MINERAL PROPERTY INTERESTS AND PLANT AND EQUIPMENT (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Subtotal	$ 484,126	$ 459,006
Less: accumulated depreciation	(48,006)	(35,127)
Net carrying value	436,120	423,879
Mineral property interests
Property, Plant and Equipment [Line Items]
Subtotal	340,945	326,086
Land
Property, Plant and Equipment [Line Items]
Subtotal	8,708	8,699
Construction in process
Property, Plant and Equipment [Line Items]
Subtotal	3,901	74,643
Plant and equipment
Property, Plant and Equipment [Line Items]
Subtotal	130,572	49,578
Operating Leases
Property, Plant and Equipment [Line Items]
Subtotal	1,167
Less: accumulated depreciation	(413)
Net carrying value	754
Finance Leases
Property, Plant and Equipment [Line Items]
Subtotal	8,048
Less: accumulated depreciation	(515)
Net carrying value	7,533
Gold Bar mine | Construction in process
Interest expense
Interest Expense, Debt	$ 1,400	$ 800