COMMITMENTS AND CONTINGENCIES (Narrative) (Details) - USD ($)	1 Months Ended
Apr. 30, 2014	Mar. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Civil Penalties	$ 37,500
Loss Contingency, Estimate of Possible Loss		$ 12,980,000	$ 16,150,000
Asset Retirement Obligation		8,500,000	8,573,000	$ 5,683,000
Surety Bond [Member]
Asset Retirement Obligation		$ 32,300,000	$ 27,400,000

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Asset Retirement Obligation
-URI http://asc.fasb.org/extlink&oid=6505190

Name:	us-gaap_AssetRetirementObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant