PENSION AND OTHER SAVING PLANS - Information on Plan Assets (Details) (Pension [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Unrealized (loss) gain	$ 14,392	$ 18,414
Settlements	(12,795)	0
Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	30,639	2,717
Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	130,084	131,182
Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, beginning balance	250	614
Unrealized (loss) gain	19	5
Settlements	(45)	(369)
Plan assets, ending balance	224	250
Large-cap pooled separate accounts [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[1]
Large-cap pooled separate accounts [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	47,092	48,983	[1]
Large-cap pooled separate accounts [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[1]
International blend [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[2]
International blend [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	7,290	18,191	[2]
International blend [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[2]
Fixed income domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Corporate bond maturity period	15 years
Fixed income domestic [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[3]
Fixed income domestic [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	23,057	40,944	[3]
Fixed income domestic [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[3]
Fixed income long term [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[4]
Fixed income long term [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	47,299	17,797	[4]
Fixed income long term [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[4]
Stable value [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[5]
Stable value [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	5,346	5,267	[5]
Stable value [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0	[5]
Debt securities funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation - minimum	40.00%
Target asset allocation - maximum	80.00%
Registered investment companies - growth fund [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	16,490
Registered investment companies - growth fund [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0
Registered investment companies - growth fund [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0
Limited partnerships and limited liability companies [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Limited partnerships and limited liability companies [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Limited partnerships and limited liability companies [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	224	250
Westmoreland Coal common stock [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	1,539	2,255
Westmoreland Coal common stock [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Westmoreland Coal common stock [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation - minimum	0.00%
Target asset allocation - maximum	10.00%
Cash and cash equivalents [Member] | Quoted prices in active markets for identical assets - Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	12,610	462
Cash and cash equivalents [Member] | Significant other observable inputs - Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Cash and cash equivalents [Member] | Significant unobservable inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	0	0
Equity funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation - minimum	20.00%
Target asset allocation - maximum	60.00%
Other asset category [Member]
Defined Benefit Plan Disclosure [Line Items]
Target asset allocation - minimum	0.00%
Target asset allocation - maximum	10.00%
Fair Value [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	160,947	134,149
Fair Value [Member] | Large-cap pooled separate accounts [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	47,092	48,983	[1]
Fair Value [Member] | International blend [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	7,290	18,191	[2]
Fair Value [Member] | Fixed income domestic [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	23,057	40,944	[3]
Fair Value [Member] | Fixed income long term [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	47,299	17,797	[4]
Fair Value [Member] | Stable value [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	5,346	5,267	[5]
Fair Value [Member] | Registered investment companies - growth fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	16,490
Fair Value [Member] | Limited partnerships and limited liability companies [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	224	250
Fair Value [Member] | Westmoreland Coal common stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	1,539	2,255
Fair Value [Member] | Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, ending balance	$ 12,610	$ 462

[1] Large-cap blend funds seek to provide long-term growth of capital. They seek to provide investment results that approximate the performance of the Standard & Poor’s Composite 1500 Index.

[2] International blends seek to have a diversified portfolio of investments, invading fixed-income and equity-focused investments in international markets.

[3] Fixed income domestic funds seek to invest in high-quality corporate bonds with over 15 years to maturity.

[4] Fixed income long term bond funds seek to achieve performance results similar to the Barclays Capital U.S. Aggregate Bond Index. This fund invests primarily in corporate and government bonds.

[5] The stable value fund seeks to invest in publicly traded and privately placed debt securities and mortgage loans, and to a lesser extent, real estate and other equity investments in order to provide a guaranteed rate of return.The Company’s Level 1 assets include securities held by registered investment companies and its common stock,