Change in Benefit Obligations (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Pension Plans, Defined Benefit
Benefit obligation, beginning of year	$ 2,838	[1]	$ 2,661
Defined Benefit Plan, Interest Cost	113		119		128
Defined Benefit Plan, Contributions by Plan Participants	0		0
Defined Benefit Plan, Actuarial Gain (Loss)	(195)		242
Defined Benefit Plan, Benefits Paid	(181)		(184)
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	0		0
Defined Benefit Plan, Plan Amendments	0		0
Benefit obligation, end of year	2,575	[1]	2,838	[1]	2,661
Other Postretirement Benefit Plans, Defined Benefit
Benefit obligation, beginning of year	167	[1],[2]	173
Defined Benefit Plan, Interest Cost	6		7		9
Defined Benefit Plan, Contributions by Plan Participants	21		22
Defined Benefit Plan, Actuarial Gain (Loss)	1		(2)
Defined Benefit Plan, Benefits Paid	(41)		(36)
Defined Benefit Plan, Gross Prescription Drug Subsidy Receipts Received	3		3
Defined Benefit Plan, Plan Amendments	(76)		0
Benefit obligation, end of year	$ 81	[1],[2]	$ 167	[1],[2]	$ 173

[1] 1 Includes $80 million and $91 million of benefit obligations for the unfunded nonqualified supplemental pension plans at December 31, 2013 and 2012, respectively.

[2] 2 Plan remeasured at December 31, 2013 due to plan amendment.