INCOME AND MINING TAXES - Tax Effects of Temporary Differences (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Net operating loss carryforward	$ 57,983	$ 65,174
Mineral properties	52,471	69,326
Other temporary differences	21,857	22,433
Total gross deferred tax assets	132,311	156,933
Less: valuation allowance	(130,002)	(149,342)	$ (149,921)	$ (154,298)
Net deferred tax liabilities (assets)	2,309	7,591
Deferred tax liabilities:
Acquired mineral property interests	(2,895)	(7,746)
Other temporary differences	(39,986)
Total deferred tax liabilities	(42,881)	(7,746)
Total net deferred tax liability	$ (40,572)	$ (155)