Summary of Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue Recognition
Revenues	$ 40,990	$ 43,727	$ 37,547	$ 38,440	$ 37,965	$ 43,559	$ 38,954	$ 37,799	$ 160,704	$ 158,277	$ 144,435
Gross profit
Gross profit (loss), Lime and limestone operations	13,181	14,256	10,507	10,039	10,190	13,477	9,690	8,686
Gross profit (loss), other	(10)	(74)	(150)	(162)	(417)	6	37	7
Gross profit (loss)	13,171	14,182	10,357	9,877	9,773	13,483	9,727	8,693	47,587	41,676	30,486
Net income	$ 7,254	$ 9,324	$ 6,101	$ 5,544	$ 4,993	$ 9,902	$ 6,033	$ 5,128	$ 28,223	$ 26,056	$ 19,685
Basic income per common share (in dollars per share)	$ 1.29	$ 1.66	$ 1.08	$ 0.99	$ 0.89	$ 1.76	$ 1.07	$ 0.91	$ 5.01	$ 4.64	$ 3.52
Diluted income per common share (in dollars per share)	$ 1.28	$ 1.65	$ 1.08	$ 0.98	$ 0.89	$ 1.76	$ 1.07	$ 0.91	$ 5.00	$ 4.64	$ 3.51
Lime and limestone operations
Revenue Recognition
Revenues	$ 40,658	$ 43,473	$ 37,362	$ 38,214	$ 37,670	$ 43,265	$ 38,581	$ 37,465
Other
Revenue Recognition
Revenues	$ 332	$ 254	$ 185	$ 226	$ 295	$ 294	$ 373	$ 334