Summary Of Refranchisings, Franchisee Development And Acquisitions (Purchase Price Allocations On Franchise Acquisitions) (Details) $ in Thousands	4 Months Ended	12 Months Ended
	Jan. 21, 2018 USD ($)	Oct. 01, 2017 USD ($) restaurant	Oct. 02, 2016 USD ($) restaurant	Sep. 27, 2015 USD ($) restaurant
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Restaurants acquired from franchisees (restaurants) | restaurant			15
Goodwill, Acquired During Period		$ 13,059	$ 17,034
Property and equipment			2,954
Noncash or Part Noncash Acquisition, Intangible Assets Acquired			91
Noncash or Part Noncash Acquisition, Inventory Acquired			0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed			(114)
Business Combination, Bargain Purchase, Gain Recognized, Amount			(289)
Other			140
Business Combination, Consideration Transferred			$ 19,816
Jack in the box brand restaurant operations [Member]
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Restaurants acquired from franchisees (restaurants) | restaurant		50	1	7
Goodwill, Acquired During Period		$ 13,059	$ 0	$ 0
Property and equipment		2,470		646
Noncash or Part Noncash Acquisition, Intangible Assets Acquired		1,260		0
Noncash or Part Noncash Acquisition, Inventory Acquired		189		0
Noncash or Part Noncash Acquisition, Value of Liabilities Assumed		(1,116)		(613)
Business Combination, Bargain Purchase, Gain Recognized, Amount	$ 0			(33)
Other		0		0
Business Combination, Consideration Transferred		15,862		$ 0
Noncash or Part Noncash Divestiture, Amount of Consideration Received		13,800
Noncash or Part Noncash Acquisition, Payables Assumed		3,900
Jack in the box brand restaurant operations [Member] | Accounts Receivable [Member]
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Noncash or Part Noncash Divestiture, Amount of Consideration Received		9,900
Qdoba brand restaurant operations [Member]
Summary Of Refranchisings, Franchisee Development And Acquisitions [Line Items]
Restaurants acquired from franchisees (restaurants) | restaurant			14
Goodwill, Acquired During Period		$ 0	$ 17,034