CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenues
Revenues	$ 52,311	$ 43,727	$ 143,147	$ 119,714
Cost of revenues
Labor and other operating expenses	29,981	24,665	81,774	71,074
Depreciation, depletion and amortization	4,989	4,880	15,432	14,224
Total cost of revenues	34,970	29,545	97,206	85,298
Gross profit	17,341	14,182	45,941	34,416
Selling, general and administrative expenses	3,145	2,909	9,169	9,009
Operating profit	14,196	11,273	36,772	25,407
Other expense (income)
Interest expense	63	62	187	186
Interest and other income, net	(147)	(49)	(272)	(400)
Total other expense (income)	(84)	13	(85)	(214)
Income before income tax expense	14,280	11,260	36,857	25,621
Income tax expense	2,972	1,936	7,425	4,652
Net income	$ 11,308	$ 9,324	$ 29,432	$ 20,969
Net income per share of common stock
Basic (in dollars per share)	$ 2.00	$ 1.66	$ 5.20	$ 3.73
Diluted (in dollars per share)	$ 1.99	$ 1.65	$ 5.19	$ 3.72