CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS Percentage	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues
Lime and limestone operations (as a percent)	98.60%	98.40%	98.60%	98.00%
Natural gas (as a percent)	1.40%	1.60%	1.40%	2.00%
Total revenues (as a percent)	100.00%	100.00%	100.00%	100.00%
Cost of revenues:
Labor and other operating expenses (as a percent)	62.30%	61.30%	64.30%	64.80%
Depreciation, depletion and amortization (as a percent)	10.40%	10.70%	11.30%	11.80%
Total cost of revenues (as a percent)	72.70%	72.00%	75.60%	76.60%
Gross profit (as a percent)	27.30%	28.00%	24.40%	23.40%
Selling, general and administrative expenses (as a percent)	6.40%	6.70%	6.90%	7.30%
Operating profit (as a percent)	20.90%	21.40%	17.50%	16.10%
Other expenses (income):
Interest expense (as a percent)	0.20%	0.10%	0.10%	1.00%
Other (income) expense, net (as a percent)	(0.30%)	(0.10%)	(0.20%)	0.70%
Total other expense (income) (as a percent)	(0.10%)	0.00%	(0.10%)	1.70%
Income before income taxes (as a percent)	21.00%	21.40%	17.60%	14.40%
Income tax expense (as a percent)	5.30%	6.00%	4.40%	3.80%
Net income (as a percent)	15.70%	15.30%	13.20%	10.70%