Segment Reporting (Details 1) - USD ($) $ in Thousands	Jun. 30, 2017		Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016		Mar. 31, 2016	Dec. 31, 2015
Segment Reporting [Abstract]
Assets, Net	$ 1,096,251	[1]		$ 1,122,038	$ 1,113,959	[2]
Cash and cash equivalents	250,038		$ 210,033	162,182	$ 257,591		$ 173,389	$ 200,714
Other assets	48,359			34,689
TOTAL ASSETS	$ 1,394,648			$ 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