Basis of Presentation and Summary of Significant Accounting Policies (Changes in Estimates on Contracts) (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 27, 2024 |
Sep. 29, 2023 |
Sep. 27, 2024 |
Sep. 29, 2023 |
|
| Accounting Policies [Abstract] | ||||
| Favorable impact | $ 58 | $ 40 | $ 125 | $ 102 |
| Unfavorable impact | (28) | (24) | (107) | (62) |
| Net impact to income before income taxes | $ 30 | $ 16 | $ 18 | $ 40 |
| Impact on diluted EPS attributable to Leidos common stockholders (in dollars per share) | $ 0.17 | $ 0.09 | $ 0.10 | $ 0.22 |