Business Segments (Details) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segment	Jun. 30, 2018 USD ($)
Business segments
Number of business segments \| segment			2
Revenues	$ 38,954	$ 39,242	$ 76,753	$ 74,529
Depreciation, depletion and amortization	4,225	4,288	8,293	8,465
Gross profit	9,727	9,637	18,420	16,674
Capital expenditures	6,676	5,333	12,360	19,378
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	4,089	4,129	8,018	8,141
Gross profit	9,690	9,327	18,376	16,120
Capital expenditures	6,676	5,333	12,360	19,378
Natural gas interests
Business segments
Depreciation, depletion and amortization	136	159	275	324
Gross profit	37	310	44	554
Lime and limestone operations
Business segments
Revenues	38,581	38,557	76,046	73,271
Lime and limestone operations \| Lime and limestone operations
Business segments
Revenues	38,581	38,557	76,046	73,271
Natural gas interests
Business segments
Revenues	373	685	707	1,258
Natural gas interests \| Natural gas interests
Business segments
Revenues	$ 373	$ 685	$ 707	$ 1,258

Amount of expense for allocation of cost of tangible and intangible assets over their useful lives, and reduction in quantity of natural resource due to consumption directly used in production of good and rendering of service.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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