Summary of Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue Recognition
Revenues	$ 37,965	$ 43,559	$ 38,954	$ 37,799	$ 34,634	$ 35,272	$ 39,242	$ 35,287	$ 158,277	$ 144,435	$ 144,844
Gross profit
Gross profit (loss), Lime and limestone operations	10,190	13,477	9,690	8,686	6,370	6,992	9,327	6,793
Gross profit (loss), other	(417)	6	37	7	246	204	310	244
Gross profit	9,773	13,483	9,727	8,693	6,616	7,196	9,637	7,037	41,676	30,486	34,380
Net income	$ 4,993	$ 9,902	$ 6,033	$ 5,128	$ 4,231	$ 4,554	$ 6,638	$ 4,262	$ 26,056	$ 19,685	$ 27,148
Basic income per common share (in dollars per share)	$ 0.89	$ 1.76	$ 1.07	$ 0.91	$ 0.76	$ 0.81	$ 1.19	$ 0.76	$ 4.64	$ 3.52	$ 4.87
Diluted income per common share (in dollars per share)	$ 0.89	$ 1.76	$ 1.07	$ 0.91	$ 0.75	$ 0.81	$ 1.18	$ 0.76	$ 4.64	$ 3.51	$ 4.86
Lime and limestone operations
Revenue Recognition
Revenues	$ 37,670	$ 43,265	$ 38,581	$ 37,465	$ 33,938	$ 34,713	$ 38,557	$ 34,714
Other
Revenue Recognition
Revenues	$ 295	$ 294	$ 373	$ 334	$ 696	$ 559	$ 685	$ 573