Business Segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 segment	Dec. 31, 2011	Dec. 31, 2010
Business Segments
Number of business segments									2
Business segments
Revenues	$ 31,883	$ 34,116	$ 36,498	$ 36,028	$ 33,494	$ 39,182	$ 36,840	$ 33,066	$ 138,525	$ 142,582	$ 132,594
Depreciation, depletion and amortization									14,850	13,597	13,307
Gross profit	8,123	7,759	8,353	9,203	8,998	12,539	10,399	9,412	33,438	41,349	36,041
Identifiable assets, at year end	174,246				203,073				174,246	203,073	188,498
Capital expenditures									8,292	9,413	9,328
Lime and limestone operations
Business segments
Revenues									131,404	129,704	125,169
Depreciation, depletion and amortization									13,559	12,195	12,135
Gross profit									29,499	32,142	31,209
Identifiable assets, at year end	130,059				133,487				130,059	133,487	136,103
Capital expenditures									8,211	7,696	6,777
Natural gas interests
Business segments
Revenues									7,121	12,878	7,425
Depreciation, depletion and amortization									1,291	1,402	1,172
Gross profit									3,939	9,207	4,832
Identifiable assets, at year end	11,943				13,789				11,943	13,789	14,036
Capital expenditures									81	1,717	2,551
Unallocated corporate assets and cash items
Business segments
Identifiable assets, at year end	$ 32,244				$ 55,797				$ 32,244	$ 55,797	$ 38,359