Summary of Significant Accounting Policies - Reconciliation of Changes in Deferred Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 27, 2020	Jun. 29, 2019	Dec. 28, 2019	[1]
Reconciliation of the changes in the Company's deferred revenue balance
Balance, beginning of period	$ 1,810	$ 2,225
Additions to deferral	743	990
Revenue recognized	(1,023)	(1,232)
Deductions from reserves	(6)
Balance, end of period	1,524	1,983
Non-current portion of deferred revenue	302	469	$ 360
Current portion of deferred revenue	$ 1,222	$ 1,514	$ 1,450

[1] Derived from the audited consolidated financial statements included in the Annual Report on Form 10-K filed with the SEC for the year ended December 28, 2019.