58,220,000
Noncurrent deferred revenue	200,000			200,000
Deferred revenue recognized during period	37,100,000	36,400,000
Noncurrent capitalized sales commissions	43,200,000			39,100,000
Revenue reserve	1,800,000			1,200,000
Allowance for doubtful accounts and revenue reserve	22,421,000			20,293,000
Stockholders' equity	$ 1,291,010,000	$ 1,331,901,000		$ 1,323,552,000	$ 1,321,987,000
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment
Noncontrolling Interest [Line Items]
Stockholders' equity			$ 0
ANGI Homeservices | Class B Common Stock | IAC
Noncontrolling Interest [Line Items]
Economic interest (as a percent)	84.90%
Voting interest (as a percent)	98.30%
Difference between Revenue Guidance in Effect before and after Topic 606
Noncontrolling Interest [Line Items]
Revenue from contracts with customers	$ 15,200,000