CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS Percentage	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Revenues
Revenues (as a percent)	100.00%	100.00%
Cost of revenues
Labor and other operating expenses (as a percent)	55.50%	61.40%
Depreciation, depletion and amortization (as a percent)	8.60%	10.20%
Total cost of revenues (as a percent)	64.10%	71.60%
Gross profit (as a percent)	35.90%	28.40%
Selling, general and administrative expenses (as a percent)	6.20%	7.10%
Operating profit (as a percent)	29.70%	21.30%
Other expense (income)
Interest expense (as a percent)	0.10%	0.10%
Interest and other income, net (as a percent)	(2.40%)	(0.10%)
Total other expense (income) (as a percent)	(2.30%)	0.00%
Income before income tax expense (as a percent)	32.00%	21.30%
Income tax expense (as a percent)	6.40%	4.30%
Net income (as a percent)	25.60%	17.00%