Derivative Financial Instruments - Summary of Classification of Fair Value of Derivative Instruments (Details) - Silver and Gold Concentrate Sales Agreements - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Prepaid expenses and other
Fair value of the derivative instruments
Fair value of derivative asset	$ 481	$ 753
Accrued liabilities and other
Fair value of the derivative instruments
Fair value of derivative liability	$ 67	$ 275

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Period Type:	instant