| Cover Page | Jan. 31, 2020 |
| Cover page. | |
| Document Type | 8-K |
| Document Period End Date | Jan. 31, 2020 |
| Entity Registrant Name | LEIDOS HOLDINGS, INC. |
| Entity Central Index Key | 0001336920 |
| Amendment Flag | false |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-33072 |
| Entity Tax Identification Number | 20-3562868 |
| Entity Address, Address Line One | 11951 Freedom Drive |
| Entity Address, City or Town | Reston |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 20190 |
| City Area Code | 571 |
| Local Phone Number | 526-6000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock, par value $.0001 per share |
| Trading Symbol | LDOS |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
