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
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Use of Estimates
Change in Accounting Estimate Financial Effect Increase in Income from Continuing Operations before Income Taxes	$ 5	$ 18	$ 2	$ 57
Change in Accounting Estimate Financial Effect Increase in Income from Continuing Operations after Income Taxes	$ 3	$ 11	$ 1	$ 36
Change in Accounting Estimate Financial Effect Increase in Earnings Per Share Diluted	$ 0.01	$ 0.04	$ 0.00	$ 0.13
Gross Favorable Program Profit Adjustments	$ 20	$ 21	$ 63	$ 74
Gross Unfavorable Program Profit Adjustments	$ 15	$ 3	$ 61	$ 17