XML 53 R45.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Details on Long Term Debt (Parenthetical) (Detail) | Dec. 31, 2014 | Dec. 31, 2013
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6.33% Notes, Due May 1, 2022 |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.33%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSixPointThreeThreePercentDueMayOneTwentyTwentyTwoMember | 6.33%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSixPointThreeThreePercentDueMayOneTwentyTwentyTwoMember
First Mortgage Bonds 5.24% Series, Due March 2, 2020 | Unitil Energy Systems Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 5.24%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsFivePointTwoFourPercentDueMarchTwoTwentyTwentyMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember | 5.24%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsFivePointTwoFourPercentDueMarchTwoTwentyTwentyMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember
First Mortgage Bonds 8.49% Series, Due October 14, 2024 | Unitil Energy Systems Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 8.49%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsEightPointFourNinePercentDueOctoberFourteenTwentyTwentyFourMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember | 8.49%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsEightPointFourNinePercentDueOctoberFourteenTwentyTwentyFourMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember
First Mortgage Bonds 6.96% Series, Due September 1, 2028 | Unitil Energy Systems Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.96%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsSixPointNineSixPercentDueSeptemberOneTwentyTwentyEightMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember | 6.96%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsSixPointNineSixPercentDueSeptemberOneTwentyTwentyEightMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember
First Mortgage Bonds 8.00% Series, Due May 1, 2031 | Unitil Energy Systems Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsEightPointZeroZeroPercentDueMayOneTwentyThirtyOneMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember | 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsEightPointZeroZeroPercentDueMayOneTwentyThirtyOneMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember
First Mortgage Bonds 6.32% Series, Due September 15, 2036 | Unitil Energy Systems Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.32%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsSixPointThreeTwoPercentDueSeptemberFifteenTwentyThirtySixMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember | 6.32%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_FirstMortgageBondsSixPointThreeTwoPercentDueSeptemberFifteenTwentyThirtySixMember / dei_LegalEntityAxis = utl_UnitilEnergySystemsIncMember
6.75% Notes, Due November 30, 2023 | Fitchburg Gas and Electric Light Company |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSixPointSevenFivePercentDueNovemberThirtyTwentyTwentyThreeMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember | 6.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSixPointSevenFivePercentDueNovemberThirtyTwentyTwentyThreeMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember
7.37% Notes, Due January 15, 2029 | Fitchburg Gas and Electric Light Company |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 7.37%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSevenPointThreeSevenPercentDueJanuaryFifteenTwentyTwentyNineMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember | 7.37%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSevenPointThreeSevenPercentDueJanuaryFifteenTwentyTwentyNineMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember
7.98% Notes, Due June 1, 2031 | Fitchburg Gas and Electric Light Company |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 7.98%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSevenPointNineEightPercentDueJuneOneTwentyThirtyOneMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember | 7.98%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSevenPointNineEightPercentDueJuneOneTwentyThirtyOneMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember
6.79% Notes, Due October 15, 2025 | Fitchburg Gas and Electric Light Company |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.79%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSixPointSevenNinePercentDueOctoberFifteenTwentyTwentyFiveMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember | 6.79%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesSixPointSevenNinePercentDueOctoberFifteenTwentyTwentyFiveMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember
5.90% Notes, Due December 15, 2030 | Fitchburg Gas and Electric Light Company |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 5.90%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesFivePointNineZeroPercentDueDecemberFifteenTwentyThirtyMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember | 5.90%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_NotesFivePointNineZeroPercentDueDecemberFifteenTwentyThirtyMember / dei_LegalEntityAxis = utl_FitchburgGasAndElectricLightCompanyMember
6.95% Senior Notes, Series A, Due December 3, 2018 | Northern Utilities Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 6.95%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSixPointNineFivePercentDueDecemberThreeTwentyEighteenMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember | 6.95%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSixPointNineFivePercentDueDecemberThreeTwentyEighteenMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember
5.29% Senior Notes, Due March 2, 2020 | Northern Utilities Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 5.29%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesFivePointTwoNinePercentDueMarchTwoTwentyTwentyMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember | 5.29%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesFivePointTwoNinePercentDueMarchTwoTwentyTwentyMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember
7.72% Senior Notes, Series B, Due December 3, 2038 | Northern Utilities Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 7.72%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSevenPointSevenTwoPercentDueDecemberThreeTwentyThirtyEightMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember | 7.72%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSevenPointSevenTwoPercentDueDecemberThreeTwentyThirtyEightMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember
4.42% Senior Notes, Due October 15, 2044 | Northern Utilities Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 4.42%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesFourPointFourTwoPercentDueOctoberFifteenTwentyFortyFourMember / dei_LegalEntityAxis = utl_NorthernUtilitiesIncMember |
7.15% Senior Notes, Due December 15, 2018 | Granite State Gas Transmission Inc |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 7.15%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSevenPointOneFivePercentDueDecemberFifteenTwentyEighteenMember / dei_LegalEntityAxis = utl_GraniteStateGasTransmissionIncMember | 7.15%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorNotesSevenPointOneFivePercentDueDecemberFifteenTwentyEighteenMember / dei_LegalEntityAxis = utl_GraniteStateGasTransmissionIncMember
8.00% Senior Secured Notes, Due August 1, 2017 | Unitil Realty Corp |  |
Debt Instrument [Line Items] |  |
Stated interest rate | 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorSecuredNotesEightPointZeroZeroPercentDueThroughAugustOneTwentySeventeenMember / dei_LegalEntityAxis = utl_UnitilRealtyCorpMember | 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_DebtInstrumentAxis = utl_SeniorSecuredNotesEightPointZeroZeroPercentDueThroughAugustOneTwentySeventeenMember / dei_LegalEntityAxis = utl_UnitilRealtyCorpMember

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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