Segment Reporting (Details 1) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015		Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Assets, Net	$ 1,109,910			$ 1,103,310	$ 1,458,659	[1]
Cash and cash equivalents	222,517	$ 257,591	$ 257,591	200,714	$ 205,708		$ 205,868	$ 205,868	$ 270,861
Other assets	38,515			28,465
TOTAL ASSETS	$ 1,370,942			$ 1,332,489

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