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[Abstract]25false0us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeNetGainLossBeforeTaxus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse80000008falsefalsefalsefalsefalse2truefalsefalse1600000016falsefalsefalsefalsefalse3truefalsefalse2200000022falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate net gain or loss recognized in other comprehensive income, including amounts arising during the period and reclassification adjustments of other comprehensive income as a result of being recognized as components of net periodic benefit cost for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph i Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a falsefalseNet actuarial gain (loss)26false0us-gaap_OtherComprehensiveIncomeReclassificationOfDefinedBenefitPlansNetGainLossRecognizedInNetPeriodicBenefitCostBeforeTaxus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-3000000-3falsefalsefalsefalsefalse2truefalsefalse-2000000-2falsefalsefalsefalsefalse3falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net gain or loss previously recognized in other comprehensive income that is a reclassification adjustment of other comprehensive income as a result of being recognized as a component of net periodic benefit cost for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph d Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph i Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a falsefalseAmortization of net actuarial (gain) loss27false0us-gaap_OtherComprehensiveIncomeAmortizationOfDefinedBenefitPlanNetPriorServiceCostCreditRecognizedInNetPeriodicBenefitCostBeforeTaxus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1truefalsefalse-1000000-1falsefalsefalsefalsefalse2truefalsefalse-1000000-1falsefalsefalsefalsefalse3truefalsefalse-1000000-1falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net prior service cost or credit recognized in other comprehensive income that is a reclassification adjustment of other comprehensive income as a result of being recognized as a component of net periodic benefit cost for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 19, 24 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 4 -Subparagraph c, d Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph 5 -Subparagraph i Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a falsefalseAmortization of net prior service cost (credit)28false0us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentBeforeTaxPeriodIncreaseDecreaseus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse40000004falsetruefalsefalsefalse2truefalsefalse1300000013falsetruefalsefalsefalse3truefalsefalse2100000021falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmounts recognized in other comprehensive income (but not yet recognized in net periodic benefit cost), including the net gain (loss) and net prior service cost (credit) arising during the period. Also includes reclassification adjustments out of other comprehensive income as a result of being recognized as components of net periodic benefit cost for the period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 132R -Paragraph C3 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 14, 17, 22, 26 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(3) Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 158 -Paragraph 7 -Subparagraph a truefalseTotal amounts recognized in other comprehensive income (expense)328Components of Net Periodic Benefit Cost and Amounts Recognized in Other Comprehensive Income (Expense) Table (Detail) (USD $)MillionsUnKnownUnKnownUnKnownfalsetrue