ACCRUED WORKERS' COMPENSATION AND PNEUMOCONIOSIS BENEFITS (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Accrued Workers Compensation And Pneumoconiosis Benefits
Total adjustments	$ 32,545		$ (1,804)		$ (21,739)
Black Lung
Accrued Workers Compensation And Pneumoconiosis Benefits
Net actuarial gain	16,750		2,156		(4,570)
Reversal of amortization item, net actuarial loss	670	[1]	776	[1]	(223)	[1]
Total adjustments	$ 17,420		$ 2,932		$ (4,793)

[1] Amortization of actuarial gain or loss is included in the computation of net periodic benefit cost (see Notes 13 and 17 for additional details).