NET LOSS PER SHARE - Reconciliation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
NET LOSS PER SHARE
Net loss					$ (23,542)	$ (9,778)	$ (19,814)	$ (99,191)	$ (56,712)	$ (152,325)	$ (59,747)
Weighted average common shares outstanding:									454,899	403,457	361,845
Diluted shares outstanding:									454,899	403,457	361,845
Net loss per share:
Basic and Diluted (in dollars per share)	$ (0.05)	$ (0.04)	$ (0.01)	$ (0.03)	$ (0.06)	$ (0.02)	$ (0.05)	$ (0.25)	$ (0.12)	$ (0.38)	$ (0.17)