Employee Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 1		$ 1	$ 1
Interest cost	9	9	19	18
Expected return on assets	(12)	(11)	(24)	(22)
Recognized actuarial net (gain) loss	2	4	5	7
Net periodic benefit cost (credit)		2	1	4
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	1	1	2	2
Prior service credit		(1)		(1)
Recognized actuarial net (gain) loss	(2)	(1)	(4)	(3)
Net periodic benefit cost (credit)	$ (1)	$ (1)	$ (2)	$ (2)