Inventories - Schedule of Inventories (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 22,744	$ 18,314
Work-in-process	34,230	21,583
Finished goods	25,016	9,897
Supplies	11,988	9,940
Inventories	$ 93,978	$ 59,734