CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenues
Total revenues	$ 39,242	$ 36,518	$ 74,529	$ 72,671
Cost of revenues
Labor and other operating expenses	25,317	23,626	49,390	47,305
Depreciation, depletion and amortization	4,288	4,054	8,465	8,290
Total cost of revenues	29,605	27,680	57,855	55,595
Gross profit	9,637	8,838	16,674	17,076
Selling, general and administrative expenses	2,565	2,518	5,066	4,938
Operating profit	7,072	6,320	11,608	12,138
Other (income) expense
Interest expense	63	59	125	118
Interest and other income, net	(459)	(225)	(812)	(404)
Total other (income) expense	(396)	(166)	(687)	(286)
Income before income tax expense	7,468	6,486	12,295	12,424
Income tax expense	830	1,208	1,395	2,526
Net income	$ 6,638	$ 5,278	$ 10,900	$ 9,898
Net income per share of common stock
Basic (in dollars per share)	$ 1.19	$ 0.95	$ 1.95	$ 1.77
Diluted (in dollars per share)	1.18	0.94	1.95	1.77
Cash dividends per share of common stock (in dollars per share)	$ 0.135	$ 0.135	$ 0.270	$ 0.270
Lime and limestone operations
Revenues
Total revenues	$ 38,557	$ 35,965	$ 73,271	$ 71,482
Natural gas interests
Revenues
Total revenues	$ 685	$ 553	$ 1,258	$ 1,189