Income Taxes - Components of deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Net operating loss	$ 7,675	$ 146,382
Mineral properties	39,555	0
Plant, equipment, and mine development	30,767	60,840
Intangible assets	21,710	0
Royalty	6,292	0
Interest expense carryforward	1,935	24,369
Asset retirement obligation	997	927
Stock-based compensation	405	257
Accrued compensation	197	0
Inventories	191	15,438
Reorganization costs	0	7,701
Other liabilities	0	609
Credits and other	0	(6)
Valuation allowance	(109,724)	(256,517)
Total net deferred tax assets	$ 0	$ 0

Deferred Tax Assets, Mineral Properties

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Deferred Tax Assets, Royalty

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible interest carryforward.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from intangible assets including goodwill.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from inventory.

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Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from property, plant, and equipment.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences from compensation and benefits, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from asset retirement obligations. An asset retirement obligation is a legal obligation associated with the disposal or retirement from service of a tangible long-lived asset.

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Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences from reserves and accruals, classified as other.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from restructuring reserve.

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Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

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Amount of deferred tax liability attributable to taxable temporary differences classified as other.

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