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Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 true 31 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/statementsofincome false 1 false false false false 0 0 false false false 2 false false false false 0 0 false false false 3 false false false false 0 0 false false false 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 $ 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 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 6 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 $ na No definition available. No authoritative reference available. false 32 OPERATING REVENUES 2 us-gaap_OilAndGasRevenueAbstract 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 3 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 33 Utility 2 us-gaap_RegulatedOperatingRevenueGas us-gaap true credit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 1321446000 1321446 false false false 2 false true false false 1505875000 1505875 false false false 3 false true false false 1552344000 1552344 false false false xbrli:monetaryItemType monetary The amount of regulated gas operating revenues recognized during the period. 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No authoritative reference available. false 41 General taxes and other assessments 2 wgl_GeneralTaxesAndOtherAssessments wgl false debit duration General taxes and other assessments. false false false false false false false false false false false totallabel false 1 false true false false 115454000 115454 false false false 2 false true false false 109522000 109522 false false false 3 false true false false 98721000 98721 false false false xbrli:monetaryItemType monetary General taxes and other assessments. 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No authoritative reference available. true 48 Total Interest Expense 2 us-gaap_InterestExpense us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 39924000 39924 false false false 2 false true false false 44133000 44133 false false false 3 false true false false 45356000 45356 false false false xbrli:monetaryItemType monetary The cost of borrowed funds accounted for as interest that was charged against earnings during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher OTS -Name Federal Regulation (FR) -Number Title 12 -Chapter V -Section 563c.102 -Paragraph 9 -Subsection II Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 9 -Article 9 true 49 INCOME BEFORE INCOME TAXES 2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments us-gaap true credit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 169430000 169430 false false false 2 false true false false 172603000 172603 false false false 3 false true false false 178889000 178889 false false false xbrli:monetaryItemType monetary Sum of operating profit and nonoperating income (expense) before income (loss) from equity method investments, income taxes, extraordinary items, cumulative effects of changes in accounting principles, and noncontrolling interest. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Subparagraph 1(i) -Article 4 false 50 INCOME TAX EXPENSE 2 us-gaap_IncomeTaxExpenseBenefit us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 67081000 67081 false false false 2 false true false false 66018000 66018 false false false 3 false true false false 64707000 64707 false false false xbrli:monetaryItemType monetary The sum of the current income tax expense (benefit) and the deferred income tax expense (benefit) pertaining to continuing operations. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph h -Article 4 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 109 -Paragraph 45 -Subparagraph a, b true 51 NET INCOME 2 us-gaap_NetIncomeLoss us-gaap true credit duration No definition available. false false false false false false false false false false false terselabel false 1 false true false false 102349000 102349 false false false 2 false true false false 106585000 106585 false false false 3 false true false false 114182000 114182 false false false xbrli:monetaryItemType monetary The portion of consolidated profit or loss for the period, net of income taxes, which is attributable to the parent. If the entity does not present consolidated financial statements, the amount of profit or loss for the period, net of income taxes. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 19 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph d Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A7 -Appendix A Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph a Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 20 -Article 9 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 10, 15 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Emerging Issues Task Force (EITF) -Number 87-21 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28, 29, 30 false 52 Dividends on Washington Gas preferred stock 2 us-gaap_PreferredStockDividends us-gaap true debit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 1320000 1320 false false false 2 false true false false 1320000 1320 false false false 3 false true false false 1320000 1320 false false false xbrli:monetaryItemType monetary The amount of dividends declared or paid in the period to preferred shareholders, or the amount for which the obligation to pay them dividends arose in the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 6 -Section B Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -Subparagraph b true 53 NET INCOME APPLICABLE TO COMMON STOCK 2 us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 true true false false 101029000 101029 false false false 2 true true false false 105265000 105265 false false false 3 true true false false 112862000 112862 false false false xbrli:monetaryItemType monetary Net income after adjustments for dividends on preferred stock (declared in the period) and/or cumulative preferred stock (accumulated for the period). 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