Components of Inventories (Detail) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Current inventory:
Raw materials	$ 35,610	$ 35,314
Work in process	8,555	8,131
Finished goods	10,279	9,054
Total current inventory	54,444	52,499
Long term inventory	9,170	6,316
Total inventory	$ 63,614	$ 58,815