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		9 Months Ended
	Oct. 01, 2016	Oct. 03, 2015	Oct. 01, 2016	Oct. 03, 2015
Use of Estimates
Change in Accounting Estimate Financial Effect Increase in Income from Continuing Operations before Income Taxes	$ 18	$ 14	$ 57	$ 68
Change in Accounting Estimate Financial Effect Increase in Income from Continuing Operations after taxes	$ 11	$ 9	$ 36	$ 43
Change in Accounting Estimate Financial Effect Increase in Earnings Per Share Diluted	$ 0.04	$ 0.03	$ 0.13	$ 0.15
Gross Favorable Program Profit Adjustments	$ 21	$ 20	$ 74	$ 93
Gross Unfavorable Program Profit Adjustments	$ 3	$ 6	$ 17	$ 25