Segment Reporting (Details 1) - USD ($) $ in Thousands	Sep. 30, 2017		Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016		Dec. 31, 2015
Segment Reporting [Abstract]
Assets, Net	$ 1,092,430	[1]		$ 1,122,038		$ 1,109,910	[2]
Cash and cash equivalents	236,221		$ 250,038	162,182	$ 222,517	$ 257,591		$ 200,714
Other assets	73,441			34,689
TOTAL ASSETS	$ 1,402,092			$ 1,318,909

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

[2] Segment assets include receivables, prepaids, inventories, property, plant and equipment, and mineral interests