Summary of Significant Accounting Policies - Additional Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Values of Financial Instruments
Foreign exchange hedges liabilities	$ (16)
Foreign exchange hedges assets		$ 111
Additions and write-offs to the company's allowance for doubtful accounts
Beginning balance	346	334
Additions	109	69
Write-offs	(25)	(57)
Ending balance	430	346	$ 334
Lime and limestone inventories:
Raw materials	4,693	5,105
Finished goods	2,153	2,266
Total	6,846	7,371
Service parts inventories	6,000	6,175
Total inventories	12,846	13,546
Supplemental cash flow information
Interest	179	140	113
Income taxes	331	6,718	4,908
Revenue Recognition
External freight billed to customers included in revenue	25,637	23,489	$ 23,087
Recurring | Fair value | Cash flows approach
Fair Values of Financial Instruments
Foreign exchange hedges liabilities	(16)
Foreign exchange hedges assets		111
Recurring | Significant Other Observable Inputs (Level 2) | Fair value | Cash flows approach
Fair Values of Financial Instruments
Foreign exchange hedges liabilities	$ (16)
Foreign exchange hedges assets		$ 111