Postretirement Benefit Plans - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 26, 2016	Jun. 28, 2015	Jun. 26, 2016	Jun. 28, 2015
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, net of tax	$ 173,000,000	$ 213,000,000	$ 346,000,000	$ 425,000,000
Recognition of previously deferred postretirement benefit plan amounts, tax	94,000,000	116,000,000	189,000,000	232,000,000
Other postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, before tax	10,000,000	$ 15,000,000	$ 21,000,000	28,000,000
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Contributions made by the employer	$ 0			$ 0