Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes
Current income tax expense	$ 3,547	$ 4,398	$ 3,945
Deferred income taxes	2,131	3,560	3,073
Income tax expense	5,678	7,958	7,018
Amount
Income taxes computed at the federal statutory rate	7,735	10,550	8,770
(Reduction) increase in taxes resulting from:
Statutory depletion in excess of cost depletion	(2,048)	(2,366)	(1,584)
Manufacturing deduction	(335)	(308)	(397)
State income taxes, net of federal income tax benefit	331	24	155
Other	(5)	58	74
Income tax expense	5,678	7,958	7,018
Percent of pretax income
Income taxes computed at the federal statutory rate (as a percent)	35.00%	35.00%	35.00%
(Reduction) increase in taxes resulting from (as a percent):
Statutory depletion in excess of cost depletion (as a percent)	(9.30%)	(7.90%)	(6.30%)
Manufacturing deduction (as a percent)	(1.50%)	(1.00%)	(1.60%)
State income taxes, net of federal income tax benefit (as a percent)	1.50%	0.10%	0.60%
Other (as a percent)	0.00%	0.20%	0.30%
Income tax expense (as a percent)	25.70%	26.40%	28.00%
Deferred tax liabilities
Lime and limestone property, plant and equipment	19,306	17,625
Natural gas interests drilling costs and equipment	3,952	4,247
Other	344	316
Total	23,602	22,188
Deferred tax assets
Alternative minimum tax credit carry forwards	6,489	7,364
Minimum pension liability	412	448
Fair value liability of interest rate hedges	956	1,268
Other	769	611
Total	8,626	9,691
Net deferred tax liabilities	14,976	12,497
Current income taxes:
Accrued expense	307
Prepaid expenses and other current assets		241
Deferred income taxes:
Prepaid expenses and other current assets	678	515
Deferred tax liabilities, net	$ 15,654	$ 13,012