Revenue - Impact of Adjustments in Contract Estimates (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating earnings	$ 1,088	$ 1,067	$ 2,096	$ 2,113
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue	91	90	206	162
Operating earnings	$ 83	$ 121	$ 180	$ 171
Diluted earnings per share	$ 0.22	$ 0.26	$ 0.47	$ 0.36