Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Pension Plans, Defined Benefit
Defined Benefit Plan, Service Cost	$ 2	[1]	$ 2	[1]	$ 4	[1]	$ 4	[1]
Defined Benefit Plan, Actuarial Gain (Loss)	4		6		12		19
Defined Benefit Plan, Interest Cost	31		28		93		84
Defined Benefit Plan, Expected Return on Plan Assets	(50)	[1]	(48)	[1]	(150)	[1]	(143)	[1]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)					0		0
Net periodic benefit cost	(13)		(12)		(41)		(36)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan, Service Cost	0		0		0		0
Defined Benefit Plan, Actuarial Gain (Loss)	0		0		0		0
Defined Benefit Plan, Interest Cost	(1)		1		2		4
Defined Benefit Plan, Expected Return on Plan Assets	(1)		(1)		(4)		(4)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)					(4)		0
Net periodic benefit cost	$ (2)		$ 0		$ (6)		$ 0

[1] 1 Administrative fees are recognized in service cost for each of the periods presented.