CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Revenues
Revenues	$ 49,162	$ 37,547	$ 90,836	$ 75,987
Cost of revenues
Labor and other operating expenses	27,200	22,447	51,793	46,409
Depreciation, depletion and amortization	5,167	4,743	10,443	9,344
Total cost of revenues	32,367	27,190	62,236	55,753
Gross profit	16,795	10,357	28,600	20,234
Selling, general and administrative expenses	2,957	2,881	6,024	6,100
Operating profit	13,838	7,476	22,576	14,134
Other expense (income)
Interest expense	62	62	124	124
Interest and other income, net	(91)	(104)	(125)	(351)
Total other expense (income)	(29)	(42)	(1)	(227)
Income before income tax expense	13,867	7,518	22,577	14,361
Income tax expense	2,774	1,417	4,453	2,716
Net income	$ 11,093	$ 6,101	$ 18,124	$ 11,645
Net income per share of common stock
Basic (in dollars per share)	$ 1.96	$ 1.08	$ 3.21	$ 2.07
Diluted (in dollars per share)	$ 1.96	$ 1.08	$ 3.20	$ 2.07