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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
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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

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- Definition Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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