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Inventories - Schedule of Inventories (Detail) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Inventory [Line Items]    
Total inventory $ 13,571 $ 18,575
Sand    
Inventory [Line Items]    
Raw material 978 1,201
Work in progress 8,401 10,070
Finished goods 3,047 4,648
Spare parts 1,145 1,356
Total inventory $ 13,571 $ 17,275