Summary of Quarterly Financial Data (unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues
Lime and limestone operations	$ 28,666	$ 35,498	$ 33,684	$ 30,155	$ 30,212	$ 32,558	$ 34,729	$ 33,905	$ 128,003	$ 131,404	$ 129,704
Natural gas interests	1,443	1,401	1,488	1,430	1,671	1,558	1,769	2,123	5,762	7,121	12,878
Revenues	30,109	36,899	35,172	31,585	31,883	34,116	36,498	36,028	133,765	138,525	142,582
Gross profit
Gross profit, Lime and limestone operations	5,474	8,409	8,363	5,667	7,252	6,972	7,324	7,951
Gross profit, Natural gas interests	961	701	601	624	871	787	1,029	1,252
Gross profit	6,435	9,110	8,964	6,291	8,123	7,759	8,353	9,203	30,800	33,438	41,349
Net income	$ 2,629	$ 4,789	$ 4,626	$ 2,757	$ 3,792	$ 3,947	$ 4,060	$ 4,624	$ 14,800	$ 16,423	$ 22,186
Basic income per common share (in dollars per share)	$ 0.47	$ 0.86	$ 0.83	$ 0.50	$ 0.68	$ 0.71	$ 0.73	$ 0.75	$ 2.66	$ 2.88	$ 3.50
Diluted income per common share (in dollars per share)	$ 0.47	$ 0.86	$ 0.83	$ 0.50	$ 0.68	$ 0.71	$ 0.73	$ 0.75	$ 2.66	$ 2.87	$ 3.49