Interest Expense (Tables)

9 Months Ended

Sep. 30, 2015

Interest Costs Incurred [Abstract]

Interest income and expense

			Three Months Ended				Nine Months Ended
			September 30,				September 30,
			2015		2014		2015		2014
Senior notes			$	9,563	$	9,563	$	28,688	$	31,140
Credit facility unutilized fee				643		614		2,027		1,836
Federal coal lease obligations imputed interest				35		1,478		2,883		6,702
Amortization of deferred financing costs and
	original issue discount			1,040		1,021		3,133		3,185
Other				44		64		137		209
		Subtotal		11,325		12,740		36,868		43,072
Premium on early retirement of debt				—		—		—		13,837
Write-off of deferred financing costs
	and original issue discount			—		—		—		7,338
Other				—		—		—		364
		Total cost of early retirement of debt and refinancings		—		—		—		21,538
Total interest expense				11,325		12,740		36,868		64,610
Less interest capitalized				(340)		(39)		(594)		(102)
Net interest expense			$	10,985	$	12,701	$	36,274	$	64,508