Acquisitions (Purchase price) (Details) - USD ($) $ in Millions	Aug. 16, 2016	Mar. 31, 2017	Dec. 30, 2016	Jan. 01, 2016
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill		$ 4,619	$ 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(1)	$ 2,929
Equity consideration for replacement awards	9
Preliminary working capital adjustments	56
Preliminary purchase price	2,994
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Cash	25
Receivables	943
Inventory, prepaid expenses and other current assets	73
Property, plant and equipment	114
Deferred tax assets	12
Intangible assets	1,650
Other assets	104
Accounts payable	(286)
Accrued liabilities	(446)
Accrued payroll and employee benefits	(190)
Long-term debt, current portion	(23)
Deferred tax liabilities	(556)
Long-term debt, net of current portion	(1,780)
Other long-term liabilities	(50)
Total identifiable net liabilities assumed	(410)
Non-controlling interest	(8)
Goodwill	3,412
Preliminary purchase price	$ 2,994