Postretirement Benefit Plans - Additional Information (Details) - U.S. - USD ($)	3 Months Ended			12 Months Ended
	Sep. 28, 2018	Mar. 30, 2018	Sep. 29, 2017	Jun. 30, 2017	Jun. 29, 2018	Dec. 31, 2016
Pension
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined benefit plan, voluntary contributions by employer during period	$ 0	$ 300,000,000	$ 0	$ 400,000,000
Defined benefit plans, estimated future employer contributions in current fiscal year	$ 0
U.S. SRP
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Value of defined benefit pension plan assets					$ 4,600,000,000
Projected benefit obligation of defined pension plan					$ 5,200,000,000
Cash balance percentage to replace frozen benefits under defined pension plan						1.00%