Derivative Financial Instruments - Summary of Derivative Cash Flow Hedges (Details) - Designated as Hedging Instrument	12 Months Ended
	Dec. 31, 2019 oz $ / oz
Gold Put Options - 2020
Derivative [Line Items]
Average gold strike price per ounce | $ / oz	1,408
Notional ounces | oz	96,000
Gold Call Options - 2020
Derivative [Line Items]
Average gold strike price per ounce | $ / oz	1,803
Notional ounces | oz	96,000