Business Segments (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($) segment	Mar. 31, 2018 USD ($)
Business segments
Number of business segments \| segment	2
Revenues	$ 37,799	$ 35,287
Depreciation, depletion and amortization	4,068	4,177
Gross profit	8,693	7,037
Capital expenditures	5,684	7,620
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	3,929	4,012
Gross profit	8,686	6,793
Capital expenditures	5,684	7,620
Natural gas interests
Business segments
Depreciation, depletion and amortization	139	165
Gross profit	7	244
Lime and limestone operations
Business segments
Revenues	37,465	34,714
Lime and limestone operations \| Lime and limestone operations
Business segments
Revenues	37,465	34,714
Natural gas interests
Business segments
Revenues	334	573
Natural gas interests \| Natural gas interests
Business segments
Revenues	$ 334	$ 573

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
-Topic 220
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-Section S99
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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 230
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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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