Business Segment (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business segments
Number of business segments | segment			1
Revenues	$ 49,162	$ 37,547	$ 90,836	$ 75,987
Depreciation, depletion and amortization	5,234	4,796	10,575	9,453
Gross profit (loss)	16,795	10,357	28,600	20,234
Operating profit (loss)	13,838	7,476	22,576	14,134
Identifiable assets, at period end	297,112	259,270	297,112	259,270	$ 279,098
Capital expenditures	13,233	4,493	17,776	10,599
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	5,087	4,616	10,289	9,084
Gross profit (loss)	16,682	10,507	28,506	20,546
Operating profit (loss)	13,725	7,626	22,482	14,446
Identifiable assets, at period end	202,179	184,397	202,179	184,397
Capital expenditures	13,233	4,493	17,776	10,599
Other
Business segments
Depreciation, depletion and amortization	147	180	286	369
Gross profit (loss)	113	(150)	94	(312)
Operating profit (loss)	113	(150)	94	(312)
Identifiable assets, at period end	94,933	74,873	94,933	74,873
Lime and limestone operations | Lime and limestone operations
Business segments
Revenues	48,742	37,362	90,098	75,576
Natural gas interests | Other
Business segments
Revenues	$ 420	$ 185	$ 738	$ 411