2.2.0.7 true Consolidated Statements of Income (Unaudited) (USD $) 0120 - Statement - Consolidated Statements of Income (Unaudited) true false In Thousands, except Per Share data false false 1 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 3 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 4 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ 1 WGL Holdings, Inc. 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 4 false false false false 0 0 false false false false 1 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 2 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 3 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ false 4 USD true false false false WGL Holdings, Inc. dei_LegalEntityAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_ParentCompanyMember dei_LegalEntityAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDEPS Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 $ na No definition available. No authoritative reference available. false 2 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 3 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 true true false false 168379000 168379 false false false 2 true true false false 185958000 185958 false false false 3 true true false false 1170536000 1170536 false false false 4 true true false false 1350836000 1350836 false false false xbrli:monetaryItemType monetary The amount of regulated gas operating revenues recognized during the period. No authoritative reference available. false 4 Non-utility 2 us-gaap_UnregulatedOperatingRevenue 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 291294000 291294 false false false 2 false true false false 241078000 241078 false false false 3 false true false false 1073198000 1073198 false false false 4 false true false false 943176000 943176 false false false xbrli:monetaryItemType monetary The amount of unregulated operating revenues recognized during the period. No authoritative reference available. false 5 Total Operating Revenues 2 us-gaap_RegulatedAndUnregulatedOperatingRevenue us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 459673000 459673 false false false 2 false true false false 427036000 427036 false false false 3 false true false false 2243734000 2243734 false false false 4 false true false false 2294012000 2294012 false false false xbrli:monetaryItemType monetary The total amount of operating revenues recognized during the period. No authoritative reference available. true 6 OPERATING EXPENSES 2 us-gaap_OperatingExpensesAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 7 Utility cost of gas 2 wgl_UtilityCostOfGas wgl false debit duration Utility cost of gas. false false false false false false false false false false false verboselabel false 1 false true false false 60001000 60001 false false false 2 false true false false 75185000 75185 false false false 3 false true false false 576200000 576200 false false false 4 false true false false 757112000 757112 false false false xbrli:monetaryItemType monetary Utility cost of gas. No authoritative reference available. false 8 Non-utility cost of energy-related sales 2 wgl_NonutilityCostOfEnergyRelatedSales wgl false debit duration Non-utility cost of energy-related sales. false false false false false false false false false false false verboselabel false 1 false true false false 243983000 243983 false false false 2 false true false false 222160000 222160 false false false 3 false true false false 1008971000 1008971 false false false 4 false true false false 901472000 901472 false false false xbrli:monetaryItemType monetary Non-utility cost of energy-related sales. No authoritative reference available. false 9 Operation and maintenance 2 wgl_OperationAndMaintenanceExpenses wgl false debit duration Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly... false false false false false false false false false false false verboselabel false 1 false true false false 79062000 79062 false false false 2 false true false false 71448000 71448 false false false 3 false true false false 230850000 230850 false false false 4 false true false false 220221000 220221 false false false xbrli:monetaryItemType monetary Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes Selling, General and Administrative Expense. No authoritative reference available. false 10 Depreciation and amortization 2 us-gaap_UtilitiesOperatingExpenseDepreciationAndAmortization us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 23634000 23634 false false false 2 false true false false 23168000 23168 false false false 3 false true false false 72032000 72032 false false false 4 false true false false 71494000 71494 false false false xbrli:monetaryItemType monetary Discloses the amount of operating expense for the period related to depreciation and amortization. No authoritative reference available. false 11 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 25752000 25752 false false false 2 false true false false 22852000 22852 false false false 3 false true false false 100179000 100179 false false false 4 false true false false 94534000 94534 false false false xbrli:monetaryItemType monetary General taxes and other assessments. No authoritative reference available. true 12 Total Operating Expenses 2 us-gaap_OperatingExpenses 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 432432000 432432 false false false 2 false true false false 414813000 414813 false false false 3 false true false false 1988232000 1988232 false false false 4 false true false false 2044833000 2044833 false false false xbrli:monetaryItemType monetary Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense. No authoritative reference available. true 13 OPERATING INCOME (LOSS) 2 us-gaap_OperatingIncomeLoss 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 27241000 27241 false false false 2 false true false false 12223000 12223 false false false 3 false true false false 255502000 255502 false false false 4 false true false false 249179000 249179 false false false xbrli:monetaryItemType monetary The net result for the period of deducting operating expenses from operating revenues. No authoritative reference available. false 14 Other Income - Net 2 us-gaap_OtherNonoperatingIncomeExpense 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 280000 280 false false false 2 false true false false 818000 818 false false false 3 false true false false 1144000 1144 false false false 4 false true false false 1595000 1595 false false false xbrli:monetaryItemType monetary The net amount of other nonoperating income and expense, which does not qualify for separate disclosure on the income statement under materiality guidelines. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 false 15 Interest Expense 2 us-gaap_InterestExpenseAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 16 Interest on long-term debt 2 us-gaap_InterestExpenseDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 9913000 9913 false false false 2 false true false false 10422000 10422 false false false 3 false true false false 29816000 29816 false false false 4 false true false false 30894000 30894 false false false xbrli:monetaryItemType monetary Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 false 17 AFUDC and other, net 2 wgl_AllowanceForFundsUsedDuringConstructionAndOtherNet wgl false debit duration Allowance for Funds Used During Construction and other net. false false false false false false false false false false false totallabel false 1 false true false false 87000 87 false false false 2 false true false false 390000 390 false false false 3 false true false false 143000 143 false false false 4 false true false false 3572000 3572 false false false xbrli:monetaryItemType monetary Allowance for Funds Used During Construction and other net. No authoritative reference available. true 18 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 10000000 10000 false false false 2 false true false false 10812000 10812 false false false 3 false true false false 29959000 29959 false false false 4 false true false false 34466000 34466 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 19 INCOME (LOSS) 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 17521000 17521 false false false 2 false true false false 2229000 2229 false false false 3 false true false false 226687000 226687 false false false 4 false true false false 216308000 216308 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 20 INCOME TAX EXPENSE (BENEFIT) 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 7510000 7510 false false false 2 false true false false 92000 92 false false false 3 false true false false 89669000 89669 false false false 4 false true false false 83816000 83816 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 21 NET INCOME (LOSS) BEFORE PREFERRED STOCK DIVIDENDS 2 us-gaap_NetIncomeLoss 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 10011000 10011 false false false 2 false true false false 2137000 2137 false false false 3 false true false false 137018000 137018 false false false 4 false true false false 132492000 132492 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 22 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 330000 330 false false false 2 false true false false 330000 330 false false false 3 false true false false 990000 990 false false false 4 false true false false 990000 990 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 23 NET INCOME (LOSS) 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 false true false false 9681000 9681 false false false 2 false true false false 1807000 1807 false false false 3 false true false false 136028000 136028 false false false 4 false true false false 131502000 131502 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). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 9 true 24 AVERAGE COMMON SHARES OUTSTANDING 2 us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 25 Basic 2 us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 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 50664000 50664 false false false 2 false true false false 50141000 50141 false false false 3 false true false false 50422000 50422 false false false 4 false true false false 50092000 50092 false false false xbrli:sharesItemType shares Number of [basic] shares, after adjustment for contingently issuable shares and other shares not deemed outstanding, determined by relating the portion of time within a reporting period that common shares have been outstanding to the total time in that period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 171 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -Subparagraph a Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 8 false 26 Diluted 2 us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding us-gaap true na duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 50918000 50918 false false false 2 false true false false 50435000 50435 false false false 3 false true false false 50638000 50638 false false false 4 false true false false 50349000 50349 false false false xbrli:sharesItemType shares The average number of shares issued and outstanding that are used in calculating diluted EPS, determined based on the timing of issuance of shares in the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -Subparagraph a Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 8 true 27 EARNINGS PER AVERAGE COMMON SHARE 2 us-gaap_EarningsPerShareAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 28 Basic 2 us-gaap_EarningsPerShareBasic us-gaap true na duration No definition available. false false false false false false false false false false false verboselabel true 1 true true false false 0.19 0.19 false false false 2 true true false false 0.04 0.04 false false false 3 true true false false 2.70 2.70 false false false 4 true true false false 2.63 2.63 false false false us-types:perShareItemType decimal The amount of net income or loss for the period per each share of common stock outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 21 -Article 9 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 36, 37, 38 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 20 -Article 5 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 18 -Article 7 false 29 Diluted 2 us-gaap_EarningsPerShareDiluted us-gaap true na duration No definition available. false false false false false false false false false false false totallabel true 1 true true false false 0.19 0.19 false false false 2 true true false false 0.04 0.04 false false false 3 true true false false 2.69 2.69 false false false 4 true true false false 2.61 2.61 false false false us-types:perShareItemType decimal The amount of net income or loss for the period per each share of common stock and dilutive common stock equivalents outstanding during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 11, 12, 36 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 20 -Article 5 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 18 -Article 7 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 21 -Article 9 true 30 DIVIDENDS DECLARED PER COMMON SHARE 2 us-gaap_CommonStockDividendsPerShareDeclared us-gaap true na duration No definition available. false false false false false false false false false false false totallabel true 1 true true false false 0.3775 0.3775 false false false 2 true true false false 0.3675 0.3675 false false false 3 true true false false 1.1225 1.1225 false false false 4 true true false false 1.0900 1.0900 false false false us-types:perShareItemType decimal Aggregate dividends declared during the period for each share of common stock outstanding. 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 4 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 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 $ 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 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 $ false 8 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 4 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 172544000 172544 false false false 2 false true false false 190101000 190101 false false false 3 false true false false 1190703000 1190703 false false false 4 false true false false 1371868000 1371868 false false false xbrli:monetaryItemType monetary The amount of regulated gas operating revenues recognized during the period. No authoritative reference available. false 34 Non-utility 2 us-gaap_UnregulatedOperatingRevenue us-gaap true credit duration No definition available. false false false false false false false false false false false verboselabel false 1 false false false false 0 0 false false false 2 false true false false 11000 11 false false false 3 false true false false 2000 2 false false false 4 false true false false 33000 33 false false false xbrli:monetaryItemType monetary The amount of unregulated operating revenues recognized during the period. No authoritative reference available. false 35 Total Operating Revenues 2 us-gaap_RegulatedAndUnregulatedOperatingRevenue us-gaap true credit duration No definition available. false false false false false false false false false false false totallabel false 1 false true false false 172544000 172544 false false false 2 false true false false 190112000 190112 false false false 3 false true false false 1190705000 1190705 false false false 4 false true false false 1371901000 1371901 false false false xbrli:monetaryItemType monetary The total amount of operating revenues recognized during the period. No authoritative reference available. true 36 OPERATING EXPENSES 2 us-gaap_OperatingExpensesAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 37 Utility cost of gas 2 wgl_UtilityCostOfGas wgl false debit duration Utility cost of gas. false false false false false false false false false false false verboselabel false 1 false true false false 64166000 64166 false false false 2 false true false false 79327000 79327 false false false 3 false true false false 596367000 596367 false false false 4 false true false false 778144000 778144 false false false xbrli:monetaryItemType monetary Utility cost of gas. No authoritative reference available. false 39 Operation and maintenance 2 wgl_OperationAndMaintenanceExpenses wgl false debit duration Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly... false false false false false false false false false false false verboselabel false 1 false true false false 67874000 67874 false false false 2 false true false false 61471000 61471 false false false 3 false true false false 198869000 198869 false false false 4 false true false false 192342000 192342 false false false xbrli:monetaryItemType monetary Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes Selling, General and Administrative Expense. No authoritative reference available. false 40 Depreciation and amortization 2 us-gaap_UtilitiesOperatingExpenseDepreciationAndAmortization us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 23130000 23130 false false false 2 false true false false 22738000 22738 false false false 3 false true false false 70610000 70610 false false false 4 false true false false 70130000 70130 false false false xbrli:monetaryItemType monetary Discloses the amount of operating expense for the period related to depreciation and amortization. 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 24126000 24126 false false false 2 false true false false 21737000 21737 false false false 3 false true false false 95190000 95190 false false false 4 false true false false 91362000 91362 false false false xbrli:monetaryItemType monetary General taxes and other assessments. No authoritative reference available. true 42 Total Operating Expenses 2 us-gaap_OperatingExpenses 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 179296000 179296 false false false 2 false true false false 185273000 185273 false false false 3 false true false false 961036000 961036 false false false 4 false true false false 1131978000 1131978 false false false xbrli:monetaryItemType monetary Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense. No authoritative reference available. true 43 OPERATING INCOME (LOSS) 2 us-gaap_OperatingIncomeLoss 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 -6752000 -6752 false false false 2 false true false false 4839000 4839 false false false 3 false true false false 229669000 229669 false false false 4 false true false false 239923000 239923 false false false xbrli:monetaryItemType monetary The net result for the period of deducting operating expenses from operating revenues. No authoritative reference available. false 44 Other Income - Net 2 us-gaap_OtherNonoperatingIncomeExpense 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 188000 188 false false false 2 false true false false 774000 774 false false false 3 false true false false 948000 948 false false false 4 false true false false 1157000 1157 false false false xbrli:monetaryItemType monetary The net amount of other nonoperating income and expense, which does not qualify for separate disclosure on the income statement under materiality guidelines. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 9 -Article 5 false 45 Interest Expense 2 us-gaap_InterestExpenseAbstract 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 4 false false false false 0 0 false false false xbrli:stringItemType string No definition available. false 46 Interest on long-term debt 2 us-gaap_InterestExpenseDebt us-gaap true debit duration No definition available. false false false false false false false false false false false verboselabel false 1 false true false false 9913000 9913 false false false 2 false true false false 10422000 10422 false false false 3 false true false false 29816000 29816 false false false 4 false true false false 30887000 30887 false false false xbrli:monetaryItemType monetary Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings. Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 false 47 AFUDC and other, net 2 wgl_AllowanceForFundsUsedDuringConstructionAndOtherNet wgl false debit duration Allowance for Funds Used During Construction and other net. false false false false false false false false false false false totallabel false 1 false true false false 71000 71 false false false 2 false true false false 311000 311 false false false 3 false true false false 5000 5 false false false 4 false true false false 2864000 2864 false false false xbrli:monetaryItemType monetary Allowance for Funds Used During Construction and other net. 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 9984000 9984 false false false 2 false true false false 10733000 10733 false false false 3 false true false false 29821000 29821 false false false 4 false true false false 33751000 33751 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 (LOSS) 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 -16548000 -16548 false false false 2 false true false false -5120000 -5120 false false false 3 false true false false 200796000 200796 false false false 4 false true false false 207329000 207329 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 (BENEFIT) 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 -6191000 -6191 false false false 2 false true false false -2895000 -2895 false false false 3 false true false false 79197000 79197 false false false 4 false true false false 80115000 80115 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 (LOSS) BEFORE PREFERRED STOCK DIVIDENDS 2 us-gaap_NetIncomeLoss 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 -10357000 -10357 false false false 2 false true false false -2225000 -2225 false false false 3 false true false false 121599000 121599 false false false 4 false true false false 127214000 127214 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 330000 330 false false false 2 false true false false 330000 330 false false false 3 false true false false 990000 990 false false false 4 false true false false 990000 990 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 (LOSS) 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 -10687000 -10687 false false false 2 true true false false -2555000 -2555 false false false 3 true true false false 120609000 120609 false false false 4 true true false false 126224000 126224 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). Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 9 true 4 52 false Thousands Thousands NoRounding false true