Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net loss	$ (173,180)us-gaap_ProfitLoss	$ (8,127)us-gaap_ProfitLoss	$ (13,662)us-gaap_ProfitLoss
Pension and other postretirement plans:
Amortization of accumulated actuarial gains or losses, pension	983	3,490	2,960
Adjustments to accumulated actuarial losses and transition obligations, pension	(24,793)	28,974	(9,812)
Amortization of accumulated actuarial gains or losses, transition obligations, and prior service costs, postretirement medical benefits	18	4,005	2,572
Adjustments to accumulated actuarial gains, postretirement medical benefits	(19,442)	53,230	(22,342)
Tax effect of other comprehensive income gains	0us-gaap_OtherComprehensiveIncomeLossTax	(4,892)us-gaap_OtherComprehensiveIncomeLossTax	0us-gaap_OtherComprehensiveIncomeLossTax
Change in foreign currency translation adjustment	(17,880)	0	0
Unrealized and realized gains and losses on available-for-sale securities	413	(57)	(268)
Other comprehensive income (loss)	(60,701)	84,750	(26,890)
Comprehensive income (loss) attributable to Westmoreland Coal Company	$ (233,881)	$ 76,623	$ (40,552)

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount after tax and reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss).

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The adjustment out of other comprehensive income for actuarial gains or losses recognized as a component of net period benefit cost during the period.

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Adjustments to accumulated actuarial gains and transition obligations, postretirement medical benefits

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