Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Principles of Consolidation and Reclassifications
Reclassification of amount from deferred income taxes to prepaid expenses and other current assets		$ 515
Supplemental cash flow information
Interest	2,069	2,395	2,681
Income taxes	3,000	4,529	3,956
Revenue Recognition
External freight billed to customer included in revenue	26,675	26,470	25,756
Additions and write-offs to the company's allowance for doubtful accounts
Beginning balance	429	360
Additions	105	91
Write-offs	(9)	(22)
Ending balance	525	429	360
Lime and limestone inventories:
Raw materials	6,718	3,540
Finished goods	2,328	2,107
Total	9,046	5,647
Service parts inventories	5,081	5,117
Total inventories	14,127	10,764
Recurring | Fair value | Cash flows approach
Fair Values of Financial Instruments
Interest rate swap liabilities	(2,629)	(3,486)
Recurring | Significant Other Observable Inputs (Level 2) | Cash flows approach
Fair Values of Financial Instruments
Interest rate swap liabilities	$ (2,629)	$ (3,486)