XML 22 R48.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Retirement Benefit Obligations - Additional Information (Detail) (USD $) | 9 Months Ended
--- | ---
Sep. 30, 2013
Pension Plan |
Defined Benefit Plan Disclosure [Line Items] |
Contributions to benefit plan | $ 3,700,000
Other Postretirement Benefit Plans, Defined Benefit |
Defined Benefit Plan Disclosure [Line Items] |
Contributions to benefit plan | 2,500,000
Supplemental Employee Retirement Plans, Defined Benefit |
Defined Benefit Plan Disclosure [Line Items] |
Contributions to benefit plan | 40,000
Expected additional contribution to SERP plan | $ 13,000

X
- Definition The increase in the fair value of plan assets from contributions made by the employer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition Defined Benefit Plan, Estimated Additional Employer Contributions in Remainder Of Fiscal Year + References No definition available. + Details
Name: | utl_DefinedBenefitPlanEstimatedAdditionalEmployerContributionsInRemainderOfFiscalYear
Namespace Prefix: | utl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant