Summary of Significant Accounting Policies - Supplemental Cash Flow Items (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016
Supplemental Disclosures of Cash Flow Information
Interest paid	$ 4,867	$ 5,283
Taxes paid	1,969	5,539
Non-cash activities:
Purchases of property and equipment not paid	$ 890	$ 687