Summary Of Net Periodic Benefit Cost (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Employee Benefit Plans [Abstract]
Service cost	$ 5	$ 5	$ 5
Interest cost	22	29	26
Expected return on plan assets	(31)	(32)	(28)
Amortization of unrecognized amounts	5	3	15
Net periodic benefit cost	$ 1	$ 5	$ 18