Inventories (Details) - USD ($) $ in Thousands	Oct. 01, 2017	Jan. 01, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 178,666	$ 165,896
Finished goods	80,989	65,791
Provision for obsolete or aged inventory	(7,550)	(5,747)
Inventories, net	$ 252,105	$ 225,940