Derivative Financial Instruments - Summary of Provisionally Priced Sales (Details) $ in Thousands	Mar. 31, 2018 USD ($) oz $ / oz
Silver concentrate sales agreements | 2018
Derivative instruments Settlement
Derivative, notional amount | $	$ (831)
Derivative average price	16.66
Outstanding Provisionally Priced Sales Consists of Silver | oz	49,853
Silver concentrate sales agreements | Thereafter
Derivative instruments Settlement
Derivative, notional amount | $	$ 0
Derivative average price	0.00
Outstanding Provisionally Priced Sales Consists of Silver | oz	0
Gold concentrates sales agreements | 2018
Derivative instruments Settlement
Derivative, notional amount | $	$ (59,332)
Derivative average price	1,317.00
Outstanding Provisionally Priced Sales Consists of Gold | oz	45,051
Gold concentrates sales agreements | Thereafter
Derivative instruments Settlement
Derivative, notional amount | $	$ 0
Derivative average price	0.00
Outstanding Provisionally Priced Sales Consists of Gold | oz	0
Zinc Put Options, Purchased [Member]
Derivative instruments Settlement
Derivative average price	3,000.00
Zinc Put Options, Purchased [Member] | 2018
Derivative instruments Settlement
Derivative, notional amount | $	$ (8,100)
Derivative, Nonmonetary Notional Amount | oz	2,700
Derivative average price	3,000.00
Zinc Put Options, Purchased [Member] | Thereafter
Derivative instruments Settlement
Derivative, notional amount | $	$ 0
Derivative, Nonmonetary Notional Amount | oz	0
Derivative average price	0.00
Zinc Call Options, Sold [Member] | 2018
Derivative instruments Settlement
Derivative, notional amount | $	$ (10,935)
Derivative, Nonmonetary Notional Amount | oz	2,700
Derivative average price	4,050.00
Zinc Call Options, Sold [Member] | Thereafter
Derivative instruments Settlement
Derivative, notional amount | $	$ 0
Derivative, Nonmonetary Notional Amount | oz	0
Derivative average price	0.00