Business Segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) segment	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Segments
Number of business segments | segment									2
Business segments
Revenues	$ 31,294	$ 37,029	$ 32,450	$ 30,064	$ 35,401	$ 39,073	$ 38,676	$ 36,691	$ 130,837	$ 149,841	$ 133,765
Depreciation, depletion and amortization									15,784	14,706	14,291
Gross profit	5,470	$ 10,367	$ 7,013	$ 5,864	7,893	$ 9,883	$ 10,423	$ 8,592	28,714	36,791	30,800
Identifiable assets, at year end	196,499				199,986				196,499	199,986	187,526
Capital expenditures									11,459	15,377	8,921
Unallocated corporate assets and cash items
Business segments
Identifiable assets, at year end	62,256				61,263				62,256	61,263	51,777
Lime and limestone operations
Business segments
Revenues									128,390	144,567	128,003
Depreciation, depletion and amortization									14,910	13,811	13,336
Gross profit									28,400	33,958	27,913
Identifiable assets, at year end	125,703				128,961				125,703	128,961	124,839
Capital expenditures									11,444	15,352	8,863
Natural gas interests
Business segments
Revenues									2,447	5,274	5,762
Depreciation, depletion and amortization									874	895	955
Gross profit									314	2,833	2,887
Identifiable assets, at year end	$ 8,540				$ 9,762				8,540	9,762	10,910
Capital expenditures									$ 15	$ 25	$ 58