Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Total revenues	$ 144,435	$ 144,844	$ 139,282
Cost of revenues
Depreciation, depletion and amortization	17,391	16,340	15,931
Total cost of revenues	113,949	110,464	106,190
Gross profit	30,486	34,380	33,092
Selling, general and administrative expenses, including depreciation and amortization expense of $212, $209 and $210 in 2018, 2017 and 2016, respectively	10,484	10,153	9,612
Operating profit	20,002	24,227	23,480
Other (income) expense
Interest expense	243	241	246
Interest and other income, net	(1,809)	(957)	(384)
Total other (income) expense	(1,566)	(716)	(138)
Income before income tax expense (benefit)	21,568	24,943	23,618
Income tax expense (benefit)	1,883	(2,205)	5,864
Net income	$ 19,685	$ 27,148	$ 17,754
Net income per share of common stock
Basic (in dollars per share)	$ 3.52	$ 4.87	$ 3.19
Diluted (in dollars per share)	$ 3.51	$ 4.86	$ 3.19
Lime and limestone operations
Revenues
Total revenues	$ 141,922	$ 142,612	$ 137,190
Cost of revenues
Labor and other operating expenses	95,699	93,266	89,095
Natural gas interests
Revenues
Total revenues	2,513	2,232	2,092
Cost of revenues
Labor and other operating expenses	$ 859	$ 858	$ 1,164