Summary of Significant Accounting Policies - ASU 2014-09 (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 30, 2017	Dec. 31, 2016
New Accounting Standards
Retained earnings		$ 5,368	$ 5,546
Inventory		$ 4,150	$ 4,464
Cumulative effect transition adjustment | Accounting Standards Update 2014-09
New Accounting Standards
Retained earnings	$ 90
Contract assets	350
Inventory	$ (200)
Cumulative effect transition adjustment | Accounting Standards Update 2014-09 | Bell
New Accounting Standards
Percentage of increase (decrease) in backlog for segments	(15.00%)
Cumulative effect transition adjustment | Accounting Standards Update 2014-09 | Textron Systems
New Accounting Standards
Percentage of increase (decrease) in backlog for segments	7.00%