INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Assets and Liabilities Associated with MSC (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	$ 108,450	$ 78,574
Total assets	571,037	498,318
Current liabilities	25,771	20,581
Total liabilities	59,786	$ 55,279
MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	99,100
Total assets	419,100
Current liabilities	35,000
Total liabilities	103,700
MSC | Current Period Values Excluding Fair Value Increments And Impairment Charge
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Current assets	98,500
Total assets	255,300
Current liabilities	40,200
Total liabilities	$ 65,600