Inventory and Ore on Leach Pads (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory, Finished Goods, Net of Reserves	$ 11,062	$ 6,831
Other Inventory, Net of Reserves	17,783	18,803
Inventory, Supplies, Net of Reserves	32,878	32,596
Inventory	61,723	58,230
Ore on Leach Pad, Current	75,584	73,752
Ore on leach pads, noncurrent	67,430	65,393
Inventory, Ore Stockpiles on Leach Pads, Gross	143,014	139,145
Inventory and Ore on Leach Pads	$ 204,737	$ 197,375