Segment Reporting (Details 1) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018
Segment Reporting [Abstract]
Assets, Net	[1]	$ 1,535,465	$ 1,550,671	$ 1,447,904
Cash and cash equivalents		37,907	115,081	$ 123,539
Other assets		103,858	46,748
TOTAL ASSETS		$ 1,677,230	$ 1,712,500

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