Postretirement Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 25, 2016	Sep. 27, 2015	Sep. 25, 2016	Sep. 27, 2015
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, net of tax	$ 175	$ 212	$ 521	$ 637
Recognition of previously deferred postretirement benefit plan amounts, tax	96	117	285	349
Other postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, before tax	11	16	32	44
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Contributions made by the employer	$ 0	$ 0	$ 0	$ 0