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Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 16 Washington Gas Light Company 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 3 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ false 4 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 $ na No definition available. 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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 false 21 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 22 Preferred stock, par value 2 us-gaap_PreferredStockParOrStatedValuePerShare us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 0 0 false false false 2 true true false false 0 0 false false false us-types:perShareItemType decimal Face amount or stated value per share of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer); generally not indicative of the fair market value per share. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 3, 4, 5, 6, 7, 8 false 23 Preferred stock, shares authorized 2 us-gaap_PreferredStockSharesAuthorized us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1500000 1500000 false false false 2 false true false false 1500000 1500000 false false false xbrli:sharesItemType shares The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 3, 4, 5, 6, 7, 8 false 31 Washington Gas Light Company | Due fiscal year 2010, 1.19% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 5 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2010, 1.19% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 42 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 43 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0119 0.0119 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 46 Washington Gas Light Company | Due fiscal year 2010, 7.50% to 7.70% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 6 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2010, 7.50% to 7.70% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 57 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 59 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.075 0.075 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 60 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.077 0.077 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 61 Washington Gas Light Company | Due fiscal year 2011, 6.64% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 7 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2011, 6.64% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 72 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 73 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0664 0.0664 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 76 Washington Gas Light Company | Due fiscal year 2012, 5.90% to 6.05% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 8 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2012, 5.90% to 6.05% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 87 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 89 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.059 0.059 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 90 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0605 0.0605 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 91 Washington Gas Light Company | Due fiscal year 2014, 4.88% to 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 9 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2014, 4.88% to 5.17% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 102 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 104 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0488 0.0488 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 105 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0517 0.0517 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 106 Washington Gas Light Company | Due fiscal year 2015, 4.83% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 10 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2015, 4.83% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 117 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 118 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0483 0.0483 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 121 Washington Gas Light Company | Due fiscal year 2016, 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 11 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2016, 5.17% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 132 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 133 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0517 0.0517 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 136 Washington Gas Light Company | Due fiscal year 2019, 7.46% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 12 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2019, 7.46% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 147 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 148 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0746 0.0746 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 151 Washington Gas Light Company | Due fiscal year 2020, 4.76% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 13 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2020, 4.76% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 162 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 163 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0476 0.0476 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 166 Washington Gas Light Company | Due fiscal year 2023, 6.65% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 14 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2023, 6.65% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 177 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 178 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0665 0.0665 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 181 Washington Gas Light Company | Due fiscal year 2025, 5.44% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 15 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2025, 5.44% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 192 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 193 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0544 0.0544 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 196 Washington Gas Light Company | Due fiscal year 2027, 6.40% to 6.82% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 16 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2027, 6.40% to 6.82% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 207 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 209 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.064 0.064 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 210 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0682 0.0682 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 211 Washington Gas Light Company | Due fiscal year 2028, 6.57% to 6.85% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 17 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2028, 6.57% to 6.85% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 222 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 224 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0657 0.0657 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 225 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0685 0.0685 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 226 Washington Gas Light Company | Due fiscal year 2030, 7.50% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 18 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2030, 7.50% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 237 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 238 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.075 0.075 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 241 Washington Gas Light Company | Due fiscal year 2036, 5.70% to 5.78% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 19 true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false Due fiscal year 2036, 5.70% to 5.78% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 252 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 254 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.057 0.057 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 255 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0578 0.0578 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 256 Washington Gas Light Company | $4.80 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 20 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $4.80 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 21 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $4.80 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 261 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 264 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 150000 150000 false false false 2 false true false false 150000 150000 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 265 Preferred stock, shares issued 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 150000 150000 false false false 2 false true false false 150000 150000 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 266 Dividend rate on preferred stock 2 wgl_PreferredStockDividendPerDollarAmount wgl false na instant Preferred Stock Dividend Per Dollar Amount. false false false false false false false false false false false verboselabel false 1 false true false false 4.8 4.8 false false false 2 false true false false 4.8 4.8 false false false xbrli:decimalItemType decimal Preferred Stock Dividend Per Dollar Amount. No authoritative reference available. false 271 Washington Gas Light Company | $4.25 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 22 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $4.25 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 23 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $4.25 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 276 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 279 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 70600 70600 false false false 2 false true false false 70600 70600 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 280 Preferred stock, shares issued 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 70600 70600 false false false 2 false true false false 70600 70600 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 281 Dividend rate on preferred stock 2 wgl_PreferredStockDividendPerDollarAmount wgl false na instant Preferred Stock Dividend Per Dollar Amount. false false false false false false false false false false false verboselabel false 1 false true false false 4.25 4.25 false false false 2 false true false false 4.25 4.25 false false false xbrli:decimalItemType decimal Preferred Stock Dividend Per Dollar Amount. No authoritative reference available. false 286 Washington Gas Light Company | $5.00 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 24 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $5.00 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 25 USD true false false false Washington Gas Light Company dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_SubsidiariesMember dei_LegalEntityAxis explicitMember false false $5.00 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 291 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 294 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 60000 60000 false false false 2 false true false false 60000 60000 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 295 Preferred stock, shares issued 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 60000 60000 false false false 2 false true false false 60000 60000 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 296 Dividend rate on preferred stock 2 wgl_PreferredStockDividendPerDollarAmount wgl false na instant Preferred Stock Dividend Per Dollar Amount. false false false false false false false false false false false verboselabel false 1 false true false false 5 5 false false false 2 false true false false 5 5 false false false xbrli:decimalItemType decimal Preferred Stock Dividend Per Dollar Amount. No authoritative reference available. false 301 Due fiscal year 2010, 1.19% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 26 USD true false false false Due fiscal year 2010, 1.19% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearOneMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 312 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 313 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0119 0.0119 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 316 Due fiscal year 2010, 7.50% to 7.70% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 27 true false false false Due fiscal year 2010, 7.50% to 7.70% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwoMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 327 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 329 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.075 0.075 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 330 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.077 0.077 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 331 Due fiscal year 2011, 6.64% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 28 USD true false false false Due fiscal year 2011, 6.64% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThreeMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 342 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 343 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0664 0.0664 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 346 Due fiscal year 2012, 5.90% to 6.05% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 29 true false false false Due fiscal year 2012, 5.90% to 6.05% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 357 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 359 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.059 0.059 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 360 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0605 0.0605 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 361 Due fiscal year 2014, 4.88% to 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 30 true false false false Due fiscal year 2014, 4.88% to 5.17% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFiveMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 372 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 374 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0488 0.0488 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 375 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0517 0.0517 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 376 Due fiscal year 2015, 4.83% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 31 USD true false false false Due fiscal year 2015, 4.83% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSixMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 387 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 388 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0483 0.0483 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 391 Due fiscal year 2016, 5.17% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 32 USD true false false false Due fiscal year 2016, 5.17% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearSevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 402 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 403 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0517 0.0517 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 406 Due fiscal year 2019, 7.46% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 33 USD true false false false Due fiscal year 2019, 7.46% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearEightMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 417 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 418 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0746 0.0746 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 421 Due fiscal year 2020, 4.76% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 34 USD true false false false Due fiscal year 2020, 4.76% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearNineMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 432 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 433 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0476 0.0476 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 436 Due fiscal year 2023, 6.65% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 35 USD true false false false Due fiscal year 2023, 6.65% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 447 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 448 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0665 0.0665 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 451 Due fiscal year 2025, 5.44% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 36 USD true false false false Due fiscal year 2025, 5.44% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearElevenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 462 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 463 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0544 0.0544 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 466 Due fiscal year 2027, 6.40% to 6.82% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 37 true false false false Due fiscal year 2027, 6.40% to 6.82% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearTwelveMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 477 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 479 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.064 0.064 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 480 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0682 0.0682 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 481 Due fiscal year 2028, 6.57% to 6.85% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 38 true false false false Due fiscal year 2028, 6.57% to 6.85% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearThirteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 492 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 494 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0657 0.0657 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 495 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0685 0.0685 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 496 Due fiscal year 2030, 7.50% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 39 USD true false false false Due fiscal year 2030, 7.50% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFourteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ na No definition available. No authoritative reference available. false 507 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 508 Interest Rate on Debt Instrument 2 us-gaap_DebtInstrumentInterestRateStatedPercentage us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.075 0.075 false false false 2 false false false false 0 0 false false false us-types:percentItemType pure Interest rate stated in the contractual debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 511 Due fiscal year 2036, 5.70% to 5.78% 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 40 true false false false Due fiscal year 2036, 5.70% to 5.78% us-gaap_LongtermDebtTypeAxis xbrldi http://xbrl.org/2006/xbrldi wgl_UnsecuredMediumTermNotesDueInYearFifteenMember us-gaap_LongtermDebtTypeAxis explicitMember Pure Standard http://www.xbrl.org/2003/instance pure xbrli 0 na No definition available. No authoritative reference available. false 522 Long-Term Debt 2 us-gaap_LongTermDebtByComponentsAlternativeAbstract us-gaap true na duration No definition available. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 524 Interest Rate on Debt Instrument, Minimum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMinimum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.057 0.057 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the lowest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 525 Interest Rate on Debt Instrument, Maximum 2 us-gaap_DebtInstrumentInterestRateStatedPercentageRateRangeMaximum us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 0.0578 0.0578 false false false 2 false false false false 0 0 false false false xbrli:pureItemType pure When presenting a range of interest rates, the highest stated (contractual) rate for funds borrowed under the debt agreement as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 false 526 $4.80 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 41 USD true false false false $4.80 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 42 USD true false false false $4.80 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesOneMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 531 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 534 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 150000 150000 false false false 2 false true false false 150000 150000 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. 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No authoritative reference available. false 541 $4.25 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 43 USD true false false false $4.25 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 44 USD true false false false $4.25 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesTwoMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 546 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 549 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 70600 70600 false false false 2 false true false false 70600 70600 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 550 Preferred stock, shares issued 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 70600 70600 false false false 2 false true false false 70600 70600 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. 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No authoritative reference available. false 556 $5.00 series 0 na true na na No definition available. false true false false false false false false false false false http://wglholdings.com/role/statementofcapitalizationparenthetical false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false false 45 USD true false false false $5.00 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 46 USD true false false false $5.00 series us-gaap_StatementClassOfStockAxis xbrldi http://xbrl.org/2006/xbrldi wgl_SeriesThreeMember us-gaap_StatementClassOfStockAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 561 Preferred Stock 2 wgl_PreferredStockAbstract wgl false na duration Preferred stock. false false false false false true false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false xbrli:stringItemType string Preferred stock. false 564 Preferred stock, shares outstanding 2 us-gaap_PreferredStockSharesOutstanding us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 60000 60000 false false false 2 false true false false 60000 60000 false false false xbrli:sharesItemType shares Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 565 Preferred stock, shares issued 2 us-gaap_PreferredStockSharesIssued us-gaap true na instant No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 60000 60000 false false false 2 false true false false 60000 60000 false false false xbrli:sharesItemType shares Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29 -Article 5 false 566 Dividend rate on preferred stock 2 wgl_PreferredStockDividendPerDollarAmount wgl false na instant Preferred Stock Dividend Per Dollar Amount. false false false false false false false false false false false verboselabel false 1 false true false false 5 5 false false false 2 false true false false 5 5 false false false xbrli:decimalItemType decimal Preferred Stock Dividend Per Dollar Amount. No authoritative reference available. false 2 148 false UnKnown NoRounding NoRounding true true