Summary of Refranchisings, Franchisee Development and Acquisitions (Number of Restaurants Sold to Franchisees and Developed by Franchisees and Gains Recognized) (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Apr. 12, 2020 USD ($) restaurant	Sep. 27, 2020 USD ($) restaurant	Sep. 29, 2019 USD ($) restaurant	Sep. 30, 2018 USD ($) restaurant
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Restaurants sold to franchisees | restaurant		0	0	135
Cash		$ 3,395	$ 1,280	$ 26,486
Total proceeds from the sale of company-operated restaurants		3,395	1,280	96,947
Net assets sold (primarily property and equipment)		0	0	(21,329)
Goodwill related to the sale of company-operated restaurants		0	(2)	(4,663)
Other		(134)	88	(24,791)
Gains on the sale of company-operated restaurants		3,261	1,366	46,164
Additional proceeds from the sale of a company-operated restaurant		3,400	1,300	$ 1,400
Maintenance and repair expenses			2,300
Other miscellaneous non-capital charges			$ 3,700
Number of restaurants acquired from franchisees | restaurant			0	0
Franchise Acquisitions
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Consideration transferred	$ 900
Obtained Judgment
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Number of restaurants acquired from franchisees | restaurant	8
2017 Reacquired Franchise Restaurants
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Reduction of gains related to modification			$ 8,700
Franchise Remodel Incentive
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Costs related to franchise remodel incentives			9,200
Notes Receivable
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Notes receivable		$ 0	$ 0	$ 70,461