INTANGIBLE ASSETS AND GOODWILL - Gross Carrying Amount and Accumulated Amortization of Finite-lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 507,875	$ 44,684
Accumulated Amortization	(49,869)	(35,244)
Net Carrying Amount	$ 458,006	9,440
Developed technology
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	2 years 10 months 24 days
Gross Carrying Amount	$ 141,337	39,984
Accumulated Amortization	(22,144)	(34,268)
Net Carrying Amount	$ 119,193	5,716
Content library
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	3 years 7 months 6 days
Gross Carrying Amount	$ 4,700	4,700
Accumulated Amortization	(1,619)	(976)
Net Carrying Amount	$ 3,081	3,724
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	10 years 6 months
Gross Carrying Amount	$ 296,046	0
Accumulated Amortization	(12,125)	0
Net Carrying Amount	$ 283,921	0
Customer contracts
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	1 year 6 months
Gross Carrying Amount	$ 58,580	0
Accumulated Amortization	(12,921)	0
Net Carrying Amount	$ 45,659	0
Trade names, trademarks, and domain names
Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	2 years 6 months
Gross Carrying Amount	$ 7,212	0
Accumulated Amortization	(1,060)	0
Net Carrying Amount	$ 6,152	$ 0