Pension and Other Postretirement Benefits - Schedule of Reconciliation of Activity for Investments (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]
Balance at beginning of year	$ 3,119	$ 2,816
Realized gains	140	56
Unrealized gains	173	140
Purchases	636	636
Sales	(626)	(538)
Issuances
Settlements
Foreign currency translation impact	(21)	9
Transfers in and/or out of Level 3
Balance at end of year	$ 3,421	$ 3,119