| Document and Entity Information | Feb. 20, 2025 |
| Cover [Abstract] | |
| Amendment Flag | false |
| Entity Central Index Key | 0001336920 |
| Document Type | 8-K |
| Document Period End Date | Feb. 20, 2025 |
| Entity Registrant Name | LEIDOS HOLDINGS, INC. |
| Entity Incorporation State Country Code | DE |
| Entity File Number | 001-33072 |
| Entity Tax Identification Number | 20-3562868 |
| Entity Address, Address Line One | 1750 Presidents Street |
| 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 |
| Security 12b Title | Common stock, par value $.0001 per share |
| Trading Symbol | LDOS |
| Security Exchange Name | NYSE |
| Entity Emerging Growth Company | false |
