| Cover | Jan. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Jan. 12, 2021 |
| Entity Registrant Name | Del Taco Restaurants, Inc. |
| Entity Emerging Growth Company | false |
| Entity File Number | 001-36197 |
| Soliciting Material | false |
| Written Communications | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Amendment Flag | false |
| Entity Central Index Key | 0001585583 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 46-3340980 |
| Entity Address, Postal Zip Code | 92630 |
| Entity Address, State or Province | CA |
| Entity Address, City or Town | Lake Forest, |
| Entity Address, Address Line One | 25521 Commercentre Drive |
| Local Phone Number | 462-9300 |
| City Area Code | (949) |
| Title of 12(b) Security | Common Stock, $0.001 par value per share |
| Trading Symbol | TACO |
| Security Exchange Name | NASDAQ |
