Nature Of Operations And Summary Of Significant Accounting Policies (Summary Of Number Of Restaurants) (Details) - restaurant	Oct. 01, 2017	Oct. 02, 2016	Sep. 27, 2015
Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	2,251	2,255	2,249
Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	726	699	661
Entity Operated Units [Member] | Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	276	417	413
Entity Operated Units [Member] | Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	385	367	322
Franchised Units [Member] | Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	1,975	1,838	1,836
Franchised Units [Member] | Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	341	332	339