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. 31, 2017	Apr. 01, 2016
Accounting Policies [Abstract]
Net favorable impact to income from continuing operations before taxes	$ 22	$ 8
Increase in income from continuing operations per diluted share (usd per share)	$ 0.09	$ 0.07

Increase (Decrease) In Income From Change In Contract Estimates Per Diluted Share

No definition available.

Name:	ldos_IncreaseDecreaseInIncomeFromChangeInContractEstimatesPerDilutedShare
Namespace Prefix:	ldos_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration