LINES OF CREDIT AND LONG-TERM DEBT - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Revolving credit agreements:
Loss on extinguishment of debt	$ 0	$ 0	$ (64,000)	$ 0
Payments to purchase equipment under capital leases			2,700,000
Principal amount of capital lease obligation extinguished			2,500,000
Westmoreland Mining, LLC
Revolving credit agreements:
Line of credit facility maximum borrowing capacity	25,000,000		25,000,000
10.75% Senior Notes
Debt Instrument [Line Items]
Stated interest rate (percent)	10.75%		10.75%
Revolving credit agreements:
Repurchase of Senior Notes			500,000
Principal amount of notes extinguished			500,000
Loss on extinguishment of debt			100,000
Revolving Credit Facility | Westmoreland Mining, LLC
Revolving credit agreements:
Debt issuance costs capitalized	$ 200,000