Note 14 - Major Customers (Tables)

12 Months Ended

Dec. 31, 2022

Notes Tables

Schedules of Concentration of Risk, by Risk Factor [Table Text Block]

	For the Year Ended December 31,
	2022					2021					2020
(In thousands)	Revenues		Percent			Revenues		Percent			Revenues		Percent
Alpha Metallurgical Resources, Inc. (1)	$	102,352		26	%	$	49,440		23	%	$	33,227		24	%
Foresight (1) (2)		65,597		17	%		37,366		17	%		35,704		26	%