2.2.0.7 true Credit Risk - Additional Information (Detail) (USD $) 179 - Disclosure - Credit Risk - Additional Information (Detail) true false In Millions false false 1 USD false false iso4217_USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 iso4217_USD_per_shares Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares 0 shares Standard http://www.xbrl.org/2003/instance shares 0 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 shares Standard http://www.xbrl.org/2003/instance shares 0 $ 2 Gross credit exposure 2 us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure us-gaap true debit duration No definition available. false false false false false false false false false false false false 1 true true false false 756000000 756 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Reflects the maximum amount of loss due to credit risk that, based on the gross fair value of the financial instrument, the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts and the collateral or other security, if any, for the amount due proved to be of no value to the entity Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 107 -Paragraph 15A -Subparagraph b false 3 Our credit exposure after the application of collateral 2 d_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposureNet d false credit duration Reflects the maximum amount of loss due to credit risk, after application of collateral, that the entity would incur if... false false false false false false false false false false false false 1 false true false false 676000000 676 false false false 2 false false false false 0 0 false false false xbrli:monetaryItemType monetary Reflects the maximum amount of loss due to credit risk, after application of collateral, that the entity would incur if parties to the financial instruments that make up the concentration failed completely to perform according to the terms of the contracts. No authoritative reference available. false 5 Additional Collateral to be posted if the credit-risk-related contingent features were triggered 2 us-gaap_AdditionalCollateralAggregateFairValue us-gaap true debit instant No definition available. false false false false false false false false false false false false 1 false true false false 90000000 90 false false false 2 false true false false 36000000 36 false false false xbrli:monetaryItemType monetary The aggregate fair value of additional assets that would be required to be posted as collateral for derivative instruments with credit-risk-related contingent features if the credit-risk-related contingent features were triggered at the end of the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph c false 6 Collateral already posted 2 us-gaap_CollateralAlreadyPostedAggregateFairValue us-gaap true debit instant No definition available. false false false false false false false false false false false false 1 false true false false 52000000 52 false false false 2 false true false false 62000000 62 false false false xbrli:monetaryItemType monetary The aggregate fair value of assets that are already posted, at the end of the reporting period, as collateral for derivative instruments with credit-risk-related contingent features. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 44D -Subparagraph c false 7 Letters of credit included in the collateral posted 2 us-gaap_SecuritiesReceivedAsCollateral us-gaap true debit instant No definition available. false false false false false false false false false false false false 1 false true false false 19000000 19 false false false 2 false true false false 48000000 48 false false false xbrli:monetaryItemType monetary The carrying value as of the balance sheet date of the assets received as collateral against securities loaned to other broker-dealers. Borrowers of securities generally are required to provide collateral to the lenders of securities, commonly cash but sometimes other securities or standby letters of credit, with a value slightly higher than that of the securities borrowed. In instances where the entity is permitted to sell or re-pledge these securities, the entity reports the fair value of the collateral received and the related obligation to return the collateral as a liability Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Audit and Accounting Guide (AAG) -Number AAG-BRD -Chapter 4 -Paragraph 49 -IssueDate 2006-05-01 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 140 -Paragraph 17 -Subparagraph a(3) Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 140 -Paragraph 15 -Subparagraph a, b, c, d Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 140 -Paragraph 91 false 8 Fair value of all dervative instruments not fully collateralized 2 us-gaap_DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral us-gaap true credit instant No definition available. false false false false false false false false false false false false 1 true true false false 196000000 196 false false false 2 true true false false 181000000 181 false false false xbrli:monetaryItemType monetary The amount as of the balance sheet date of the fair value of derivative liabilities that in accordance with the entity's accounting policy was not offset against the right to reclaim cash collateral under a master netting arrangement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FIN39-1 -Paragraph 10B -Subparagraph a false 9 Investment grade | Internal Credit Rating 0 na true na na No definition available. false true false false false false false false false false false http://www.dom.com/taxonomy/role/disclosurecreditriskadditionalinformation false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 3 true false false false Investment grade us-gaap_ConcentrationRiskByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_InvestmentGradeMember us-gaap_ConcentrationRiskByTypeAxis explicitMember false false Internal Credit Rating us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_InternalCreditRatingMember us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis explicitMember pure Standard http://www.xbrl.org/2003/instance pure 0 na No definition available. No authoritative reference available. false 12 Concentration of credit risk 2 us-gaap_ConcentrationRiskPercentage us-gaap true na instant No definition available. false false false false false false false false false false false false 1 false true false false 0.86 0.86 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. No authoritative reference available. false 17 Investment grade | Counterparty, A 0 na true na na No definition available. false true false false false false false false false false false http://www.dom.com/taxonomy/role/disclosurecreditriskadditionalinformation false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 4 true false false false Investment grade us-gaap_ConcentrationRiskByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_InvestmentGradeMember us-gaap_ConcentrationRiskByTypeAxis explicitMember false false Counterparty, A us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis xbrldi http://xbrl.org/2006/xbrldi d_CounterpartyAMember us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis explicitMember pure Standard http://www.xbrl.org/2003/instance pure 0 na No definition available. No authoritative reference available. false 20 Concentration of credit risk 2 us-gaap_ConcentrationRiskPercentage us-gaap true na instant No definition available. false false false false false false false false false false false false 1 false true false false 0.1 0.1 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. No authoritative reference available. false 25 Investment grade | Counterparty, B 0 na true na na No definition available. false true false false false false false false false false false http://www.dom.com/taxonomy/role/disclosurecreditriskadditionalinformation false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 5 true false false false Investment grade us-gaap_ConcentrationRiskByTypeAxis xbrldi http://xbrl.org/2006/xbrldi d_InvestmentGradeMember us-gaap_ConcentrationRiskByTypeAxis explicitMember false false Counterparty, B us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis xbrldi http://xbrl.org/2006/xbrldi d_CounterpartyBMember us-gaap_GuaranteeObligationsByPaymentAndPerformanceRiskCreditRatingAxis explicitMember pure Standard http://www.xbrl.org/2003/instance pure 0 na No definition available. No authoritative reference available. false 28 Concentration of credit risk 2 us-gaap_ConcentrationRiskPercentage us-gaap true na instant No definition available. false false false false false false false false false false false false 1 false true false false 0.13 0.13 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. No authoritative reference available. false 2 12 false Millions UnKnown UnKnown false true