Basis of Presentation - Additional Information (Details) - USD ($) $ in Thousands	Sep. 26, 2020	Dec. 28, 2019	[1]	Dec. 26, 2019	Sep. 28, 2019	Dec. 28, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents	$ 11,932			$ 12,653	$ 12,948	$ 21,194
Accumulated deficit	$ 56,765	$ 50,615

[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.