| Document and Entity Information | May 13, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | May 13, 2020 |
| Entity Registrant Name | JACK IN THE BOX INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-09390 |
| Entity Tax Identification Number | 95-2698708 |
| Entity Address, Address Line One | 9330 Balboa Avenue |
| Entity Address, City or Town | San Diego |
| Entity Address, State or Province | CA |
| Entity Address, Postal Zip Code | 92123 |
| City Area Code | 858 |
| Local Phone Number | 571-2121 |
| Entity Information, Former Legal or Registered Name | Not Applicable |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0000807882 |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | JACK |
| Security Exchange Name | NASDAQ |
