Income taxes (Schedule of Deferred Tax Assets and (Liabilities)) (Details) - USD ($) |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|---|
| Deferred tax assets (liabilities): | |||
| Net operating loss carryforwards | $ 30,745,000 | $ 25,837,000 | |
| Research and development credit carryforwards | 989,000 | 989,000 | |
| Stock option expense | 1,384,000 | 252,000 | |
| Impairment of mining related assets and other | 8,779,000 | 14,000 | |
| Total deferred tax assets | 41,897,000 | 27,092,000 | |
| Valuation allowance | (41,897,000) | (27,092,000) | |
| Net deferred tax assets | |||
| Deferred income tax liabilities: | |||
| Indefinite life intangible assets | (142,709) | (699,000) | |
| Net deferred tax liabilities | $ (142,709) | $ (699,000) |
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- References No definition available.
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, before allocation of valuation allowance, of deferred tax asset attributable to deductible temporary differences, classified as other. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible research tax credit carryforwards. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount before allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences from share-based compensation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount, after deferred tax asset, of deferred tax liability attributable to taxable differences without jurisdictional netting. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition Amount of deferred tax liability attributable to taxable temporary differences from intangible assets other than goodwill. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- References No definition available.
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