Interest Expense (Tables)

3 Months Ended

Mar. 31, 2015

Interest Costs Incurred [Abstract]

Interest income and expense

			Three Months Ended
			March 31,
			2015		2014
Senior notes			$	9,563	$	12,015
Credit facility unutilized fee				735		661
Federal coal lease obligations imputed interest				1,359		2,612
Amortization of deferred financing costs and
	original issue discount			1,064		1,137
Other				47		75
		Subtotal		12,768		16,500
Premium on early retirement of debt				—		13,837
Write-off of deferred financing costs
	and original issue discount			—		7,338
Other				—		348
		Total cost of early retirement of debt and refinancings		—		21,522
Total interest expense				12,768		38,022
Less interest capitalized				(100)		(28)
Net interest expense			$	12,668	$	37,994