Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	$ 31	$ 28
Defined Benefit Plan, Expected Return on Plan Assets	(49)	(46)
Defined Benefit Plan, Amortization of Gains (Losses)	4	6
Net periodic benefit cost	(14)	(12)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Interest Cost	1	1
Defined Benefit Plan, Expected Return on Plan Assets	(2)	(1)
Defined Benefit Plan, Amortization of Gains (Losses)	(1)	0
Net periodic benefit cost	$ (2)	$ 0