Derivative Financial Instruments - Summary of Pre-tax Gains (Losses) On Derivatives Designated as Cash Flow Hedges (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	$ (12,434)	$ (136)	$ 0
Gains (losses) reclassified from AOCI into net income - effective portion:	1,434	0	0
Gold zero cost collars
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	(32,345)	(136)	0
Gains (losses) reclassified from AOCI into net income - effective portion:	7,598	0	0
Foreign Exchange Forward
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	19,911	0	0
Gains (losses) reclassified from AOCI into net income - effective portion:	$ (6,164)	$ 0	$ 0