SEGMENT INFORMATION - Segmented Revenue Disaggregated by Service (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenue from contracts with customers	$ 389,913	$ 357,358	$ 1,108,624	$ 1,004,697
North America
Segment Reporting Information [Line Items]
Revenue from contracts with customers	372,226	339,144	1,053,775	945,538
North America | Marketplace revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	306,707	273,462	858,656	755,253
North America | Consumer connection revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	287,568	252,552	800,047	695,370
North America | Service professional membership subscription revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	12,195	15,995	38,989	48,697
North America | Other revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	6,944	4,915	19,620	11,186
North America | Advertising and other revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	65,519	65,682	195,119	190,285
Europe
Segment Reporting Information [Line Items]
Revenue from contracts with customers	17,687	18,214	54,849	59,159
Europe | Advertising and other revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	403	624	1,417	1,859
Europe | Consumer connection revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	14,006	14,125	43,640	46,480
Europe | Service professional membership subscription revenue
Segment Reporting Information [Line Items]
Revenue from contracts with customers	$ 3,278	$ 3,465	$ 9,792	$ 10,820