Acquisitions (Details) - Lockheed Martin Merger shares in Millions, $ in Millions	Jan. 26, 2016 USD ($) shares
Business Acquisition [Line Items]
Number of shares Lockheed Martin shareholders will receive from Leidos, as a percentage of Leidos common stock (in percentage)	50.50%
Percentage of common stock retained by the Leidos ( in percentage)	49.50%
Accrued dividends declared	$ 1,030.0
Termination fees	150.0
Reimbursement of expense, if termination of merger is due to rejection from shareholders'	37.5
Splitco
Business Acquisition [Line Items]
Debt financing	1,800.0
Payments to parent, special payment	$ 1,800.0
Lockheed Martin Shareholders'
Business Acquisition [Line Items]
Number of shares Lockheed Martin shareholders will receive from Leidos (in shares) | shares	77
Term Loan
Business Acquisition [Line Items]
Long-term debt, expected	$ 2,500.0
Line of Credit | Revolving Credit Facility
Business Acquisition [Line Items]
Maximum borrowing capacity	$ 750.0