Postretirement Plans - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 26, 2017	Mar. 27, 2016
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, net of tax	$ 202,000,000	$ 173,000,000
Recognition of previously deferred postretirement benefit plan amounts, tax	110,000,000	95,000,000
Other postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Recognition of previously deferred postretirement benefit plan amounts, before tax	14,000,000	11,000,000
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Contributions made by the employer	$ 0	$ 0