SUPPLEMENTAL CONSOLIDATING FINANCIAL INFORMATION - Supplemental Consolidating Balance Sheet Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Current assets:
Cash and cash equivalents	$ 61,110	$ 31,610	$ 30,783	$ 5,775
Receivables:
Trade	66,196	60,037
Contractual third-party reclamation receivables	8,487	10,207
Intercompany receivable/payable	0	0
Other	5,086	3,220
Total receivables	79,769	73,464
Inventories	39,972	37,734
Deferred income taxes	0
Restricted investments and bond collateral	5,998	0
Other current assets	18,190	16,504
Total current assets	205,039	159,312
Property, plant and equipment:
Land and mineral rights	278,188	261,741
Plant and equipment	657,696	635,720
Gross property, plant and equipment	935,884	897,461
Less accumulated depreciation, depletion and amortization	445,848	384,621
Net property, plant and equipment	490,036	512,840
Advanced coal royalties	7,311	4,316
Reclamation Deposits	74,921	72,718
Restricted investments and bond collateral	69,235	87,209
Contractual third-party reclamation receivables, less current portion	88,303	84,158
Intangible assets	1,520	3,203
Investment in subsidiaries	0	0
Other assets	10,320	12,359
Total Assets	946,685	936,115	759,172
Current liabilities
Current installments of long-term debt	44,343	23,791
Accounts payable and accrued expenses:
Trade	57,507	52,093
Production taxes	41,905	33,228
Workers' compensation	717	820
Postretirement medical benefits	13,955	14,068
SERP	390	390
Deferred revenue	14,068	12,822
Asset retirement obligations	23,353	22,238
Other current liabilities	16,790	11,462
Total current liabilities	213,028	170,912
Long-term debt, less current installments	295,494	337,198
Workers' compensation, less current portion	6,744	8,710
Excess of black lung benefit obligation over trust assets	8,675	8,356
Postretirement medical benefits, less current portion	270,374	319,775
Pension and SERP obligations, less current portion	24,176	54,250
Deferred revenue, less current portion	46,567	56,891
Asset retirement obligations, less current portion	256,511	241,609
Intangible liabilities	5,606	6,625
Other liabilities	7,389	18,020
Intercompany receivable/payable	0	0
Total liabilities	1,134,564	1,222,346
Shareholders' deficit:
Preferred stock	160	160
Common stock	36,479	35,502
Other paid-in capital	134,861	130,852
Accumulated other comprehensive loss	(63,595)	(148,345)	(121,455)	(57,680)
Accumulated earnings (deficit)	(295,784)	(289,727)
Total Westmoreland Coal Company shareholders' deficit	(187,879)	(271,558)
Noncontrolling interest	0	(14,673)
Total equity (deficit)	(187,879)	(286,231)	(249,858)	(162,355)
Total Liabilities and Shareholders' Deficit	946,685	936,115
Parent Company [Member]
Current assets:
Cash and cash equivalents	25,326	14,836	26,141	271
Receivables:
Trade	0	0
Contractual third-party reclamation receivables	0	0
Intercompany receivable/payable	(3,568)	(8,002)
Other	95	77
Total receivables	(3,473)	(7,925)
Inventories	0	0
Deferred income taxes	0
Restricted investments and bond collateral	0
Other current assets	6,115	739
Total current assets	27,968	7,650
Property, plant and equipment:
Land and mineral rights	0	0
Plant and equipment	3,939	3,198
Gross property, plant and equipment	3,939	3,198
Less accumulated depreciation, depletion and amortization	2,705	2,364
Net property, plant and equipment	1,234	834
Advanced coal royalties	0	0
Reclamation Deposits	0	0
Restricted investments and bond collateral	15,134	15,183
Contractual third-party reclamation receivables, less current portion	0	0
Intangible assets	0	0
Investment in subsidiaries	266,847	248,565
Other assets	8,636	10,267
Total Assets	319,819	282,499
Current liabilities
Current installments of long-term debt	20,392	(1,548)
Accounts payable and accrued expenses:
Trade	4,122	4,707
Production taxes	0	0
Workers' compensation	717	820
Postretirement medical benefits	12,042	12,494
SERP	390	390
Deferred revenue	0	0
Asset retirement obligations	0	0
Other current liabilities	11,302	11,312
Total current liabilities	48,965	28,175
Long-term debt, less current installments	224,582	245,456
Workers' compensation, less current portion	6,744	8,710
Excess of black lung benefit obligation over trust assets	8,675	8,356
Postretirement medical benefits, less current portion	185,858	224,336
Pension and SERP obligations, less current portion	13,069	29,265
Deferred revenue, less current portion	0	0
Asset retirement obligations, less current portion	0	0
Intangible liabilities	0	0
Other liabilities	5,939	701
Intercompany receivable/payable	13,866	23,731
Total liabilities	507,698	568,730
Shareholders' deficit:
Preferred stock	160	160
Common stock	36,479	35,502
Other paid-in capital	134,861	130,852
Accumulated other comprehensive loss	(63,595)	(148,345)
Accumulated earnings (deficit)	(295,784)	(289,727)
Total Westmoreland Coal Company shareholders' deficit	(187,879)	(271,558)
Noncontrolling interest	0	(14,673)
Total equity (deficit)	(187,879)	(286,231)
Total Liabilities and Shareholders' Deficit	319,819	282,499
Co-Issuer [Member]
Current assets:
Cash and cash equivalents	3,341	4,545	6	880
Receivables:
Trade	12,934	13,018
Contractual third-party reclamation receivables	0	0
Intercompany receivable/payable	0	0
Other	210	0
Total receivables	13,144	13,018
Inventories	6,161	3,047
Deferred income taxes	0
Restricted investments and bond collateral	5,998
Other current assets	143	298
Total current assets	28,787	20,908
Property, plant and equipment:
Land and mineral rights	1,395	1,395
Plant and equipment	220,872	219,857
Gross property, plant and equipment	222,267	221,252
Less accumulated depreciation, depletion and amortization	71,653	61,474
Net property, plant and equipment	150,614	159,778
Advanced coal royalties	0	0
Reclamation Deposits	0	0
Restricted investments and bond collateral	0	5,990
Contractual third-party reclamation receivables, less current portion	0	0
Intangible assets	1,283	2,923
Investment in subsidiaries	0	0
Other assets	0	0
Total Assets	180,684	189,599
Current liabilities
Current installments of long-term debt	0	0
Accounts payable and accrued expenses:
Trade	10,119	4,978
Production taxes	3	3
Workers' compensation	0	0
Postretirement medical benefits	0	0
SERP	0	0
Deferred revenue	9,024	8,788
Asset retirement obligations	0	0
Other current liabilities	5,053	0
Total current liabilities	24,199	13,769
Long-term debt, less current installments	0	0
Workers' compensation, less current portion	0	0
Excess of black lung benefit obligation over trust assets	0	0
Postretirement medical benefits, less current portion	0	0
Pension and SERP obligations, less current portion	99	289
Deferred revenue, less current portion	41,297	50,239
Asset retirement obligations, less current portion	892	829
Intangible liabilities	5,606	6,625
Other liabilities	0	0
Intercompany receivable/payable	0	0
Total liabilities	72,093	71,751
Shareholders' deficit:
Preferred stock	0	0
Common stock	5	5
Other paid-in capital	52,835	52,807
Accumulated other comprehensive loss	(164)	(372)
Accumulated earnings (deficit)	55,915	65,408
Total Westmoreland Coal Company shareholders' deficit	108,591	117,848
Noncontrolling interest	0	0
Total equity (deficit)	108,591	117,848
Total Liabilities and Shareholders' Deficit	180,684	189,599
Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	7,942	5,362	143	0
Receivables:
Trade	17,389	13,428
Contractual third-party reclamation receivables	44	56
Intercompany receivable/payable	4,384	5,667
Other	2,974	16,806
Total receivables	24,791	35,957
Inventories	16,077	16,538
Deferred income taxes	870
Restricted investments and bond collateral	0
Other current assets	6,883	5,550
Total current assets	56,563	63,407
Property, plant and equipment:
Land and mineral rights	104,631	91,741
Plant and equipment	229,998	215,751
Gross property, plant and equipment	334,629	307,492
Less accumulated depreciation, depletion and amortization	132,189	108,151
Net property, plant and equipment	202,440	199,341
Advanced coal royalties	3,000	500
Reclamation Deposits	0	0
Restricted investments and bond collateral	36,619	39,208
Contractual third-party reclamation receivables, less current portion	293	327
Intangible assets	0	0
Investment in subsidiaries	0	(792)
Other assets	586	635
Total Assets	299,501	302,626
Current liabilities
Current installments of long-term debt	2,790	1,939
Accounts payable and accrued expenses:
Trade	12,522	15,163
Production taxes	17,429	10,014
Workers' compensation	0	0
Postretirement medical benefits	329	87
SERP	0	0
Deferred revenue	3,969	2,997
Asset retirement obligations	3,104	3,519
Other current liabilities	317	10
Total current liabilities	40,460	33,729
Long-term debt, less current installments	2,664	2,473
Workers' compensation, less current portion	0	0
Excess of black lung benefit obligation over trust assets	0	0
Postretirement medical benefits, less current portion	49,418	55,981
Pension and SERP obligations, less current portion	9,381	19,346
Deferred revenue, less current portion	0	0
Asset retirement obligations, less current portion	50,472	40,063
Intangible liabilities	0	0
Other liabilities	6,220	15,677
Intercompany receivable/payable	525	(7,972)
Total liabilities	159,140	159,297
Shareholders' deficit:
Preferred stock	0	0
Common stock	110	110
Other paid-in capital	94,370	93,456
Accumulated other comprehensive loss	17,492	(4,987)
Accumulated earnings (deficit)	28,389	54,750
Total Westmoreland Coal Company shareholders' deficit	140,361	143,329
Noncontrolling interest	0	0
Total equity (deficit)	140,361	143,329
Total Liabilities and Shareholders' Deficit	299,501	302,626
Non-Guarantor Subsidiaries [Member]
Current assets:
Cash and cash equivalents	24,501	6,867	4,493	4,624
Receivables:
Trade	35,873	33,591
Contractual third-party reclamation receivables	8,443	10,151
Intercompany receivable/payable	(33,681)	(30,641)
Other	1,831	1,182
Total receivables	12,466	14,283
Inventories	17,735	18,149
Deferred income taxes	0
Restricted investments and bond collateral	0
Other current assets	5,049	9,917
Total current assets	59,751	49,216
Property, plant and equipment:
Land and mineral rights	172,163	168,605
Plant and equipment	202,886	196,914
Gross property, plant and equipment	375,049	365,519
Less accumulated depreciation, depletion and amortization	239,302	212,632
Net property, plant and equipment	135,747	152,887
Advanced coal royalties	4,311	3,816
Reclamation Deposits	74,921	72,718
Restricted investments and bond collateral	17,482	26,828
Contractual third-party reclamation receivables, less current portion	88,010	83,831
Intangible assets	238	280
Investment in subsidiaries	3,770	3,770
Other assets	3,098	3,457
Total Assets	387,328	396,803
Current liabilities
Current installments of long-term debt	21,161	23,400
Accounts payable and accrued expenses:
Trade	30,743	42,085
Production taxes	24,472	23,211
Workers' compensation	0	0
Postretirement medical benefits	1,583	1,487
SERP	0	0
Deferred revenue	1,075	1,037
Asset retirement obligations	20,250	18,719
Other current liabilities	142	144
Total current liabilities	99,426	110,083
Long-term debt, less current installments	70,248	91,269
Workers' compensation, less current portion	0	0
Excess of black lung benefit obligation over trust assets	0	0
Postretirement medical benefits, less current portion	35,098	39,458
Pension and SERP obligations, less current portion	1,627	5,350
Deferred revenue, less current portion	5,271	6,652
Asset retirement obligations, less current portion	205,147	200,717
Intangible liabilities	0	0
Other liabilities	1,450	1,642
Intercompany receivable/payable	6,434	35,787
Total liabilities	424,701	490,958
Shareholders' deficit:
Preferred stock	0	0
Common stock	132	132
Other paid-in capital	64,401	62,539
Accumulated other comprehensive loss	(14,153)	(24,492)
Accumulated earnings (deficit)	(87,753)	(132,334)
Total Westmoreland Coal Company shareholders' deficit	(37,373)	(94,155)
Noncontrolling interest	0	0
Total equity (deficit)	(37,373)	(94,155)
Total Liabilities and Shareholders' Deficit	387,328	396,803
Consolidating Adjustments [Member]
Current assets:
Cash and cash equivalents	0	0	0	0
Receivables:
Trade	0	0
Contractual third-party reclamation receivables	0	0
Intercompany receivable/payable	32,865	32,976
Other	(24)	(14,845)
Total receivables	32,841	18,131
Inventories	(1)	0
Deferred income taxes	(870)
Restricted investments and bond collateral	0
Other current assets	0	0
Total current assets	31,970	18,131
Property, plant and equipment:
Land and mineral rights	(1)	0
Plant and equipment	1	0
Gross property, plant and equipment	0	0
Less accumulated depreciation, depletion and amortization	(1)	0
Net property, plant and equipment	1	0
Advanced coal royalties	0	0
Reclamation Deposits	0	0
Restricted investments and bond collateral	0	0
Contractual third-party reclamation receivables, less current portion	0	0
Intangible assets	(1)	0
Investment in subsidiaries	(270,617)	(251,543)
Other assets	(2,000)	(2,000)
Total Assets	(240,647)	(235,412)
Current liabilities
Current installments of long-term debt	0	0
Accounts payable and accrued expenses:
Trade	1	(14,840)
Production taxes	1	0
Workers' compensation	0	0
Postretirement medical benefits	1	0
SERP	0	0
Deferred revenue	0	0
Asset retirement obligations	(1)	0
Other current liabilities	(24)	(4)
Total current liabilities	(22)	(14,844)
Long-term debt, less current installments	(2,000)	(2,000)
Workers' compensation, less current portion	0	0
Excess of black lung benefit obligation over trust assets	0	0
Postretirement medical benefits, less current portion	0	0
Pension and SERP obligations, less current portion	0	0
Deferred revenue, less current portion	(1)	0
Asset retirement obligations, less current portion	0	0
Intangible liabilities	0	0
Other liabilities	(6,220)	0
Intercompany receivable/payable	(20,825)	(51,546)
Total liabilities	(29,068)	(68,390)
Shareholders' deficit:
Preferred stock	0	0
Common stock	(247)	(247)
Other paid-in capital	(211,606)	(208,802)
Accumulated other comprehensive loss	(3,175)	29,851
Accumulated earnings (deficit)	3,449	12,176
Total Westmoreland Coal Company shareholders' deficit	(211,579)	(167,022)
Noncontrolling interest	0	0
Total equity (deficit)	(211,579)	(167,022)
Total Liabilities and Shareholders' Deficit	$ (240,647)	$ (235,412)