2.2.0.25truefalse0010 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF RESULTS OF OPERATIONStruefalseIn Millions, except Per Share datafalse1falsefalseUSDfalsefalse1/1/2011 - 3/31/2011 USD ($) USD ($) / shares $D2011Q1http://www.sec.gov/CIK0000787250duration2011-01-01T00:00:002011-03-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDPerShareDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2falsefalseUSDfalsefalse1/1/2010 - 3/31/2010 USD ($) USD ($) / shares $D2010Q1http://www.sec.gov/CIK0000787250duration2010-01-01T00:00:002010-03-31T00:00:00USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDPerShareDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0SharesStandardhttp://www.xbrl.org/2003/instancesharesxbrli0USDUSD$2false0us-gaap_ElectricUtilityRevenueus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse494700000494.7falsetruefalsefalsefalse2truefalsefalse451200000451.2falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate revenue, whether regulated or unregulated, derived from the generation, transmission and distribution of electricity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 falsefalseRevenues3true0us-gaap_CostOfRevenueAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseCost of revenues:4false0us-gaap_FuelCostsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9980000099.8falsefalsefalsefalsefalse2truefalsefalse101900000101.9falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFuel costs incurred that are directly related to goods produced and sold and services rendered during the reporting period.No authoritative reference available.falsefalseFuel5false0us-gaap_CostOfPurchasedPowerus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse120800000120.8falsefalsefalsefalsefalse2truefalsefalse7280000072.8falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryCost of electricity purchased and sold during the reporting period.No authoritative reference available.falsefalsePurchased power6false0us-gaap_CostOfGoodsSoldElectricus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse220600000220.6falsefalsefalsefalsefalse2truefalsefalse174700000174.7falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTotal costs related to electricity produced and sold during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 5 truefalseTotal cost of revenues7false0us-gaap_GrossProfitus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse274100000274.1falsefalsefalsefalsefalse2truefalsefalse276500000276.5falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.No authoritative reference available.truefalseGross margin8true0us-gaap_OperatingExpensesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseOperating expenses:9false0us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9860000098.6falsefalsefalsefalsefalse2truefalsefalse8060000080.6falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryDiscloses the amount of operating expense for the period for routine plant maintenance, repairs and operations.No authoritative reference available.falsefalseOperation and maintenance10false0us-gaap_DepreciationDepletionAndAmortizationus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse3510000035.1falsefalsefalsefalsefalse2truefalsefalse3740000037.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.No authoritative reference available.falsefalseDepreciation and amortization11false0us-gaap_TaxesExcludingIncomeAndExciseTaxesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse3880000038.8falsefalsefalsefalsefalse2truefalsefalse3250000032.5falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAll taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.No authoritative reference available.falsefalseGeneral taxes12false0us-gaap_OperatingExpensesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse172500000172.5falsefalsefalsefalsefalse2truefalsefalse150500000150.5falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryGenerally 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.truefalseTotal operating expenses13false0us-gaap_OperatingIncomeLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse101600000101.6falsefalsefalsefalsefalse2truefalsefalse126000000126.0falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No authoritative reference available.truefalseOperating income14true0us-gaap_NonoperatingIncomeExpenseAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseOther income / (expense), net:15false0us-gaap_InvestmentIncomeNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse1000000.1falsefalsefalsefalsefalse2truefalsefalse1000000.1falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents investment income derived from investments in debt and equity securities consisting of interest income earned from investments in debt securities and on cash and cash equivalents, dividend income from investments in equity securities, and income or expense derived from the amortization of investment related discounts or premiums, respectively, net of related investment expenses. This item does not include realized or unrealized gains or losses on the sale or holding of investments in debt and equity securities required to be included in earnings for the period or for other than temporary losses related to investments in debt and equity securities which are included in realized losses in the period recognized, and does not include investment income from real or personal property, such as rental income.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 13, 14, 15, 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14, 16 falsefalseInvestment income16false0us-gaap_InterestAndDebtExpenseus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-16900000-16.9falsefalsefalsefalsefalse2truefalsefalse-17900000-17.9falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryInterest and debt related expenses associated with nonoperating financing activities of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 falsefalseInterest expense17false0us-gaap_GainsLossesOnExtinguishmentOfDebtus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse-15300000-15.3falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAmount represents the difference between the fair value of the payments made and the carrying amount of the debt at the time of its extinguishment.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 26 -Paragraph 20, 21 falsefalseCharge for early redemption of debt18false0us-gaap_OtherNonoperatingIncomeExpenseus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse-1200000-1.2falsefalsefalsefalsefalse2truefalsefalse-800000-0.8falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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 falsefalseOther expense19false0us-gaap_NonoperatingIncomeExpenseus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-33300000-33.3falsefalsefalsefalsefalse2truefalsefalse-18600000-18.6falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate amount of income (expense) from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 truefalseTotal other income / (expense), net20false0us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestmentsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse6830000068.3falsefalsefalsefalsefalse2truefalsefalse107400000107.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetarySum 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 truefalseEarnings before income tax21false0us-gaap_IncomeTaxExpenseBenefitus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse2480000024.8falsefalsefalsefalsefalse2truefalsefalse3640000036.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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 falsefalseIncome tax expense22false0us-gaap_ProfitLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse4350000043.5falsefalsefalsefalsefalse2truefalsefalse7100000071.0falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 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 AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) truefalseNet income23true0us-gaap_WeightedAverageNumberOfSharesOutstandingAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseAverage number of common shares outstanding (millions):24false0us-gaap_WeightedAverageNumberOfSharesOutstandingBasicus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse114000000114.0falsefalsefalsefalsefalse2truefalsefalse115600000115.6falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesNumber 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 falsefalseBasic (in shares)25false0us-gaap_WeightedAverageNumberOfDilutedSharesOutstandingus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse114500000114.5falsefalsefalsefalsefalse2truefalsefalse116200000116.2falsefalsefalsefalsefalseSharesxbrli:sharesItemTypesharesThe 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 falsefalseDiluted (in shares)26true0us-gaap_EarningsPerShareAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseEarnings per share of common stock:27false0us-gaap_EarningsPerShareBasicus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse0.380.38falsetruefalsefalsefalse2truefalsefalse0.610.61falsetruefalsefalsefalseEPSus-types:perShareItemTypedecimalThe 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 falsetrueBasic (in dollars per share)28false0us-gaap_EarningsPerShareDilutedus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse0.380.38falsetruefalsefalsefalse2truefalsefalse0.610.61falsetruefalsefalsefalseEPSus-types:perShareItemTypedecimalThe 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 falsetrueDiluted (in dollars per share)29false0us-gaap_CommonStockDividendsPerShareCashPaidus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse0.33250.3325falsetruefalsefalsefalse2truefalsefalse0.30250.3025falsetruefalsefalsefalseEPSus-types:perShareItemTypedecimalAggregate dividends paid 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 falsetrueDividends paid per share of common stock (in dollars per share)30false0natruenanaNo definition available.falsetruefalsefalsefalsefalsefalsefalsefalsefalsehttp://www.dplinc.com/role/statementofincome1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalse3falsefalseUSDtruefalse{dei_LegalEntityAxis} : THE DAYTON POWER AND LIGHT COMPANY 1/1/2011 - 3/31/2011 USD ($) $D2011Q1_SubsidiariesMemberhttp://www.sec.gov/CIK0000787250duration2011-01-01T00:00:002011-03-31T00:00:00falsefalseTHE DAYTON POWER AND LIGHT COMPANYdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$4falsefalseUSDtruefalse{dei_LegalEntityAxis} : THE DAYTON POWER AND LIGHT COMPANY 1/1/2010 - 3/31/2010 USD ($) $D2010Q1_SubsidiariesMemberhttp://www.sec.gov/CIK0000787250duration2010-01-01T00:00:002010-03-31T00:00:00falsefalseTHE DAYTON POWER AND LIGHT COMPANYdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_SubsidiariesMemberdei_LegalEntityAxisexplicitMemberUSDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$OthernaNo definition available.No authoritative reference available.falsefalseTHE DAYTON POWER AND LIGHT COMPANY31false0us-gaap_ElectricUtilityRevenueus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse463800000463.8falsefalsefalsefalsefalse2truefalsefalse438000000438.0falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate revenue, whether regulated or unregulated, derived from the generation, transmission and distribution of electricity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Article 5 falsefalseRevenues32true0us-gaap_CostOfRevenueAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseCost of revenues:33false0us-gaap_FuelCostsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9860000098.6falsefalsefalsefalsefalse2truefalsefalse100600000100.6falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryFuel costs incurred that are directly related to goods produced and sold and services rendered during the reporting period.No authoritative reference available.falsefalseFuel34false0us-gaap_CostOfPurchasedPowerus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse117800000117.8falsefalsefalsefalsefalse2truefalsefalse7260000072.6falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryCost of electricity purchased and sold during the reporting period.No authoritative reference available.falsefalsePurchased power35false0us-gaap_CostOfGoodsSoldElectricus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse216400000216.4falsefalsefalsefalsefalse2truefalsefalse173200000173.2falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryTotal costs related to electricity produced and sold during the reporting period.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 2 -Article 5 truefalseTotal cost of revenues36false0us-gaap_GrossProfitus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse247400000247.4falsefalsefalsefalsefalse2truefalsefalse264800000264.8falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.No authoritative reference available.truefalseGross margin37true0us-gaap_OperatingExpensesAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseOperating expenses:38false0us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperationsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse9140000091.4falsefalsefalsefalsefalse2truefalsefalse7930000079.3falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryDiscloses the amount of operating expense for the period for routine plant maintenance, repairs and operations.No authoritative reference available.falsefalseOperation and maintenance39false0us-gaap_DepreciationDepletionAndAmortizationus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse3310000033.1falsefalsefalsefalsefalse2truefalsefalse3480000034.8falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.No authoritative reference available.falsefalseDepreciation and amortization40false0us-gaap_TaxesExcludingIncomeAndExciseTaxesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse3360000033.6falsefalsefalsefalsefalse2truefalsefalse3230000032.3falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryAll taxes not related to income of the entity or excise or sales taxes levied on the revenue of the entity that are not reported elsewhere. These taxes could include production, real estate, personal property, and pump tax.No authoritative reference available.falsefalseGeneral taxes41false0us-gaap_OperatingExpensesus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse158100000158.1falsefalsefalsefalsefalse2truefalsefalse146400000146.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryGenerally 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.truefalseTotal operating expenses42false0us-gaap_OperatingIncomeLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse8930000089.3falsefalsefalsefalsefalse2truefalsefalse118400000118.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe net result for the period of deducting operating expenses from operating revenues.No authoritative reference available.truefalseOperating income43true0us-gaap_NonoperatingIncomeExpenseAbstractus-gaaptruenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1falsefalsefalse00falsefalsefalsefalsefalse2falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalseOther income / (expense), net:44false0us-gaap_InvestmentIncomeNetus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse6000000.6falsefalsefalsefalsefalse2truefalsefalse5000000.5falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThis item represents investment income derived from investments in debt and equity securities consisting of interest income earned from investments in debt securities and on cash and cash equivalents, dividend income from investments in equity securities, and income or expense derived from the amortization of investment related discounts or premiums, respectively, net of related investment expenses. This item does not include realized or unrealized gains or losses on the sale or holding of investments in debt and equity securities required to be included in earnings for the period or for other than temporary losses related to investments in debt and equity securities which are included in realized losses in the period recognized, and does not include investment income from real or personal property, such as rental income.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name FASB Staff Position (FSP) -Number FAS115-1/124-1 -Paragraph 13, 14, 15, 16 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 115 -Paragraph 14, 16 falsefalseInvestment income45false0us-gaap_InterestAndDebtExpenseus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsetruenegated1truefalsefalse-9700000-9.7falsefalsefalsefalsefalse2truefalsefalse-9400000-9.4falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryInterest and debt related expenses associated with nonoperating financing activities of the entity.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 34 -Paragraph 21 falsefalseInterest expense46false0us-gaap_OtherNonoperatingIncomeExpenseus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse-500000-0.5falsefalsefalsefalsefalse2truefalsefalse-600000-0.6falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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 falsefalseOther expense47false0us-gaap_NonoperatingIncomeExpenseus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse-9600000-9.6falsefalsefalsefalsefalse2truefalsefalse-9500000-9.5falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe aggregate amount of income (expense) from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 truefalseTotal other income / (expense), net48false0us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestmentsus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse7970000079.7falsefalsefalsefalsefalse2truefalsefalse108900000108.9falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetarySum 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 truefalseEarnings before income tax49false0us-gaap_IncomeTaxExpenseBenefitus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse2700000027.0falsefalsefalsefalsefalse2truefalsefalse3680000036.8falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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 falsefalseIncome tax expense50false0us-gaap_ProfitLossus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse5270000052.7falsefalsefalsefalsefalse2truefalsefalse7210000072.1falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph A1, A4, A5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 5 -Subparagraph b Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 29 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 AICPA -Name Accounting Research Bulletin (ARB) -Number 51 -Paragraph 38 -Subparagraph c(1) truefalseNet income51false0us-gaap_PreferredStockDividendsus-gaaptruedebitdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalseterselabel1truefalsefalse2000000.2falsefalsefalsefalsefalse2truefalsefalse2000000.2falsefalsefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryThe 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 falsefalseDividends on preferred stock52false0us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicus-gaaptruecreditdurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalsetotallabel1truefalsefalse5250000052.5falsetruefalsefalsefalse2truefalsefalse7190000071.9falsetruefalsefalsefalseMonetaryxbrli:monetaryItemTypemonetaryNet 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 truefalseEarnings on common stock251CONDENSED CONSOLIDATED STATEMENTS OF RESULTS OF OPERATIONS (USD $)HundredThousandsHundredThousandsNoRoundingUnKnownfalsetrue