INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Assets and Liabilities Associated with MSC (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	$ 81,012	$ 53,497
Total assets	528,180	499,936
Current liabilities	(45,733)	(45,554)
Total liabilities	(134,431)	$ (134,608)
Balance excluding FV increments | MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	86,274
Total assets	176,082
Current liabilities	(39,203)
Total liabilities	(68,461)
Adjustments | MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	488
Total assets	105,603
Total liabilities	(3,502)
Balance including FV increments | MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	86,762
Total assets	281,685
Current liabilities	(39,203)
Total liabilities	$ (71,963)