Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Net loss	$ (4,087)	$ (222)
Other comprehensive income:
Amortization of accumulated actuarial gains or losses, pension	741	729
Amortization of accumulated actuarial gains or losses, transition obligations, and prior service costs, postretirement medical benefit	1,001	643
Tax effect of other comprehensive income gains	0	(504)
Unrealized and realized gains and losses on available-for-sale securities	0	(69)
Other comprehensive income	1,742	799
Comprehensive income (loss) attributable to Westmoreland Coal Company	$ (2,345)	$ 577