Fair Value Accounting (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Accounting
Other investments	$ 3,511	$ 5,462
Fair Value Transfers Between Levels	0
Midas Gold Shares [Member]
Fair Value Accounting
Other investments	3,511	5,462
Recurring \| Midas Gold Shares [Member]
Fair Value Accounting
Other investments	3,511	5,462
Recurring \| Fair Value, Inputs, Level 1 [Member] \| Midas Gold Shares [Member]
Fair Value Accounting
Other investments	$ 3,511	5,462
Non-recurring \| Used mill equipment, Canada
Fair Value Accounting
Used mill equipment (non-recurring)		5,500
Non-recurring \| Fair Value, Inputs, Level 3 [Member] \| Used mill equipment, Canada
Fair Value Accounting
Used mill equipment (non-recurring)		$ 5,500

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- Definition

Amount of transfers of financial instruments classified measured on a recurring basis between the fair value hierarchy level 1, level 2 and level 3.

+ References

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