Note 6 - Income Taxes - Changes in the Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance at beginning of year	$ (94,981)	$ (78,684)	$ (99,602)	$ (115,806)
Increase Due to Uncertainty of Recovery [Member]
Valuation allowance, deferred tax asset, increase (decrease)	(5,700)	(14,964)	(2,868)
Decrease Related to Utilization and Expiration [Member]
Valuation allowance, deferred tax asset, increase (decrease)	873	35,882	19,072
Klondex Mines Ltd [Member]
Valuation allowance on deferred tax assets acquired with the Klondex acquisition	$ (11,470)

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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The amount of the valuation allowance recorded in a business combination against deductible temporary differences for which related tax benefits will be recorded as a reduction of the acquired entity's income tax expense (after such benefits are first being applied to reduce goodwill and then other noncurrent intangible assets to zero).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 740
-Section 25
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109126419&loc=d3e9901-128506

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- Definition

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
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