Pension and Other Postretirement Benefits - Components of Pension Expense for Defined Benefit Pension Plan (Detail) (Pension Plan, Defined Benefit [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Pension Plan, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period	$ 5	$ 4	$ 5
Interest cost on projected benefit obligation	50	47	33
Expected return on assets	(61)	(65)	(39)
Recognized losses	35	33	18
Curtailment gain		(4)	(1)
Amortization of prior service costs		(1)
Net periodic postretirement benefit cost	$ 29	$ 14	$ 16