Basis of Presentation and Summary of Significant Accounting Policies (Changes in Estimates on Contracts) (Details) - USD ($) $ / shares in Units, $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 29, 2024 |
Mar. 31, 2023 |
|
| Accounting Policies [Abstract] | ||
| Favorable impact | $ 25 | $ 22 |
| Unfavorable impact | (25) | (16) |
| Net impact to income before income taxes | $ 0 | $ 6 |
| Impact on diluted EPS attributable to Leidos common stockholders (in dollars per share) | $ 0 | $ 0.03 |