Nature Of Operations And Summary Of Significant Accounting Policies (Summary Of Number Of Restaurants) (Details) - restaurant	Sep. 27, 2015	Sep. 28, 2014	Sep. 29, 2013
Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	2,249	2,250	2,251
Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	661	638	615
Company-Operated [Member] | Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	413	431	465
Company-Operated [Member] | Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	322	310	296
Franchise [Member] | Jack in the box brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	1,836	1,819	1,786
Franchise [Member] | Qdoba brand restaurant operations [Member]
Nature Of Operations And Summary Of Significant Accounting Policies [Line Items]
Number of Restaurants	339	328	319