Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Lime and limestone operations	$ 142,612	$ 137,190	$ 128,390
Natural gas interests	2,232	2,092	2,447
Total revenues	144,844	139,282	130,837
Labor and other operating expenses
Lime and limestone operations	93,266	89,095	85,080
Natural gas interests	858	1,164	1,259
Depreciation, depletion and amortization	16,340	15,931	15,784
Total cost of revenues	110,464	106,190	102,123
Gross profit	34,380	33,092	28,714
Selling, general and administrative expenses, including depreciation and amortization expense of $209, $210 and $249 in 2017, 2016 and 2015, respectively	10,153	9,612	9,628
Operating profit	24,227	23,480	19,086
Other (income) expenses
Interest expense	241	246	1,036
Interest and other (income) expense, net	(957)	(384)	569
Total other expense (income)	(716)	(138)	1,605
Income before income tax (benefit) expense	24,943	23,618	17,481
Income tax (benefit) expense	(2,205)	5,864	4,595
Net income	$ 27,148	$ 17,754	$ 12,886
Net income per share of common stock
Basic (in dollars per share)	$ 4.87	$ 3.19	$ 2.30
Diluted (in dollars per share)	4.86	3.19	2.30
Cash dividends per share of common stock (in dollars per share)	$ 0.54	$ 0.50	$ 0.50