Net Periodic Pension and Other Postretirement Benefit Cost (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 26	$ 24	$ 18
Interest cost	51	55	56
Expected return on plan assets	(82)	(76)	(73)
Amortization of unrecognized net loss (gain)	21	22	8
Amortization of unrecognized prior service cost	4	4	4
Net periodic benefit cost	20	29	13
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	5	4
Interest cost	9	10	10
Amortization of unrecognized net loss (gain)	1
Amortization of unrecognized prior service cost		(1)	(1)
Net periodic benefit cost	$ 16	$ 14	$ 13