Inventories, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Lime and limestone inventories:
Raw materials	$ 4,628	$ 5,105
Finished goods	1,851	2,266
Total	6,479	7,371
Service parts inventories	6,120	6,175
Total inventories	$ 12,599	$ 13,546