Acquisitions (Textual) (Details) - Information Systems & Global Solutions Business of Lockheed Martin - USD ($) $ / shares in Units, shares in Millions, $ in Millions			3 Months Ended
	Aug. 16, 2016	Aug. 15, 2016	Mar. 31, 2017	Apr. 01, 2016
Business Acquisition [Line Items]
Number of shares Lockheed Martin shareholders will receive from Leidos (in shares)	77
Share price (in usd per share)	$ 51.69
Special dividend declared (usd per share)		$ 13.64
Decrease in PPE			$ (23)
Increase in other assets			81
Increase in accounts payable			19
Increase in accrued liabilities			13
Increase in deferred tax liabilities			$ 24
Fair value of non controlling interest	$ (8)
Goodwill acquired, expected tax deductible amount	$ 418
Acquisition related costs				$ 6
Acquired intangible assets, weighted average useful life (in years)	9 years
Intangible acquired, fair value	$ 1,650
Programs and contract intangibles
Business Acquisition [Line Items]
Acquired intangible assets, weighted average useful life (in years)	10 years
Intangible acquired, fair value	$ 1,450
Backlog
Business Acquisition [Line Items]
Acquired intangible assets, weighted average useful life (in years)	1 year 4 months 24 days
Intangible acquired, fair value	$ 200