Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Revenues
Revenues	$ 189,255	$ 160,704	$ 158,277
Cost of revenues
Labor and other operating expenses	109,365	93,738	99,207
Depreciation, depletion and amortization	20,630	19,379	17,394
Total cost of revenues	129,995	113,117	116,601
Gross profit	59,260	47,587	41,676
Selling, general and administrative expenses	12,843	12,168	11,500
Impairment of long-lived assets		1,550	930
Operating profit	46,417	33,869	29,246
Other expense (income)
Interest expense	250	248	244
Interest and other income, net	(351)	(451)	(1,898)
Total other expense (income)	(101)	(203)	(1,654)
Income before income tax expense	46,518	34,072	30,900
Income tax expense	9,473	5,849	4,844
Net income	$ 37,045	$ 28,223	$ 26,056
Net income per share of common stock
Basic (in dollars per share)	$ 6.55	$ 5.01	$ 4.64
Diluted (in dollars per share)	$ 6.54	$ 5.00	$ 4.64