Summary of Significant Accounting Policies - Supplemental Cash Flow Items (Details) - USD ($) $ in Thousands	6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016
Supplemental Disclosures of Cash Flow Information
Interest paid	$ 3,102	$ 3,741
Taxes paid	685	2,479
Non-cash activities:
Purchases of property and equipment not paid	$ 2,878	$ 1,278