Employee Benefits - Components of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost		$ 1
Interest cost	10	9
Expected return on assets	(12)	(11)
Recognized actuarial net (gain) loss	3	3
Net periodic benefit cost (credit)	1	2
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost
Interest cost	1	1
Expected return on assets
Recognized actuarial net (gain) loss	(2)	(2)
Net periodic benefit cost (credit)	$ (1)	$ (1)