LIQUIDITY (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Cash balances	$ 117,861	$ 877	$ 50,315
Proceeds from issuance of common stock	$ 72,203	$ 2,471
Retired Liquidity Elements [Abstract]
Registered share available for future sales	0
Cantor | Controlled Equity Offering Sales Agreement
Number of common stock issued	9,300,000
Proceeds from issuance of common stock	$ 47,300
Lincoln Park | December 2020 PA
Number of common stock issued	3,800,000
Percentage of outstanding shares of common stock	19.90%
Proceeds from issuance of common stock	$ 24,900
enCore
Elimination of bonding liability			9,300
Elimination of asset retirement obligations			5,200
Annual expenditures related to reclamation and compliance costs			4,000
Common stock received and royalty interest retained			$ 1,800