WORKERS' COMPENSATION AND PNEUMOCONIOSIS (Details 2) (Black Lung, USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Black Lung
Accrued Workers Compensation And Pneumoconiosis Benefits
Service cost	$ 953		$ 960		$ 2,858		$ 2,795
Interest cost	563		598		1,690		1,773
Amortization of net loss	168	[1]	194	[1]	503	[1]	582	[1]
Net periodic benefit cost	$ 1,684		$ 1,752		$ 5,051		$ 5,150

[1] Amortization of net loss is included in the operating expenses line item within our condensed consolidated statements of income.