TRANSACTION AND INTEGRATION RELATED COSTS IN CONNECTION WITH THE COMBINATION - Summary (Details) - USD ($) $ in Thousands		12 Months Ended
	Sep. 29, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition
Stock-based compensation expense		$ 97,078	$ 149,230	$ 8,916
Cost of revenue
Business Acquisition
Stock-based compensation expense			19
Selling and marketing expense
Business Acquisition
Stock-based compensation expense		3,368	25,763	863
General and administrative expense
Business Acquisition
Stock-based compensation expense		84,028	107,662	6,804
Product development expense
Business Acquisition
Stock-based compensation expense		9,682	15,786	1,249
Angie's List
Business Acquisition
Transaction and integration related costs		3,584	44,101
Stock-based compensation expense		70,645	122,066
Total		74,229	166,167
Accrual for Business Combination [Roll Forward]
Accrual as of January 1		8,480	0
Costs incurred		3,584	44,101
Payments made	$ (1,900)	(12,064)	(35,621)
Accrual as of December 31		0	8,480	$ 0
Angie's List | Cost of revenue
Business Acquisition
Transaction and integration related costs		0	0
Stock-based compensation expense		0	0
Total		0	0
Angie's List | Selling and marketing expense
Business Acquisition
Transaction and integration related costs		0	7,430
Stock-based compensation expense		2,161	24,416
Total		2,161	31,846
Angie's List | General and administrative expense
Business Acquisition
Transaction and integration related costs		3,584	36,120
Stock-based compensation expense		61,010	83,420
Total		64,594	119,540
Angie's List | Product development expense
Business Acquisition
Transaction and integration related costs		0	551
Stock-based compensation expense		7,474	14,230
Total		$ 7,474	$ 14,781