XML 52 R37.htm IDEA: XBRL DOCUMENT
v3.24.0.1

Components of Energy Supply Obligations (Detail) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | ---
Contractual Obligation [Line Items] |  |
Energy Supply Obligations-Current | $ 15.0 | $ 24.1
Renewable Energy Portfolio Standards |  |
Contractual Obligation [Line Items] |  |
Energy Supply Obligations-Current | 6.4 | 7.8
Exchange Gas Obligation |  |
Contractual Obligation [Line Items] |  |
Energy Supply Obligations-Current | $ 8.6 | $ 16.3

X
- Definition Current liabilities attributable to energy marketing activities (trading activities). Current energy marketing (trading activities) are when entities engage in both financial and physical trading to increase profits, manage their commodity price risk and enhance system reliability. They may trade electricity, coal, natural gas and oil. These entities typically use a variety of financial instruments, including forward contracts, options and swaps. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
Name: | us-gaap_EnergyMarketingContractLiabilitiesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Contractual Obligation [Line Items] + References No definition available. + Details
Name: | utl_ContractualObligationLineItems
Namespace Prefix: | utl_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_RegulatoryLiabilityAxis=utl_RenewableEnergyPortfolioRequirementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByLiabilityClassAxis=us-gaap_ObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |