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Inventories - Summary of Inventories (Detail) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Inventory Disclosure [Abstract]    
Finished goods $ 39,788 $ 32,986
Raw materials 20,801 19,432
Total FIFO (first-in,first-out) inventories 60,589 52,418
Reserve to adjust inventories to LIFO value (20,070) (20,070)
Total LIFO inventories $ 40,519 $ 32,348