Pension and Other Postretirement Benefits - Schedule of Reconciliation of Activity for Investments (Parenthetical) (Detail) (Pension and Other Postretirement Benefit Plans' Assets [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Pension and Other Postretirement Benefit Plans' Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Transfer into level 3	$ 0
Transfer out of level 3		$ 0