Summary of Significant Accounting Policies - Additional Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Additions and write-offs to the company's allowance for doubtful accounts
Beginning balance	$ 430	$ 346
Additions	102	109
Write-offs	(171)	(25)
Ending balance	361	430	$ 346
Lime and limestone inventories:
Raw materials	4,546	4,693
Finished goods	1,954	2,153
Total	6,500	6,846
Service parts inventories	6,888	6,000
Total inventories	13,388	12,846
Supplemental cash flow information
Interest	150	179	140
Income taxes	445	331	6,718
Revenue Recognition
External freight billed to customers included in revenue	28,397	25,637	$ 23,489
Recurring | Fair value | Cash flows approach
Fair Values of Financial Instruments
Foreign exchange hedges liabilities	(1)	(16)
Recurring | Significant Other Observable Inputs (Level 2) | Fair value | Cash flows approach
Fair Values of Financial Instruments
Foreign exchange hedges liabilities	$ (1)	$ (16)