Segment Reporting (Details 1) - USD ($) $ in Thousands	Mar. 31, 2021		Dec. 31, 2020	Mar. 31, 2020
Segment Reporting [Abstract]
Assets, Net	$ 1,283,284	[1]	$ 1,232,153	$ 1,203,594	[1]
Cash and cash equivalents	154,066		92,794	$ 52,895
Other assets	78,065		79,030
TOTAL ASSETS	$ 1,515,415		$ 1,403,977

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