SEGMENT INFORMATION - Revenue Disaggregated by Service (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenue	$ 321,508	$ 357,358	$ 343,896	$ 303,443	$ 278,992	$ 303,116	$ 294,822	$ 255,311	$ 1,326,205	$ 1,132,241	$ 736,386
Felix
Segment Reporting Information [Line Items]
Revenue										36,900	26,900
North America
Segment Reporting Information [Line Items]
Revenue									1,249,892	1,062,171	678,897
Europe
Segment Reporting Information [Line Items]
Revenue									76,313	70,070	57,489
Consumer connection revenue | North America
Segment Reporting Information [Line Items]
Revenue									913,533	704,341	521,481
Consumer connection revenue | Europe
Segment Reporting Information [Line Items]
Revenue									59,611	50,913	40,009
Service professional membership subscription revenue | North America
Segment Reporting Information [Line Items]
Revenue									64,706	66,214	56,135
Service professional membership subscription revenue | Europe
Segment Reporting Information [Line Items]
Revenue									14,231	17,362	16,596
Other revenue | North America
Segment Reporting Information [Line Items]
Revenue									6,971	3,940	3,798
Total Marketplace revenue | North America
Segment Reporting Information [Line Items]
Revenue									985,210	774,495	581,414
Advertising and other revenue | North America
Segment Reporting Information [Line Items]
Revenue									264,682	287,676	97,483
Advertising and other revenue | Europe
Segment Reporting Information [Line Items]
Revenue									$ 2,471	$ 1,795	$ 884