Summary of Significant Accounting Policies - Reconciliation of Changes in Deferred Revenue (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 29, 2019	Jun. 30, 2018	Dec. 29, 2018	[1]
Reconciliation of the changes in the Company's deferred revenue balance
Balance, beginning of period	$ 2,225	$ 2,520
Additions to deferral	985	789
Revenue recognized	(1,227)	(993)
Balance, end of period	1,983	2,316
Non-current portion of deferred revenue	469	633	$ 586
Current portion of deferred revenue	$ 1,514	$ 1,683	$ 1,639

[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 29, 2018.