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v2.4.1.9

Rate and Regulatory Matters (Schedule of Regulatory Assets) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 66,216 us-gaap_RegulatoryAssets | $ 34,386 us-gaap_RegulatoryAssets
Retirement Benefits [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | 47,868 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = us-gaap_PensionCostsMember | 20,826 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = us-gaap_PensionCostsMember
Remaining recovery period | Various |
Income Taxes [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | 17,195 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = msex_IncomeTaxesMember | 12,207 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = msex_IncomeTaxesMember
Remaining recovery period | Various |
Rate Cases, Tank Painting, and Other [Member] |  |
Regulatory Assets [Line Items] |  |
Regulatory Assets | $ 1,153 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = msex_RateCasesStormCostsTankPaintingOtherMember | $ 1,353 us-gaap_RegulatoryAssets / us-gaap_RegulatoryAssetAxis = msex_RateCasesStormCostsTankPaintingOtherMember
Remaining recovery period | 2-9 years |

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- Definition The period remaining for recovery of costs in the rates we charge customers. + References No definition available. + Details
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- 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
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