Supplemental Disclosures to Condensed Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jul. 03, 2018	Jul. 04, 2017
Class of Stock [Line Items]
Interest paid (net of amounts capitalized)	$ 1,973	$ 2,216
Income taxes paid (refunded)	49	(60)
Changes in purchases of property and equipment accrued in accounts payable, net	1,580	1,417
Common Stock | Common Class A
Class of Stock [Line Items]
Conversion of Series A convertible preferred stock to common stock	$ 0	$ 18,500