Inventory and Ore on Leach Pads (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory, Finished Goods, Net of Reserves	$ 8,778	$ 6,831
Other Inventory, Net of Reserves	20,116	18,803
Inventory, Supplies, Net of Reserves	33,675	32,596
Inventory	62,569	58,230
Ore on Leach Pad, Current	77,515	73,752
Ore on leach pads, noncurrent	67,420	65,393
Inventory, Ore Stockpiles on Leach Pads, Gross	144,935	139,145
Inventory and Ore on Leach Pads	$ 207,504	$ 197,375