INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Changes in Company's Investment in MSC (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in the investment in MSC
Investment in MSC, beginning of period	$ 127,814
Income and mining tax recovery (note 19)	(3,844)	$ (2,770)	$ (15,369)
Dividend distribution received	(8,877)	(10,385)	(12,212)
Investment in MSC, end of period	110,183	127,814
MSC
Change in the investment in MSC
Investment in MSC, beginning of period	127,814	150,064
Attributable net loss from MSC	(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
Dividend distribution received	(8,877)	(10,385)
Investment in MSC, end of period	$ 110,183	$ 127,814	$ 150,064