PLANT AND EQUIPMENT, MINE DEVELOPMENT AND CONSTRUCTION IN PROGRESS - Construction-in-progress (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Construction in progress
Construction-in-progress	$ 8,178	$ 2,812
Gold Bar project
Construction in progress
Construction-in-progress	6,011
Black Fox
Construction in progress
Construction-in-progress	67
El Gallo 2 project
Construction in progress
Construction-in-progress	$ 2,100	$ 2,812

Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Name:	us-gaap_ConstructionInProgressGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant