CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS Percentage	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues
Revenues (as a percent)	100.00%	100.00%	100.00%	100.00%
Cost of revenues
Labor and other operating expenses (as a percent)	54.50%	57.50%	55.10%	60.70%
Depreciation, depletion and amortization (as a percent)	7.90%	8.50%	8.10%	9.20%
Total cost of revenues (as a percent)	62.40%	66.00%	63.20%	69.90%
Gross profit (as a percent)	37.60%	34.00%	36.80%	30.10%
Selling, general and administrative expenses (as a percent)	5.80%	5.30%	6.00%	6.20%
Operating profit (as a percent)	31.80%	28.70%	30.80%	23.90%
Other expense (income)
Other (income) expense, net	(2.90%)	(0.80%)	(2.60%)	(0.40%)
Income before income tax expense (as a percent)	34.70%	29.50%	33.40%	24.30%
Income tax expense (as a percent)	7.00%	5.80%	6.70%	4.80%
Net income (as a percent)	27.70%	23.70%	26.70%	19.50%