Business Segments (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) segment	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business segments
Number of business segments | segment									2
Revenues	$ 34,166	$ 38,650	$ 32,880	$ 33,586	$ 31,294	$ 37,029	$ 32,450	$ 30,064	$ 139,282	$ 130,837	$ 149,841
Depreciation, depletion and amortization									15,931	15,784	14,706
Gross profit	7,434	$ 10,569	$ 7,241	$ 7,848	5,470	$ 10,367	$ 7,013	$ 5,864	33,092	28,714	36,791
Identifiable assets, at year end	210,159				196,499				210,159	196,499	199,986
Capital expenditures									17,664	11,459	15,377
Unallocated corporate assets and cash items
Business segments
Identifiable assets, at year end	76,376				62,256				76,376	62,256	61,263
Lime and limestone operations
Business segments
Revenues									137,190	128,390	144,567
Depreciation, depletion and amortization									15,063	14,910	13,811
Gross profit									33,032	28,400	33,958
Identifiable assets, at year end	126,015				125,703				126,015	125,703	128,961
Capital expenditures									17,649	11,444	15,352
Natural gas interests
Business segments
Revenues									2,092	2,447	5,274
Depreciation, depletion and amortization									868	874	895
Gross profit									60	314	2,833
Identifiable assets, at year end	$ 7,768				$ 8,540				7,768	8,540	9,762
Capital expenditures									$ 15	$ 15	$ 25