INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Assets and Liabilities Associated with MSC (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	$ 66,074	$ 78,574
Total assets	531,272	498,318
Current liabilities	19,077	20,581
Total liabilities	52,727	$ 55,279
MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	101,400
Total assets	430,100
Current liabilities	37,100
Total liabilities	109,100
MSC | Current Period Values Excluding Fair Value Increments And Impairment Charge
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	100,700
Total assets	261,300
Current liabilities	47,100
Total liabilities	$ 72,500