Derivative Financial Instruments - Summary of Provisionally Priced Sales (Details) - Gold concentrates sales agreements $ in Thousands	Jun. 30, 2020 USD ($) oz $ / oz
2018
Derivative instruments Settlement
Derivative average price | $ / oz	1,728
Notional Amount Derivative | $	$ 26,173
Outstanding Provisionally Priced Sales Consists of Gold | oz	15,147
Thereafter
Derivative instruments Settlement
Derivative average price | $ / oz	0
Notional Amount Derivative | $	$ 0
Outstanding Provisionally Priced Sales Consists of Gold | oz	0