Business Segment (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business segments
Number of business segments | segment			1
Revenues	$ 52,311	$ 43,727	$ 143,147	$ 119,714
Depreciation, depletion and amortization	4,989	4,880	15,432	14,224
Gross profit (loss)	17,341	14,182	45,941	34,416
Operating profit (loss)	14,196	11,273	36,772	25,407
Identifiable assets, at period end	310,908	271,707	310,908	271,707	$ 279,098
Capital expenditures	5,955	3,022	23,731	13,621
Lime and Limestone Operations Segment Member
Business segments
Depreciation, depletion and amortization	4,844	4,706	15,002	13,681
Gross profit (loss)	17,128	14,256	45,634	34,802
Operating profit (loss)	13,983	11,347	36,465	25,793
Identifiable assets, at period end	204,841	194,819	204,841	194,819
Capital expenditures	5,955	3,022	23,731	13,621
Other
Business segments
Depreciation, depletion and amortization	145	174	430	543
Gross profit (loss)	213	(74)	307	(386)
Operating profit (loss)	213	(74)	307	(386)
Identifiable assets, at period end	106,067	76,888	106,067	76,888
Lime and limestone operations | Lime and Limestone Operations Segment Member
Business segments
Revenues	51,749	43,473	141,847	119,049
Natural gas interests | Other
Business segments
Revenues	$ 562	$ 254	$ 1,300	$ 665