INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Summary of Operating Results from MSC (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Revenue from gold and silver sales									$ 117,019	$ 128,175	$ 67,465
Gross Profit	$ 1,261	$ 1,619	$ 4,677	$ 1,429	$ 2,749	$ 6,013	$ 9,092	$ 14,228	8,986	32,082	20,080
Net income (loss) before tax									(63,591)	(47,640)	(26,003)
Net loss	$ (25,132)	$ (11,465)	$ (13,014)	$ (10,136)	$ (20,989)	$ (13,290)	$ (5,380)	$ (5,211)	(59,747)	(44,870)	(10,634)
Income and mining tax recovery (note 19)									$ (3,844)	(2,770)	(15,369)
Subsidiary (as a percent)									100.00%
Ownership interest (as a percent)	49.00%								49.00%
(Loss) from investment in MSC, net of amortization									$ (8,754)	(11,865)	(44)
MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Revenue from gold and silver sales									263,887	213,096	235,650
Production costs applicable to sales									(159,915)	(151,779)	(156,347)
Depreciation and depletion									(69,995)	(52,200)	(48,278)
Gross Profit									(33,977)	(9,117)	(31,025)
Exploration									(10,635)	(5,884)	(5,198)
Other expenses									(13,065)	(12,840)	(12,527)
Net income (loss) before tax									10,277	(9,607)	13,300
Current and deferred tax expense									(14,556)	(10,934)	(18,050)
Net loss									(4,279)	(20,541)	(4,750)
Net income (loss)									(2,097)	(10,065)	(2,328)
Amortization of fair value increments									(9,448)	(9,730)	(9,632)
Income and mining tax recovery (note 19)									2,791	7,930	11,916
Loss from investment in MSC, net of amortization									$ (8,754)	$ (11,865)	$ (44)
Summarized key financial information (as a percent)									100.00%
Ownership interest (as a percent)	49.00%								49.00%