XML 48 R33.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Rate and Regulatory Matters (Schedule of Regulatory Assets) (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2015 | Dec. 31, 2014
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 58,552 | $ 66,216
Retirement Benefits [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 39,378 | 47,868
Remaining recovery period | Various |
Income Taxes [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 15,541 | 17,195
Remaining recovery period | Various |
Rate Cases, Tank Painting, and Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 3,633 | $ 1,153
Remaining recovery period | 2-9 years |

X
- Definition The period remaining for recovery of costs in the rates we charge customers. + References No definition available. + Details
Name: | msex_RemainingRecoveryPeriod
Namespace Prefix: | msex_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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_RegulatoryAssetLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount for the individual regulatory asset as itemized in a table of regulatory assets 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 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
Name: | us-gaap_RegulatoryAssets
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=us-gaap_PensionCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=msex_IncomeTaxesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RegulatoryAssetAxis=msex_RateCasesStormCostsTankPaintingOtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |