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. 30, 2022 |
Oct. 01, 2021 |
Sep. 30, 2022 |
Oct. 01, 2021 |
|
| Accounting Policies [Abstract] | ||||
| Favorable impact | $ 36 | $ 47 | $ 116 | $ 115 |
| Unfavorable impact | (29) | (24) | (75) | (72) |
| Net impact to income before income taxes | $ 7 | $ 23 | $ 41 | $ 43 |
| Impact on diluted EPS attributable to Leidos common stockholders (dollars per share) | $ 0.03 | $ 0.12 | $ 0.22 | $ 0.22 |