Summary of Significant Accounting Policies - Reconciliation of Changes in Deferred Revenue (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2020	Sep. 28, 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	1,067	1,580
Revenue recognized	(1,516)	(1,892)
Deductions from reserves	(3)	(19)
Balance, end of period	1,358	1,894
Non-current portion of deferred revenue	286	366	$ 360
Current portion of deferred revenue	$ 1,072	$ 1,528	$ 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.