Business Segment (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Business segments
Number of business segments | segment	1
Revenues	$ 38,440	$ 37,799
Depreciation, depletion and amortization	4,601	4,068
Gross profit (loss)	9,877	8,693
Operating profit (loss)	6,658	6,020
Identifiable assets, at period end	251,867	255,069	$ 247,037
Capital expenditures	6,106	5,684
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	4,413	3,929
Gross profit (loss)	10,039	8,686
Operating profit (loss)	6,820	6,013
Identifiable assets, at period end	186,702	178,346
Capital expenditures	6,106	5,684
Other
Business segments
Depreciation, depletion and amortization	188	139
Gross profit (loss)	(162)	7
Operating profit (loss)	(162)	7
Identifiable assets, at period end	65,165	76,723
Lime and limestone operations | Lime and limestone operations
Business segments
Revenues	38,214	37,465
Natural gas interests | Other
Business segments
Revenues	$ 226	$ 334