Nature of Operations and Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands	1 Months Ended		3 Months Ended	12 Months Ended
	Apr. 30, 2020	Mar. 31, 2020	Dec. 31, 2020	Sep. 27, 2020 USD ($) restaurant	Sep. 29, 2019 USD ($) restaurant	Sep. 30, 2018 USD ($) restaurant	Sep. 30, 2019 USD ($)
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of restaurants | restaurant				2,241	2,243	2,237
Number of weeks per fiscal year				52	52	52
Business outside of dining rooms (percentage)				90.00%
Depreciation				$ 52,800	$ 55,200	$ 59,400
Intangible assets, carrying value				277	425		$ 39
Amounts recognized on unredeemed gift card balances				500	500	600
General liability and workers' comp estimated claims to be paid by insurance providers				$ 1,900	3,600
Contractual contributions		4.00%		5.00%
Collection period for marketing fees		24 months
Uncollected postponed marketing fees				$ 16,100
Accrued advertising costs				8,300	300
Incremental corporate advertising contributions				0	2,000	6,200
Marketing and advertising expense				17,100	19,000	$ 28,800
Deferred tax assets				72,322	85,564		$ 86,570
Other Assets
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Cash surrender value of life insurance				113,800	$ 112,800
Uncollected postponed marketing fees				3,500
Accounts Receivable
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Uncollected postponed marketing fees				$ 12,600
Forecast
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Collection period for marketing fees			3 months
Minimum
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment assigned lives				1 year
Contractual contributions	2.00%
Maximum
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment assigned lives				35 years
Contractual contributions	4.00%