Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues	$ 382,261	$ 619,467	$ 1,107,014	$ 1,744,872
Costs, expenses and other operating
Cost of sales (exclusive of items shown separately below)	345,539	491,004	1,036,886	1,380,563
Depreciation, depletion and amortization	32,630	30,249	94,105	82,122
Accretion on asset retirement obligations	4,947	5,137	14,939	15,411
Change in fair value of coal derivatives and coal trading activities, net	2,649	1,530	3,263	(19,851)
Selling, general and administrative expenses	21,541	24,566	64,024	73,864
Costs related to proposed joint venture with Peabody Energy	4,423	3,754	15,938	6,772
Asset impairment	163,088		163,088
Severance costs related to voluntary separation plan	18		13,283
Gain on property insurance recovery related to Mountain Laurel longwall			(23,518)
(Gain) loss on divestitures			(1,369)	4,304
Preference Rights Lease Application settlement income		(39,000)	(23,518)	(39,000)
Other operating income, net	(4,894)	(4,254)	(16,768)	(9,143)
Costs, expenses and other operating	569,941	512,986	1,363,871	1,495,042
Income (loss) from operations	(187,680)	106,481	(256,857)	249,830
Interest expense, net
Interest expense	(2,989)	(4,049)	(9,900)	(12,856)
Interest and investment income	459	3,709	3,511	7,940
Interest expense, net	(2,530)	(340)	(6,389)	(4,916)
Income (loss) before nonoperating expenses	(190,210)	106,141	(263,246)	244,914
Nonoperating (expenses) income
Non-service related pension and postretirement benefit costs	(878)	975	(3,076)	(2,127)
Reorganization items, net			26	71
Nonoperating (expenses) income	(878)	975	(3,050)	(2,056)
Income (loss) before income taxes	(191,088)	107,116	(266,296)	242,858
Provision for (benefit from) income taxes	379	347	(206)	508
Net income (loss)	$ (191,467)	$ 106,769	$ (266,090)	$ 242,350
Net income (loss) per common share
Basic earnings (loss) per common share (in dollars per share)	$ (12.64)	$ 6.79	$ (17.57)	$ 14.61
Diluted earnings (loss) per common share (in dollars per share)	$ (12.64)	$ 6.34	$ (17.57)	$ 13.66
Weighted average shares outstanding
Basic weighted average shares outstanding (in shares)	15,147	15,736	15,144	16,591
Diluted weighted average shares outstanding (in shares)	15,147	16,852	15,144	17,744
Dividends declared per common share (in dollars per share)		$ 0.45	$ 0.50	$ 1.35
Dal-Tex and Briar Branch Properties
Costs, expenses and other operating
(Gain) loss on divestitures			$ (1,369)	$ 4,304