CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS Percentage	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenues
Total revenues (as a percent)	100.00%	100.00%
Cost of revenues
Labor and other operating expenses (as a percent)	66.20%	68.20%
Depreciation, depletion and amortization (as a percent)	10.70%	11.80%
Total cost of revenues (as a percent)	76.90%	80.00%
Gross profit (as a percent)	23.10%	20.00%
Selling, general and administrative expenses (as a percent)	7.10%	7.10%
Operating profit (as a percent)	16.00%	12.90%
Other (income) expense
Interest expense (as a percent)	0.20%	0.20%
Interest and other income, net (as a percent)	(1.30%)	(1.00%)
Total other (income) expense (as a percent)	(1.10%)	(0.80%)
Income before income tax expense (as a percent)	17.10%	13.70%
Income tax expense (as a percent)	3.50%	1.60%
Net income (as a percent)	13.60%	12.10%
Lime and limestone operations
Revenues
Total revenues (as a percent)	99.10%	98.40%
Natural gas interests
Revenues
Total revenues (as a percent)	0.90%	1.60%