Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 28, 2019	Dec. 30, 2017	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Current [Abstract]
Federal			$ 4	$ 67	$ 7
State and local			346	790	473
Total current taxes			350	857	480
Deferred [Abstract]
Deferred	$ (496)	$ (1,086)	(496)	0	(1,086)
Provision for income taxes - current and deferred			$ (146)	$ 857	$ (606)