Pretax Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 26, 2017	Mar. 27, 2016
Qualified defined benefit pension plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 205	$ 203
Interest cost	452	465
Expected return on plan assets	(602)	(667)
Recognized net actuarial losses	376	340
Amortization of net prior service costs	(86)	(90)
Total net periodic benefit cost	345	251
Retiree medical and life insurance plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	6
Interest cost	26	30
Expected return on plan assets	(32)	(34)
Recognized net actuarial losses	5	8
Amortization of net prior service costs	3	5
Total net periodic benefit cost	$ 7	$ 15