XML 26 R33.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Regulatory Liabilities (Detail) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
--- | --- | ---
Regulatory Liabilities [Line Items] |  |
Regulatory Liabilities | $ 8.7 us-gaap_RegulatoryLiabilities | $ 9.7 us-gaap_RegulatoryLiabilities
Regulatory Tracker Mechanisms |  |
Regulatory Liabilities [Line Items] |  |
Regulatory Liabilities | $ 8.7 us-gaap_RegulatoryLiabilities / us-gaap_RegulatoryLiabilityAxis = utl_RegulatoryTrackerMechanismsMember | $ 9.7 us-gaap_RegulatoryLiabilities / us-gaap_RegulatoryLiabilityAxis = utl_RegulatoryTrackerMechanismsMember

X
- Definition The amount for the individual regulatory liability as itemized in a table of regulatory liabilities as of the end of the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 405 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6500807&loc=d3e48068-110394 + Details
Name: | us-gaap_RegulatoryLiabilities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryLiabilitiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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