Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Pension Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	$ 28	$ 31	$ 56	$ 60
Defined Benefit Plan, Expected Return on Plan Assets	(47)	(43)	(93)	(86)
Defined Benefit Plan, Actuarial Gain (Loss)	(7)	(6)	(13)	(12)
Net periodic benefit cost	(12)	(6)	(24)	(14)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	2	1	3	3
Defined Benefit Plan, Expected Return on Plan Assets	(2)	(1)	(3)	(3)
Defined Benefit Plan, Actuarial Gain (Loss)	0	0	0	0
Net periodic benefit cost	$ 0	$ 0	$ 0	$ 0