Income and Mining Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Contingency [Line Items]
Tax (expense) benefit	$ 6,400	$ 13,113	$ 34,526	$ 12,018
Effective Income Tax Rate Reconciliation, Percent	(13.20%)
Unrecognized Tax Benefits	$ 300		300		$ 700
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	400		400		$ 1,100
Minimum
Income Tax Contingency [Line Items]
Unrecognized income tax liability	500		500
Maximum
Income Tax Contingency [Line Items]
Unrecognized income tax liability	$ 1,500		$ 1,500