Income Taxes - Reconciliation of the Statutory Federal Income Tax Rate to the Company's Effective Income Tax Rate (Details)	12 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 29, 2018
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	24.50%
State income taxes, net of federal benefit	2.30%	4.30%	0.90%
Other permanent differences	0.00%	0.70%	(0.10%)
Adjustment of prior year accruals	(0.20%)	(0.60%)	0.00%
Credits	(0.60%)	(0.90%)	(0.80%)
Rate change – Tax reform	0.00%	0.00%	(16.90%)
Stock based compensation	(1.40%)	(1.60%)	(5.40%)
Other	(0.10%)	(0.60%)	0.40%
Effective income tax rate	21.00%	22.30%	2.60%