OPERATING SEGMENT REPORTING - Summary of Reportable Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Segment Reporting
Revenue from gold and silver sales									$ 136,541	$ 104,789	$ 117,019
Depreciation and depletion									(23,798)	(22,910)	(24,753)
Gross profit (loss)	$ (5,897)	$ 344	$ 4,059	$ (4,986)	$ (13,687)	$ (701)	$ (8,875)	$ (3,685)	(6,480)	(26,948)	8,986
Advanced projects									(12,439)	(11,681)	(9,520)
Impairment loss on mineral property interests and plant and equipment (Note 8)									0	(83,805)
Loss from investment in Minera Santa Cruz S.A.									(7,533)	(1,517)	(8,754)
Other operating										(1,968)
Loss before income and mining taxes									(64,199)	(153,715)	(63,591)
Capital expenditures									36,033	13,925	30,270
United States Reportable Segment [Member]
Operating Segment Reporting
Depreciation and depletion									(8,502)	(11,785)	(10,934)
Gross profit (loss)									(3,288)	(21,366)	(701)
Advanced projects									(440)	(1,071)	(649)
Impairment loss on mineral property interests and plant and equipment (Note 8)										(83,805)
Other operating										(1,390)
Segment loss									(9,603)	(114,409)	(9,904)
Capital expenditures									2,416	4,821	18,806
Canada
Operating Segment Reporting
Depreciation and depletion									(15,296)	(10,883)	(13,271)
Gross profit (loss)									2,447	(4,070)	5,666
Advanced projects									(2,635)	(6,088)	(1,636)
Other operating										(578)
Segment loss									(15,205)	(17,186)	(21,749)
Capital expenditures									33,617	9,104	11,464
Mexico Reportable Segment [Member]
Operating Segment Reporting
Depreciation and depletion										(242)	(548)
Gross profit (loss)									(5,640)	(1,512)	4,021
Advanced projects									(4,345)	(4,522)	(7,235)
Segment loss									(9,999)	(6,547)	(3,214)
MSC
Operating Segment Reporting
Loss from investment in Minera Santa Cruz S.A.									(7,533)	(1,517)	(8,754)
Segment loss									(7,533)	(1,517)	(8,754)
Los Azules
Operating Segment Reporting
Advanced projects									(5,019)
Segment loss									(6,717)	(2,121)	(3,411)
Total Segment
Operating Segment Reporting
Depreciation and depletion									(23,798)	(22,910)	(24,753)
Gross profit (loss)									(6,481)	(26,948)	8,986
Advanced projects									(12,439)	(11,681)	(9,520)
Impairment loss on mineral property interests and plant and equipment (Note 8)										(83,805)
Loss from investment in Minera Santa Cruz S.A.									(7,533)	(1,517)	(8,754)
Other operating										(1,968)
Segment loss									(49,056)	(141,780)	(47,032)
General and Administrative and other									(15,143)	(11,935)	(16,559)
Gold and silver sales
Operating Segment Reporting
Revenue from gold and silver sales	$ 34,966	$ 37,129	$ 40,706	$ 23,740	$ 27,703	$ 27,395	$ 18,291	$ 31,400	136,541	104,789	117,019
Gold and silver sales | United States Reportable Segment [Member]
Operating Segment Reporting
Revenue from gold and silver sales									79,205	48,884	43,847
Gold and silver sales | Canada
Operating Segment Reporting
Revenue from gold and silver sales									50,704	41,452	50,058
Gold and silver sales | Mexico Reportable Segment [Member]
Operating Segment Reporting
Revenue from gold and silver sales									6,632	14,453	23,114
Gold and silver sales | Total Segment
Operating Segment Reporting
Revenue from gold and silver sales									136,541	104,789	117,019
Product [Member]
Operating Segment Reporting
Production costs applicable to sales									(119,223)	(108,827)	(83,280)
Product [Member] | United States Reportable Segment [Member]
Operating Segment Reporting
Production costs applicable to sales									(73,991)	(58,465)	(33,614)
Product [Member] | Canada
Operating Segment Reporting
Production costs applicable to sales									(32,961)	(34,639)	(31,121)
Product [Member] | Mexico Reportable Segment [Member]
Operating Segment Reporting
Production costs applicable to sales									(12,272)	(15,723)	(18,545)
Product [Member] | Total Segment
Operating Segment Reporting
Production costs applicable to sales									(119,224)	(108,827)	(83,280)
Exploration | United States Reportable Segment [Member]
Operating Segment Reporting
Production costs applicable to sales									(5,875)	(6,777)	(8,554)
Exploration | Canada
Operating Segment Reporting
Production costs applicable to sales									(15,017)	(6,450)	(25,779)
Exploration | Mexico Reportable Segment [Member]
Operating Segment Reporting
Production costs applicable to sales									(14)	(513)
Exploration | Los Azules
Operating Segment Reporting
Production costs applicable to sales									(1,698)	(2,121)	(3,411)
Exploration | Total Segment
Operating Segment Reporting
Production costs applicable to sales									$ (22,604)	$ (15,861)	$ (37,744)