Changes in Balance of Accumulated Other Comprehensive Loss, Net of Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 26, 2017		Mar. 27, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 1,606		$ 3,097
Other comprehensive income before reclassifications	7		15
Amounts reclassified from AOCL
Recognition of net actuarial losses	258	[1]	234
Amortization of net prior service credits	(56)	[1]	(61)
Other	1		2
Total reclassified from AOCL	203		175
Other comprehensive income, net of tax	210		190
Ending Balance	1,585		3,177
Postretirement Benefit Plan Adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(11,981)		(11,314)
Other comprehensive income before reclassifications	3
Amounts reclassified from AOCL
Recognition of net actuarial losses	258	[1]	234
Amortization of net prior service credits	(56)	[1]	(61)
Total reclassified from AOCL	202		173
Other comprehensive income, net of tax	205		173
Ending Balance	(11,776)		(11,141)
Other, net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(121)		(130)
Other comprehensive income before reclassifications	4		15
Amounts reclassified from AOCL
Other	1		2
Total reclassified from AOCL	1		2
Other comprehensive income, net of tax	5		17
Ending Balance	(116)		(113)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(12,102)		(11,444)
Amounts reclassified from AOCL
Other comprehensive income, net of tax	210		190
Ending Balance	$ (11,892)		$ (11,254)

[1] Reclassifications from AOCL related to our postretirement benefit plans were recorded as a component of net periodic benefit cost for each period presented (see "Note 6 - Postretirement Plans").