Derivative Financial Instruments - Summary of Pre-tax Gains (Losses) On Derivatives Designated as Cash Flow Hedges (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	$ (21,248)	$ 0	$ (28,139)	$ 0
Gains (losses) reclassified from AOCI into net income - effective portion:	2,642	0	1,963	0
Gold zero cost collars
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	(24,003)	0	(38,353)	0
Gains (losses) reclassified from AOCI into net income - effective portion:	4,563	0	4,563	0
Foreign Exchange Forward
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gains (losses) recognized in OCI - effective portion:	2,755	0	10,214	0
Gains (losses) reclassified from AOCI into net income - effective portion:	$ (1,921)	$ 0	$ (2,600)	$ 0