OPERATING SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Segment Reporting
Gold and silver sales		$ 67,465	$ 60,388	$ 72,956
Other revenue		259
Production costs applicable to sales		(45,180)	(28,133)	(34,607)
Revision of estimates and accretion of reclamation obligations		(2,061)	(595)	(429)
Mine development costs		(3,837)	(3,866)	(1,169)
Exploration costs		(17,714)	(7,959)	(8,798)
Property holding costs		(3,879)	(3,536)	(4,336)
Impairment of mineral property interests and property and equipment		(711)		(50,600)
General and administrative expenses		(18,872)	(12,734)	(12,045)
Income (loss) on investment in Minera Santa Cruz S.A. (net of amortization)		(44)	12,951	2,414
Depreciation		3,378	1,169	942
Reclamation and Remediation		635	506
Revision of estimates and accretion of reclamation obligations		(2,061)	(595)	(429)
Impairment of mineral property interests and property and equipment		(711)		(50,600)
Impairment of investment in MSC				(11,777)
Gain on sale of assets		11	24	13
Gain on sale of marketable securities		(840)	(22)
Other-than-temporary impairment on marketable equity securities		(356)	(882)
Unrealized gain on derivative instrument		(227)	1,379
Foreign currency gain		694	581	1,906
Net loss before income and mining taxes		(26,003)	17,306	(45,010)
Revenues		67,724	60,388	72,956
Long-Lived Assets		505,265	419,744
Investment in MSC		150,064	162,320
Capital Expenditures		11,511	6,165	764
Mexico
Operating Segment Reporting
Gold and silver sales		55,845	60,388	72,956
Production costs applicable to sales		(35,292)	(28,133)	(34,607)
Revision of estimates and accretion of reclamation obligations		(326)
Mine development costs		(745)	(1,174)	(761)
Exploration costs		(5,610)	(4,100)	(4,526)
Property holding costs		(2,131)	(1,642)	(2,471)
Impairment of mineral property interests and property and equipment		(711)
General and administrative expenses		(3,772)	(2,688)	(3,953)
Segment income (loss)		7,258	22,651	26,638
Revision of estimates and accretion of reclamation obligations		(326)
Impairment of mineral property interests and property and equipment		(711)
Capital Expenditures		939	5,401	700
MSC
Operating Segment Reporting
Income (loss) on investment in Minera Santa Cruz S.A. (net of amortization)		(44)	12,951	2,414
Segment income (loss)		(44)	12,951	2,414
Los Azules
Operating Segment Reporting
Exploration costs		(7,923)	(1,649)	(1,481)
Property holding costs		(56)	(405)	(356)
General and administrative expenses		(1,242)	(646)	(647)
Segment income (loss)		(9,221)	(2,700)	(2,484)
Capital Expenditures				2
U.S.
Operating Segment Reporting
Revision of estimates and accretion of reclamation obligations		(300)
Mine development costs		(3,092)	(2,692)	(408)
Exploration costs		(2,132)	(1,973)	(2,517)
Property holding costs		(1,667)	(1,489)	(1,509)
General and administrative expenses		(1,927)	(228)	(203)
Segment income (loss)		(9,118)	(6,382)	(4,637)
Revision of estimates and accretion of reclamation obligations		(300)
Nevada
Operating Segment Reporting
Capital Expenditures		6,271	764	62
Timmins
Operating Segment Reporting
Gold and silver sales		11,620
Other revenue		259
Production costs applicable to sales		(9,888)
Revision of estimates and accretion of reclamation obligations		(1,435)
Exploration costs		(1,544)
Property holding costs		(25)
General and administrative expenses		(92)
Segment income (loss)		(1,105)
Revision of estimates and accretion of reclamation obligations		(1,435)
Total Segment
Operating Segment Reporting
Gold and silver sales		67,465	60,388	72,956
Other revenue		259
Production costs applicable to sales		(45,180)	(28,133)	(34,607)
Revision of estimates and accretion of reclamation obligations		(2,061)
Mine development costs		(3,837)	(3,866)	(1,169)
Exploration costs		(17,209)	(7,722)	(8,524)
Property holding costs		(3,879)	(3,536)	(4,336)
Impairment of mineral property interests and property and equipment		(711)
General and administrative expenses		(7,033)	(3,562)	(4,803)
Income (loss) on investment in Minera Santa Cruz S.A. (net of amortization)		(44)	12,951	2,414
Segment income (loss)		(12,230)	26,520	21,931
Revision of estimates and accretion of reclamation obligations		(2,061)
Impairment of mineral property interests and property and equipment		(711)
Capital Expenditures		11,511	6,165	764
Corporate & Other
Operating Segment Reporting
Revision of estimates and accretion of reclamation obligations			(595)	(429)
Exploration costs		(505)	(237)	(274)
Impairment of mineral property interests and property and equipment				(50,600)
General and administrative expenses		(11,839)	(9,172)	(7,242)
Depreciation		(1,453)	(1,169)	(942)
Revision of estimates and accretion of reclamation obligations			(595)	(429)
Impairment of mineral property interests and property and equipment				(50,600)
Impairment of investment in MSC				(11,777)
Interest income and other income		(938)	835	2,404
Gain on sale of assets		11	24	13
Gain on sale of marketable securities		840	22
Other-than-temporary impairment on marketable equity securities		(356)	(882)
Unrealized gain on derivative instrument		(227)	1,379
Foreign currency gain		694	581	1,906
Net loss before income and mining taxes		(26,003)	17,306	(45,010)
Bank of Nova Scotia | Sales | Customer
Operating Segment Reporting
Gold and silver sales		$ 65,900	$ 58,100	$ 67,200
Gold and silver sales, percentage		94.00%	96.00%	92.00%
MSC
Operating Segment Reporting
Impairment of mineral property interests and property and equipment		$ 0	$ 0	$ (11,800)
Income (loss) on investment in Minera Santa Cruz S.A. (net of amortization)		(44)	12,951	2,414
Impairment of mineral property interests and property and equipment		0	0	(11,800)
Investment in MSC	$ 167,107	150,064	162,320	167,107
Los Azules Copper Project
Operating Segment Reporting
Impairment of mineral property interests and property and equipment	(11,400)
Impairment of mineral property interests and property and equipment	$ (11,400)
Capital Expenditures		4,301
Los Azules Copper Project | Argentina
Operating Segment Reporting
Impairment of mineral property interests and property and equipment				(11,399)
Impairment of mineral property interests and property and equipment				(11,399)
Canada
Operating Segment Reporting
Revenues		11,879
Long-Lived Assets		85,179	663
Mexico
Operating Segment Reporting
Revenues		55,845	60,388	$ 72,956
Long-Lived Assets		35,446	27,582
United States
Operating Segment Reporting
Long-Lived Assets		43,086	37,620
Argentina
Operating Segment Reporting
Long-Lived Assets		$ 341,554	$ 353,879