Consolidated Statement of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Revenue:
Revenue		$ 293,557	$ 271,633
Costs and expenses:
Operating costs and expenses		215,363	190,150
DD&A		44,167	38,495
ARO accretion		1,167	861
Exploration costs		1,185	854
SG&A		11,841	14,978
Interest	[1]	16,288	12,413
Total costs and expenses		290,011	257,751
Income before income taxes		3,546	13,882
Less income tax benefit
Current		(1,788)	(2,748)
Deferred		(2,287)	(16,446)
Total income tax benefit		(4,075)	(19,194)
Net income		$ 7,621	$ 33,076
Net income per share: (Note 11)
Basic and diluted (in Dollars per share)		$ 0.25	$ 1.08
Weighted average shares outstanding:
Basic and diluted (in Shares)		30,074	29,661
Interest expense on net change in estimated fair value of interest rate swaps		$ 2,182	$ (723)
Coal Sales [Member]
Revenue:
Revenue		291,783	268,202
Other Revenue [Member]
Revenue:
Revenue		$ 1,774	$ 3,431

[1] Included in interest expense is the change in the estimated fair value of our interest rate swaps. Such amounts were $2,182 and $(723) for 2018 and 2017, respectively.