Pretax Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 25, 2017	Jun. 26, 2016	Jun. 25, 2017	Jun. 26, 2016
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 205	$ 204	$ 410	$ 407
Interest cost	453	466	905	931
Expected return on plan assets	(602)	(666)	(1,204)	(1,333)
Recognized net actuarial losses	377	339	753	679
Amortization of prior service costs	(90)	(92)	(176)	(182)
Total net periodic benefit cost	343	251	688	502
Retiree medical and life insurance plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	6	10	12
Interest cost	25	29	51	59
Expected return on plan assets	(32)	(35)	(64)	(69)
Recognized net actuarial losses	5	9	10	17
Amortization of prior service costs	4	6	7	11
Total net periodic benefit cost	$ 7	$ 15	$ 14	$ 30