SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Summary of Income (Loss) per Basic and Diluted Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounting Policies [Abstract]
Net loss, adjusted for change in fair value of warrant liabilities for diluted earnings per share	$ (12,342)	$ (47,547)	$ (57,605)	$ (216,602)
Weighted average shares outstanding – Basic	90,852	84,968	89,559	70,737
Weighted average shares outstanding – Diluted	90,852	84,968	89,559	70,737
Income loss per share:
Basic	$ (0.14)	$ (0.56)	$ (0.64)	$ (3.06)
Diluted	$ (0.14)	$ (0.56)	$ (0.64)	$ (3.06)