Acquisitions (Purchase price) (Details) - USD ($) $ in Millions	Aug. 16, 2016	Sep. 29, 2017	Dec. 30, 2016	Jan. 01, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill		$ 4,976	$ 4,622	$ 1,207
Information Systems & Global Solutions Business of Lockheed Martin
Business Combination, Consideration Transferred [Abstract]
Value of common stock issued to Lockheed Martin stockholders	$ 2,929
Equity consideration for replacement awards	9
Working capital adjustments	81
Purchase price	3,019
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash	25
Receivables	938
Inventory, prepaid expenses and other current assets	73
Property, plant and equipment	87
Intangible assets	1,194
Other assets	58
Accounts payable and accrued liabilities	(733)
Accrued payroll and employee benefits	(186)
Long-term debt, current portion	(23)
Deferred tax liabilities	(328)
Long-term debt, net of current portion	(1,780)
Other long-term liabilities	(45)
Total identifiable net liabilities assumed	(720)
Non-controlling interest	(13)
Goodwill	3,752
Purchase price	$ 3,019