Basis of Presentation - Contracts accounted for under percentage of completion method (Details) - Contracts accounted for under percentage of completion method - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2017	Jul. 02, 2016	Jul. 01, 2017	Jul. 02, 2016
Use of Estimates
Change in Accounting Estimate Financial Effect Increase (Decrease) in Income from Continuing Operations before Income Taxes	$ 9	$ 10	$ (3)	$ 39
Change in Accounting Estimate Financial Effect Increase (Decrease) in Income from Continuing Operations after Income Taxes	$ 6	$ 6	$ (2)	$ 25
Change in Accounting Estimate Financial Effect Increase (Decrease) in Earnings Per Share Diluted	$ 0.02	$ 0.02	$ (0.01)	$ 0.09
Gross Favorable Program Profit Adjustments	$ 23	$ 19	$ 43	$ 53
Gross Unfavorable Program Profit Adjustments	$ 14	$ 9	$ 46	$ 14