Business Segment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business segments
Number of business segments | segment	1
Revenues	$ 41,674	$ 38,440
Depreciation, depletion and amortization	5,276	4,601
Gross profit (loss)	11,805	9,877
Operating profit (loss)	8,738	6,658
Identifiable assets, at period end	285,410	251,867	$ 279,098
Capital expenditures	4,543	6,106
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	5,137	4,413
Gross profit (loss)	11,804	10,039
Operating profit (loss)	8,737	6,820
Identifiable assets, at period end	191,419	186,702
Capital expenditures	4,543	6,106
Other
Business segments
Depreciation, depletion and amortization	139	188
Gross profit (loss)	1	(162)
Operating profit (loss)	1	(162)
Identifiable assets, at period end	93,991	65,165
Lime and limestone operations | Lime and limestone operations
Business segments
Revenues	41,356	38,214
Natural gas interests | Other
Business segments
Revenues	$ 318	$ 226