2.2.0.7 true Regulatory Matters - Additional Information (Detail) (USD $) 171 - Disclosure - Regulatory Matters - Additional Information (Detail) true false In Millions false false 1 false false pure Standard http://www.xbrl.org/2003/instance pure 0 false 2 USD false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 3 USD true false false false Virginia Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_VirginiaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false Virginia Fuel Expenses us-gaap_GainContingenciesByNatureAxis xbrldi http://xbrl.org/2006/xbrldi d_VirginiaFuelExpensesMember us-gaap_GainContingenciesByNatureAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 4 USD true false false false Virginia Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_VirginiaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false Rider R us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_RiderRMember us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 5 USD true false false false Virginia Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_VirginiaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false Rider S us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_RiderSMember us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 pure Standard http://www.xbrl.org/2003/instance pure 0 $ false 6 USD true false false false North Carolina Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false North Carolina Fuel Expenses us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaFuelExpensesMember us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 pure Standard http://www.xbrl.org/2003/instance pure 0 $ false 7 USD true false false false North Carolina Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false North Carolina Fuel Expenses us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaFuelExpensesMember us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 8 USD true false false false North Carolina Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false North Carolina Base Rate Case us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaBaseRateCaseMember us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 9 USD true false false false North Carolina Regulation us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaRegulationMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember false false North Carolina Base Rate Case us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_NorthCarolinaBaseRateCaseMember us-gaap_SignificantPurchaseAndSupplyCommitmentExcludingLongtermCommitmentByTypeAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 10 USD true false false false Ohio Pipeline Infrastructure Replacement us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_OhioPipelineInfrastructureReplacementMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 11 USD true false false false Ohio Pipeline Infrastructure Replacement us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis xbrldi http://xbrl.org/2006/xbrldi d_OhioPipelineInfrastructureReplacementMember us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis explicitMember iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ 5 Electric transmission costs from ODEC and NCEMC complaint 3 d_ElectricTransmissionCostsComplaint d false debit duration Electric transmission costs related to certain projects for which ODEC and NCEMC have filed a complaint with FERC. false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 true true false false 223000000 223 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary Electric transmission costs related to certain projects for which ODEC and NCEMC have filed a complaint with FERC. No authoritative reference available. false 6 Fuel factor application annual decrease in fuel expense recovery 3 d_ProposedAnnualIncreaseDecreaseInRecoveryFromCustomersOfFuelExpenseRecovery d false debit duration The Proposed Annual Increase Or Decrease In Recovery From Customers Of Fuel Expenses false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false true false false 82000000 82 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false true false false 28000000 28 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary The Proposed Annual Increase Or Decrease In Recovery From Customers Of Fuel Expenses No authoritative reference available. false 7 Proposed revenue requirement under Rider to go into effect April 1, 2011 for the rate year ending March 31, 2012 3 d_ProposedRiderRevenueRequirement d false credit duration The Proposed Annual Revenue Requirement false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false true false false 86000000 86 true false false 5 false true false false 200000000 200 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary The Proposed Annual Revenue Requirement No authoritative reference available. false 8 Proposed return on equity utilized in Riders R and S filings 3 d_RiderFilingReturnOnEquity d false na duration Return On Equity Utilized In Rider Filings false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false true false false 0.123 0.123 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false us-types:percentItemType pure Return On Equity Utilized In Rider Filings No authoritative reference available. false 9 Placeholder Return on Equity 3 d_RiderFilingPlaceholderReturnOnEquity d false na duration Placeholder return on equity used in rider filing. false false false false false false false false false false false false 1 false true false false 0.113 0.113 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false us-types:percentItemType pure Placeholder return on equity used in rider filing. No authoritative reference available. false 10 North Carolina base rate application increase 3 d_ProposedAnnualIncreaseDecreaseInBaseRates d false credit duration Proposed Annual Increase (Decrease) in Base Rates false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false true false false 27000000 27 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary Proposed Annual Increase (Decrease) in Base Rates No authoritative reference available. false 11 North Carolina base revenue increase from proposed settlement 3 d_ProposedIncreaseDecreaseInBaseRevenue d false credit duration Proposed Increase (Decrease) in Base Revenue false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false true false false 8000000 8 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary Proposed Increase (Decrease) in Base Revenue No authoritative reference available. false 12 North Carolina fuel revenue decrease from proposed settlement 3 d_ProposedIncreaseDecreaseInFuelRevenue d false credit duration Proposed Increase (Decrease) in Fuel Revenue false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 32000000 32 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary Proposed Increase (Decrease) in Fuel Revenue No authoritative reference available. false 13 Percentage of recovery of net energy costs of power purchases from certain wholesale providers through fuel rates 3 d_ProposedPercentageRecoveryOfCertainEnergyCostsThroughFuelRates d false na duration Proposed Percentage Recovery of Certain Energy Costs Through Fuel Rates false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false true false false 0.85 0.85 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false false false false 0 0 true false false us-types:percentItemType pure Proposed Percentage Recovery of Certain Energy Costs Through Fuel Rates No authoritative reference available. false 14 East Ohio proposed PIR Revenue Requirement 3 d_ProposedRevenueRequirement d false credit duration Proposed Revenue Requirement false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 false false false false 0 0 true false false 11 false true false false 28000000 28 true false false xbrli:monetaryItemType monetary Proposed Revenue Requirement No authoritative reference available. false 15 East Ohio proposed PIR Revenue Requirement Settlement Agreement 3 d_ProposedRevenueRequirementSettlementAgreement d false credit duration Proposed Revenue Requirement, Settlement Agreement false false false false false false false false false false false false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 true false false 4 false false false false 0 0 true false false 5 false false false false 0 0 true false false 6 false false false false 0 0 true false false 7 false false false false 0 0 true false false 8 false false false false 0 0 true false false 9 false false false false 0 0 true false false 10 true true false false 27000000 27 true false false 11 false false false false 0 0 true false false xbrli:monetaryItemType monetary Proposed Revenue Requirement, Settlement Agreement No authoritative reference available. false 11 11 false Millions UnKnown UnKnown false true