XML 31 R44.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Regulatory Matters - Additional Information (Detail) (USD $) | 0 Months Ended | 9 Months Ended |  | 0 Months Ended | 9 Months Ended | 0 Months Ended | 9 Months Ended | 0 Months Ended | 9 Months Ended |  | 0 Months Ended |  | 0 Months Ended | 1 Months Ended | 9 Months Ended | 0 Months Ended | 1 Months Ended | 0 Months Ended | 9 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Apr. 21, 2014 Northern Utilities Inc | Feb. 28, 2014 Northern Utilities Inc | Dec. 27, 2013 Northern Utilities Inc | Sep. 30, 2014 Northern Utilities Inc | Dec. 27, 2013 Northern Utilities Inc | Apr. 21, 2014 Northern Utilities Inc New Hampshire | Sep. 30, 2014 Northern Utilities Inc New Hampshire | Apr. 21, 2014 Northern Utilities Inc New Hampshire Natural Gas Distribution | Dec. 27, 2013 Northern Utilities Inc Maine | Sep. 30, 2014 Northern Utilities Inc Maine | Apr. 30, 2014 Unitil Energy Systems Inc | Sep. 30, 2014 Unitil Energy Systems Inc | Apr. 25, 2013 Unitil Energy Systems Inc | Apr. 25, 2013 Unitil Energy Systems Inc Storm Costs | Apr. 25, 2013 Unitil Energy Systems Inc Storm Costs | May 30, 2014 Fitchburg Gas and Electric Light Company | Jul. 31, 2013 Fitchburg Gas and Electric Light Company | Sep. 30, 2014 Fitchburg Gas and Electric Light Company | May 30, 2014 Fitchburg Gas and Electric Light Company Storm Costs | Jul. 31, 2013 Fitchburg Gas and Electric Light Company Storm Costs | Jun. 27, 2014 Granite State Gas Transmission Inc Gas Transportation and Storage | Sep. 30, 2014 Granite State Gas Transmission Inc Gas Transportation and Storage
Regulatory Matters [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Increase in annual revenue | $ 1,400,000 |  |  | $ 1,000,000 |  | $ 1,400,000 |  | $ 4,600,000 | $ 3,800,000 |  |  |  |  |  |  | $ 5,600,000 | $ 6,700,000 |  |  |  |  |
Amendment effective date |  |  |  | May 1, 2014 |  |  | May 1, 2015 |  |  | January 1, 2014 |  | May 1, 2014 |  |  |  |  |  | June 1, 2014 |  |  |  | August 1, 2014
TIRA initial term |  |  |  | Four years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of eligibility for earnings | 10.00% |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of earnings shared equally | 11.00% |  | 11.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service quality plan penalties imposed |  |  |  |  | 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First annual TIRA Adjustment |  | 1,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First annual TIRA Adjustment, effective date |  |  |  | May 1, 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of increase in annual revenue |  |  |  |  |  | 9.50% |  |  |  |  |  |  |  |  |  | 9.50% |  |  |  |  |  |
Adjustment to recover the increased spending for vegetation management program and reliability enhancement program and a proposed storm resiliency program |  |  |  |  |  |  |  |  |  |  | 1,500,000 |  |  |  |  |  |  |  |  |  |  |
Settlement agreement date |  |  |  |  |  |  |  |  |  |  | May 01, 2016 |  |  |  |  |  |  |  |  |  |  |
Annual revenue increase in rate adjustments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 600,000 |
Percentage of approved return on equity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.70% |  |  |  |  |
Percentage of approved common equity ratio |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 48.00% |  |  |  |  |
Cost recovery period, years |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  | 5 years |  | 3 years | 3 years |  |
Deferred emergency storm repair costs incurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,000,000 |  |
Annual funding amount approved |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 500,000 |  |  |  |  |
Recovery amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,300,000 |  | 900,000 |  |  |  |  |
Storm expenditures |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,000,000 |  |  |
Interest rate allowed by regulators on the unrecovered amount of storm costs which have been approved for recovery through rate adjustments |  |  |  |  |  |  |  |  |  |  |  |  | 4.52% |  |  |  |  |  |  |  |  |

X
- Definition Carrying amount as of the balance sheet date of the portion of the reserved funds established by a utility from customer payments to cover the repair costs of damages from major storms, which repairs are expected to be incurred beyond one year or the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499739&loc=d3e43603-110378 + Details
Name: | us-gaap_AssetRecoveryDamagedPropertyCostsNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of capitalized storm costs of a regulated entity that are expected to be recoverable through rate adjustments after one year or beyond the normal operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499739&loc=d3e43603-110378 + Details
Name: | us-gaap_DeferredStormAndPropertyReserveDeficiencyNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The increase (decrease) during the reporting period in unrecovered fuel costs for a regulated utility company. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
Name: | us-gaap_IncreaseDecreaseInRegulatoryClauseRevenue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Total increase in earnings in the period representing the cost of equity (based on assumed rate of return) and/or borrowed funds (based on interest rate) used to finance construction of regulated assets, which is expected to be recovered through rate adjustments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 360 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500269&loc=d3e45485-110386 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44278-110382 + Details
Name: | us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage of public utility's approved equity to capital, including debt and equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedEquityCapitalStructurePercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of public utility's approved return on equity. + References No definition available. + Details
Name: | us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Describes the term of the registration payment arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6449706&loc=d3e16207-108621 + Details
Name: | us-gaap_RegistrationPaymentArrangementTerm
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Remaining recovery period of regulatory assets for which no return on investment during recovery period is provided, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 55 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6591318&loc=d3e44360-110383 + Details
Name: | us-gaap_RemainingRecoveryPeriodOfRegulatoryAssetsForWhichNoReturnOnInvestmentDuringRecoveryPeriodIsProvided1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Adjustment for rate Increase. + References No definition available. + Details
Name: | utl_AdjustmentForRateIncrease
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Effective date of rates resulting from rate case. + References No definition available. + Details
Name: | utl_AmendmentEffectiveDate
Namespace Prefix: | utl_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Effective Date + References No definition available. + Details
Name: | utl_EffectiveDate
Namespace Prefix: | utl_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Increase in annual revenue allowed as a result of a rate case filing. + References No definition available. + Details
Name: | utl_IncreaseDecreaseInUnearnedRevenue
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Infrastructure Replacement Adjustment + References No definition available. + Details
Name: | utl_InfrastructureReplacementAdjustment
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the interest rate allowed by regulators on the unrecovered amount of storm costs which have been approved for recovery through rate adjustments. + References No definition available. + Details
Name: | utl_InterestRateAllowedOnUnrecoveredStormCosts
Namespace Prefix: | utl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Penalty For Non Fulfillment Of Commitment. + References No definition available. + Details
Name: | utl_PenaltyForNonFulfillmentOfCommitment
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Percentage Of Earnings Distributed. + References No definition available. + Details
Name: | utl_PercentageOfEarningsDistributed
Namespace Prefix: | utl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Return. + References No definition available. + Details
Name: | utl_PercentageOfReturn
Namespace Prefix: | utl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage Of Revenue Increase. + References No definition available. + Details
Name: | utl_PercentageOfRevenueIncrease
Namespace Prefix: | utl_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | utl_RegulatoryMattersLineItems
Namespace Prefix: | utl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Settlement Dates. + References No definition available. + Details
Name: | utl_SettlementDates
Namespace Prefix: | utl_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Expenditures related to specific storms. + References No definition available. + Details
Name: | utl_StormExpenditures
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration