INCOME TAXES - Schedule of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Net operating losses	$ 81,471	$ 5,885
Tax credit carryforwards	3,360	1,411
Intangible assets	0	82,582
Stock-based compensation	2,999	1,907
Operating lease liabilities	1,248	1,577
Fixed assets	1,315	0
Reserves and other accruals not currently deductible	20,652	9,729
Disallowed interest carryforward	15,496	718
Total deferred tax assets	126,541	103,809
Valuation allowance for deferred tax assets	(103,906)	(90,820)
Deferred tax assets	22,635	12,989
Deferred tax liabilities:
Intangible assets	(21,739)	0
Convertible debt	(459)	(12,247)
Fixed Assets	0	(109)
Operating lease right-of-use assets	(437)	(633)
Net deferred tax liability	$ 0	$ 0