Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pension Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	$ 28	$ 29
Defined Benefit Plan, Expected Return on Plan Assets	(46)	(43)
Recognized net actuarial loss	6	6
Net periodic benefit cost	(12)	(8)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	1	2
Defined Benefit Plan, Expected Return on Plan Assets	(1)	(2)
Recognized net actuarial loss	0	0
Net periodic benefit cost	$ 0	$ 0