Inventories (Detail) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw material		$ 1,515	$ 1,649
Work-in-process		8,757	7,963
Finished goods	[1]	5,198	5,132
Supplies		686	723
Total inventories		$ 16,156	$ 15,467

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