Revenue Recognition (Tables)

9 Months Ended

Sep. 30, 2020

Revenue from Contract with Customer [Abstract]

Disaggregation of Revenue

The following table disaggregates revenue by major sources:

	THREE MONTHS ENDED				NINE MONTHS ENDED
	SEPTEMBER 30				SEPTEMBER 30
Major Goods/Service Lines	2020		2019		2020		2019
Coal Mining	$	20,395	$	18,799	$	62,896	$	58,119
NAMining	9,443		8,993		33,115		30,496
Minerals Management	2,722		5,022		9,950		25,950
Unallocated Items	904		52		1,257		726
Eliminations	(1,169)		(263)		(1,924)		(1,239)
Total revenues	$	32,295	$	32,603	$	105,294	$	114,052
Timing of Revenue Recognition
Goods transferred at a point in time	$	19,871	$	18,049	$	61,131	$	56,012
Services transferred over time	12,424		14,554		44,163		58,040
Total revenues	$	32,295	$	32,603	$	105,294	$	114,052

Contract Balances

The opening and closing balances of the Company’s current and long-term contract liabilities and receivables are as follows:

	Contract balances
	Trade accounts receivable, net		Contract liability (current)		Contract liability (long-term)
Balance, January 1, 2020	$	15,444	$	944	$	2,153
Balance, September 30, 2020	16,507		941		1,448
Increase (decrease)	$	1,063	$	(3)	$	(705)