Interest Expense (Tables)

6 Months Ended

Jun. 30, 2017

Interest Costs Incurred [Abstract]

Interest Expense

			Three Months Ended				Six Months Ended
			June 30,				June 30,
			2017		2016		2017		2016
Senior notes			$	6,582	$	9,563	$	14,568	$	19,125
Credit facility unutilized fee				1,197		1,059		2,380		1,827
Federal coal lease obligations imputed interest				86		84		171		166
Amortization of deferred financing costs and
	original issue discount			1,946		1,051		3,932		2,102
Other				55		75		145		135
		Subtotal		9,866		11,831		21,196		23,354
Premium on early retirement of debt				—		—		880		—
Write-off of deferred financing costs
	and original issue discount			—		—		702		—
	Total cost of early retirement of debt and refinancings			—		—		1,582		—
Total interest expense				9,866		11,831		22,778		23,354
Less interest capitalized				—		(545)		—		(1,016)
Net interest expense			$	9,866	$	11,286	$	22,778	$	22,338