Segment Reporting (Details 1) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting [Abstract]
Assets, Net	[1]	$ 1,550,671	$ 1,344,553	$ 1,045,722
Cash and cash equivalents		115,081	192,032	$ 118,312
Other assets		46,748	164,590
TOTAL ASSETS		$ 1,712,500	$ 1,701,175

[1] Segment assets include receivables, prepaids, inventories, property, plant and equipment, and mineral interest