INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE - Summary of Operating Results from MSC (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Income taxes recovery	$ 607	$ 1,619	$ 3,330	$ 15,103
(Loss) income from investment in MSC, net of amortization	4,693	(1,641)	13,789	(3,964)
MSC
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Net sales	72,116	45,357	182,769	141,106
Production costs applicable to sales	(49,345)	(41,767)	(125,904)	(119,940)
Net (loss) income	$ 12,072	$ (3,375)	$ 31,293	$ (5,185)
Ownership interest (as a percent)	49.00%	49.00%	49.00%	49.00%
Net (loss) income	$ 5,916	$ (1,654)	$ 15,334	$ (2,541)	$ (2,859)
Amortization of fair value increments	(2,914)	(1,617)	(9,370)	(7,705)	(10,669)
Income taxes recovery	1,691	1,630	7,825	6,282	$ 15,942
(Loss) income from investment in MSC, net of amortization	$ 4,693	$ (1,641)	$ 13,789	$ (3,964)