THE COMPANY AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) service_professional in Thousands, project in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) project service_professional	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) project service_professional operating_segment service_category	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Noncontrolling Interest [Line Items]
Number of service categories | service_category			500
Number of service professionals (over) | service_professional	230		230
Number of projects (more than) | project	25		25
Number of operating segments | operating_segment			2
Revenue from contracts with customers	$ 389,913,000	$ 357,358,000	$ 1,108,624,000	$ 1,004,697,000
Current deferred revenue	58,169,000		58,169,000			$ 58,220,000
Noncurrent deferred revenue	100,000		100,000			200,000
Deferred revenue recognized during period			55,700,000	58,500,000
Capitalized sales commissions where the customer relationship period is greater than one year	52,200,000		52,200,000			39,100,000
Current capitalized sales commissions	50,000,000.0		50,000,000.0			35,100,000
Non-current capitalized sales commissions	2,200,000		2,200,000			4,000,000.0
Revenue reserve	2,000,000.0		2,000,000.0			1,200,000
Allowance for doubtful accounts and revenue reserve	29,787,000		29,787,000			20,293,000
Stockholders' equity	$ 1,283,761,000	1,332,451,000	$ 1,283,761,000	1,332,451,000	$ 1,301,926,000	1,323,552,000	$ 1,344,546,000	$ 1,321,987,000
Accounting Standards Update			us-gaap:AccountingStandardsUpdate201613Member
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)	84.50%		84.50%
Voting interest (as a percent)	98.20%		98.20%
Difference between Revenue Guidance in Effect before and after Topic 606
Noncontrolling Interest [Line Items]
Revenue from contracts with customers	$ 20,800,000		$ 51,300,000
United States
Noncontrolling Interest [Line Items]
Revenue from contracts with customers	$ 368,082,000	$ 335,230,000	$ 1,041,903,000	$ 934,409,000
Revenue | Geographic Concentration Risk | United States
Noncontrolling Interest [Line Items]
Concentration risk (as a percent)	94.00%		94.00%