OPERATING SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Operating Segment Reporting
Revenues	$ 34,179	$ 15,110	$ 75,464	$ 29,943
Cost of goods and services sold	(9,923)	(6,550)	(24,814)	(14,399)
Revision of estimates and accretion of reclamation obligations	(288)	(116)	(582)	(221)
Property holding costs	(189)	(423)	(1,600)	(1,611)
General and administrative expenses	(5,814)	(4,078)	(11,001)	(8,371)
(Loss) from investment in Minera Santa Cruz S.A. (net of amortization)	(2,265)	(263)	(2,477)	(73)
Depreciation			(4,564)	(809)
Interest and other expense	354	(109)	220	(175)
Revision of estimates and accretion of reclamation obligations	(288)	(116)	(582)	(221)
Gain on sale of assets	(99)		(99)	11
Gain (loss) on sale of marketable equity securities (note 2)	(33)	840	(767)	840
Unrealized (loss) gain on derivative instrument	(1)	(722)	(865)	1,069
(Gain) on disposal of fixed assets			(99)	11
Foreign currency gain	1,482	1,050	2,409	1,075
Net loss before income and mining taxes	(7,520)	(1,559)	(13,869)	(7,231)
Long-Lived Assets	526,790		526,790		$ 505,265
Investment in MSC	140,356		140,356		150,064
Mexico
Operating Segment Reporting
Property holding costs	(41)	(63)	(1,190)	(1,045)
General and administrative expenses	(800)	(1,040)	(1,629)	(1,879)
Segment income (loss)	3,680	3,757	12,160	8,091
MSC
Operating Segment Reporting
(Loss) from investment in Minera Santa Cruz S.A. (net of amortization)	(2,265)	(263)	(2,477)	(73)
Segment income (loss)	(2,265)	(263)	(2,477)	(73)
Los Azules
Operating Segment Reporting
Property holding costs		(47)	(40)	(48)
General and administrative expenses	(470)	(421)	(748)	(629)
Segment income (loss)	(2,341)	(1,309)	(5,866)	(7,819)
U.S.
Operating Segment Reporting
Property holding costs	(96)	(313)	(275)	(518)
General and administrative expenses	(1,495)	(359)	(2,358)	(785)
Segment income (loss)	(2,742)	(1,662)	(5,784)	(3,737)
Canada
Operating Segment Reporting
Property holding costs	(52)		(95)
General and administrative expenses	(52)	(26)	(140)	(26)
Segment income (loss)	(1,497)	(156)	(3,822)	(156)
Total Segment
Operating Segment Reporting
Property holding costs	(189)	(423)	(1,600)	(1,611)
General and administrative expenses	(2,817)	(1,846)	(4,875)	(3,319)
(Loss) from investment in Minera Santa Cruz S.A. (net of amortization)	(2,265)	(263)	(2,477)	(73)
Segment income (loss)	(5,165)	367	(5,789)	(3,694)
Corporate & Other
Operating Segment Reporting
Revision of estimates and accretion of reclamation obligations	(288)	(116)	(582)	(221)
Other exploration costs		(155)		(275)
General and administrative expenses	(2,997)	(2,232)	(6,126)	(5,052)
Depreciation	(273)	(482)	(633)	(809)
Interest and other expense	354	(109)	220
Revision of estimates and accretion of reclamation obligations	(288)	(116)	(582)	(221)
Interest income and other income				(175)
Gain on sale of assets	(99)		(99)	11
Gain (loss) on sale of marketable equity securities (note 2)	(33)	840	(767)	840
Unrealized fair value loss on marketable equity securities	(500)		(1,637)
Unrealized (loss) gain on derivative instrument	(1)	(722)	(865)	1,069
Foreign currency gain	1,482	1,050	2,409	1,075
MSC
Operating Segment Reporting
(Loss) from investment in Minera Santa Cruz S.A. (net of amortization)	(2,265)	(263)	(2,477)	(73)
Investment in MSC	140,356		140,356		150,064	$ 162,320
Canada
Operating Segment Reporting
Revenues	19,798		35,666
Long-Lived Assets	87,051		87,051		85,179
Mexico
Operating Segment Reporting
Revenues	14,381	15,110	39,798	29,943
Long-Lived Assets	32,515		32,515		35,446
United States
Operating Segment Reporting
Long-Lived Assets	75,378		75,378		43,086
United States | Gold Bar Complex
Operating Segment Reporting
Mine Construction Costs	18,200		27,000
Construction-in-progress					33,000
Argentina
Operating Segment Reporting
Long-Lived Assets	331,846		331,846		$ 341,554
Gold and silver sales
Operating Segment Reporting
Revenues	33,806	15,110	74,847	29,943
Gold and silver sales | Mexico
Operating Segment Reporting
Revenues	14,381	15,110	39,798	29,943
Gold and silver sales | Canada
Operating Segment Reporting
Revenues	19,425		35,049
Gold and silver sales | Total Segment
Operating Segment Reporting
Revenues	33,806	15,110	74,847	29,943
Other revenue
Operating Segment Reporting
Revenues	373		617
Other revenue | Canada
Operating Segment Reporting
Revenues	373		617
Other revenue | Total Segment
Operating Segment Reporting
Revenues			617
Production costs applicable to sales
Operating Segment Reporting
Cost of goods and services sold	(24,256)	(8,560)	(50,650)	(15,544)
Production costs applicable to sales | Mexico
Operating Segment Reporting
Cost of goods and services sold	(8,821)	(8,560)	(22,429)	(15,544)
Production costs applicable to sales | Canada
Operating Segment Reporting
Cost of goods and services sold	(15,435)		(28,221)
Production costs applicable to sales | Total Segment
Operating Segment Reporting
Cost of goods and services sold	(24,256)	(8,560)	(50,650)	(15,544)
Mine development costs
Operating Segment Reporting
Cost of goods and services sold	(710)	(720)	(1,090)	(1,835)
Mine development costs | Mexico
Operating Segment Reporting
Cost of goods and services sold	(710)	(177)	(1,090)	(332)
Mine development costs | U.S.
Operating Segment Reporting
Cost of goods and services sold		(543)		(1,503)
Mine development costs | Total Segment
Operating Segment Reporting
Cost of goods and services sold	(710)	(720)	(1,090)	(1,835)
Exploration costs
Operating Segment Reporting
Cost of goods and services sold	(9,107)	(3,086)	(20,561)	(11,530)
Exploration costs | Mexico
Operating Segment Reporting
Cost of goods and services sold	(329)	(1,513)	(1,300)	(3,052)
Exploration costs | Los Azules
Operating Segment Reporting
Cost of goods and services sold	(1,871)	(841)	(5,078)	(7,142)
Exploration costs | U.S.
Operating Segment Reporting
Cost of goods and services sold	(1,151)	(447)	(3,151)	(931)
Exploration costs | Canada
Operating Segment Reporting
Cost of goods and services sold	(5,756)	(130)	(11,032)	(130)
Exploration costs | Total Segment
Operating Segment Reporting
Cost of goods and services sold	$ (9,107)	$ (2,931)	$ (20,561)	$ (11,255)