RESTRUCTURING CHARGES (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Restructuring Reserve [Roll Forward]
Restructuring charges	$ 14,989,000	$ 5,078,000	$ 0
ROVA I and ROVA II Contracts [Member]
Restructuring Cost and Reserve [Line Items]
Remaining Period of Contract		5
Restructuring Reserve [Roll Forward]
Beginning balance	5,100,000
Restructuring charges	500,000
Restructuring Payments	5,200,000
Ending balance	400,000	5,100,000
Sherritt International Corporation and Westmoreland Resources LP [Member]
Restructuring Reserve [Roll Forward]
Beginning balance	0
Restructuring charges	14,500,000
Restructuring Payments	5,700,000
Ending balance	$ 8,800,000