SUBSEQUENT EVENTS (Details) - San Juan Coal Company [Member] - Subsequent Event [Member] $ in Millions	Jan. 31, 2016 USD ($)
Acquisition [Abstract]
Cash purchase price paid by Westmoreland San Juan, LLC	$ 127
Loan for acquisition	$ 125
Spread on basis, percentage	7.25%

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration