Financial Instruments - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) oz	Dec. 31, 2019 USD ($)
Silver, Ounces, Copper Contracts | Commodity contracts | Designated as Hedging Instrument
Derivatives, Fair Value [Line Items]
Amount | oz	41,414
WebBank
Derivatives, Fair Value [Line Items]
Undisbursed loan commitment | $	$ 90,980	$ 125,861
Minimum
Derivatives, Fair Value [Line Items]
Derivative, remaining maturity	3 years
Maximum
Derivatives, Fair Value [Line Items]
Derivative, remaining maturity	5 years