Summary of Significant Accounting Policies (Changes in Estimates on Contracts for the Periods Presented) (Details) - USD ($) $ / shares in Units, $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Jan. 03, 2025 |
Dec. 29, 2023 |
Dec. 30, 2022 |
|
| Accounting Policies [Abstract] | |||
| Favorable impact | $ 184 | $ 140 | $ 146 |
| Unfavorable impact | (153) | (100) | (113) |
| Net favorable impact to income before income taxes | $ 31 | $ 40 | $ 33 |
| Impact on diluted EPS attributable to Leidos common stockholders (usd per share) | $ 0.17 | $ 0.22 | $ 0.17 |