XML 62 R48.htm IDEA: XBRL DOCUMENT
v3.19.1

Company's Liability for Environmental Obligations (Detail) - USD ($) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2019 | Mar. 31, 2018 | Mar. 31, 2019 | Mar. 31, 2018
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of Period | $ 2.0 | $ 2.1 |  |
Additions | 0.1 | 0.2 |  |
Less: Payments / Reductions | 0.1 | 0.2 |  |
Total Balance at End of Period | 2.0 | 2.1 |  |
Less: Current Portion |  |  | $ 0.6 | $ 0.6
Noncurrent Balance |  |  | 1.4 | 1.5
Total Balance at End of period | 2.0 | 2.1 | 2.0 | 2.1
Fitchburg Gas and Electric Light Company |  |  |  |
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of Period |  | 0.1 |  |
Additions |  | 0.1 |  |
Less: Payments / Reductions |  | 0.1 |  |
Total Balance at End of Period |  | 0.1 |  |
Less: Current Portion |  |  |  | 0.1
Total Balance at End of period |  | 0.1 |  | 0.1
Northern Utilities Inc |  |  |  |
Environmental Exit Cost [Line Items] |  |  |  |
Total Balance at Beginning of Period | 2.0 | 2.0 |  |
Additions | 0.1 | 0.1 |  |
Less: Payments / Reductions | 0.1 | 0.1 |  |
Total Balance at End of Period | 2.0 | 2.0 |  |
Less: Current Portion |  |  | 0.6 | 0.5
Noncurrent Balance |  |  | 1.4 | 1.5
Total Balance at End of period | $ 2.0 | $ 2.0 | $ 2.0 | $ 2.0

X
- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingencies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense for newly incurred environmental loss contingencies. Includes, but is not limited to, remediation expense and interest accretion. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingenciesChargesToExpenseForNewLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of cash outflow to settle environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q1) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 17 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3367-108585 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingenciesPayments1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable in twelve months or in the next operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.20) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6911-107765 + Details
Name: | us-gaap_AccruedEnvironmentalLossContingenciesCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value of the obligation (known or estimated) arising from requirements to perform activities to remediate one or more sites, payable after twelve months or beyond the next operating cycle if longer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.24) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 10 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13237-110859 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 + Details
Name: | us-gaap_AccruedEnvironmentalLossContingenciesNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_EnvironmentalExitCostLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=utl_FitchburgGasAndElectricLightCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=utl_NorthernUtilitiesIncMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |