INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Assets and Liabilities Associated with MSC (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	$ 92,127	$ 53,497
Total assets	539,776	499,936
Current liabilities	(46,312)	(45,554)
Total liabilities	(128,911)	$ (134,608)
Balance excluding FV increments | Minera Santa Cruz S.A. [Member]
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	83,723
Total assets	177,357
Current liabilities	(44,463)
Total liabilities	(74,576)
Adjustments | Minera Santa Cruz S.A. [Member]
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	435
Total assets	95,607
Total liabilities	(3,117)
Balance including FV increments | Minera Santa Cruz S.A. [Member]
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	84,158
Total assets	272,964
Current liabilities	(44,463)
Total liabilities	$ (77,693)