Business Segments (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)
Business segments
Number of business segments \| segment			2
Revenues	$ 35,272		$ 109,801
Depreciation, depletion and amortization	4,389	$ 4,240	12,854	$ 12,530
Gross profit (loss)	7,196	9,552	23,870	26,628
Capital expenditures	12,309	6,362	31,687	14,504
Lime and limestone operations
Business segments
Depreciation, depletion and amortization	4,234	4,048	12,375	11,935
Gross profit (loss)	6,992	9,476	23,112	26,218
Capital expenditures	12,309	6,362	31,687	14,502
Natural gas interests
Business segments
Depreciation, depletion and amortization	155	192	479	595
Gross profit (loss)	204	76	758	410
Capital expenditures				2
Lime and limestone operations \| Lime and limestone operations
Business segments
Revenues	34,713		107,984
Natural gas interests \| Natural gas interests
Business segments
Revenues	$ 559		$ 1,817
Before adoption of 606
Business segments
Revenues		36,934		109,605
Before adoption of 606 \| Lime and limestone operations \| Lime and limestone operations
Business segments
Revenues		36,428		107,910
Before adoption of 606 \| Natural gas interests \| Natural gas interests
Business segments
Revenues		$ 506		$ 1,695

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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