Summary Of Net Periodic Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefit Plans [Abstract]
Service cost	$ 5	$ 3	$ 2
Interest cost	27	17	12
Expected return on plan assets	(25)	(17)	(11)
Amortization of unrecognized amounts	14	8	6
Net periodic benefit cost	$ 21	$ 11	$ 9