Derivative Financial Instruments - Narrative (Details) $ in Thousands	3 Months Ended	8 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($) oz	Aug. 31, 2020 oz	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Derivative [Line Items]
Production to be sold, percent						50.00%
Fixed Interest Rate Swap One
Derivative [Line Items]
Derivative, Notional Amount	$ 50,000		$ 50,000
Concentrate Sales Contracts
Derivative [Line Items]
Provisional gain (loss) on derivatives and commodity contracts			337	$ 111	$ 631
Zinc options
Derivative [Line Items]
Net derivative gain (loss)			0	753	0
Interest rate swap
Derivative [Line Items]
Net derivative gain (loss)			(178)	$ (60)	$ 0
Fixed Interest Rate Swap Two
Derivative [Line Items]
Derivative, Notional Amount	$ 75,000		75,000
Designated as Hedging Instrument | Gold zero cost collars
Derivative [Line Items]
Ounces of gold per month (in ounces) | oz	21,000
After tax gains in AOCI			$ 500
Designated as Hedging Instrument | Gold zero cost collars | Forecast
Derivative [Line Items]
Ounces of gold per month (in ounces) | oz		12,000