Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net loss	$ (8,127)	$ (13,662)	$ (36,875)
Other comprehensive income (loss):
Amortization of accumulated actuarial gains or losses, pension	3,490	2,960	1,647
Adjustments to accumulated actuarial losses and transition obligations, pension	28,974	(9,812)	(15,798)
Amortization of accumulated actuarial gains or losses, transition obligations, and prior service costs, postretirement medical benefit	4,005	2,572	(288)
Adjustments to accumulated actuarial gains and transition obligations, postretirement medical benefits	53,230	(22,342)	(49,136)
Tax effect of other comprehensive income gains	(4,892)	0	0
Unrealized and realized gains and losses on available-for-sale securities	(57)	(268)	(200)
Other comprehensive income (loss)	84,750	(26,890)	(63,775)
Comprehensive income (loss) attributable to Westmoreland Coal Company	$ 76,623	$ (40,552)	$ (100,650)