XML 21 R7.htm IDEA: XBRL DOCUMENT
v3.21.1

CONDENSED CONSOLIDATED STATEMENTS OF CAPITAL STOCK AND LONG-TERM DEBT (Unaudited) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Common Stock, No Par Value | $ 217,976 | $ 217,451
Retained Earnings | 130,872 | 128,757
TOTAL COMMON EQUITY | 348,848 | 346,208
TOTAL PREFERRED STOCK | 2,084 | 2,084
SUBTOTAL LONG-TERM DEBT | 276,605 | 277,241
Add: Premium on Issuance of Long-term Debt | 7,569 | 7,669
Less: Unamortized Debt Expense | (4,351) | (4,411)
Less: Current Portion of Long-term Debt | (7,159) | (7,255)
TOTAL LONG-TERM DEBT | 272,664 | 273,244
Amortizing Secured Note, due December 20, 2021 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 255 | 336
Amortizing Secured Note, due May 19, 2028 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 3,010 | 3,115
Amortizing Secured Note, due August 25, 2030 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 2,637 | 2,707
Amortizing Secured Note, due September 19, 2031 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 2,917 | 2,987
State Revolving Trust Note, due December 31, 2022 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 119 | 119
State Revolving Trust Note, due May 1, 2025 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,170 | 1,170
State Revolving Trust Note, due March 1, 2026 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 243 | 266
State Revolving Trust Note, due January 25, 2027 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 286 | 307
State Revolving Trust Note, due December 1, 2026 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 390 | 389
State Revolving Trust Bond 0.00%, due August 1, 2021 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 10 | 11
State Revolving Trust Note, due July 1, 2028 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 192 | 192
State Revolving Trust Note, due January 1, 2028 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 62 | 62
State Revolving Trust Note, due August 1, 2031 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 763 | 793
Amortizing Secured Note, due April 20, 2029 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 2,819 | 2,907
Amortizing Secured Note 7.05%, due January 20, 2030 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 2,208 | 2,271
Amortizing Secured Note 5.69%, due January 20, 2030 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 4,530 | 4,658
Amortizing Secured Note, due April 20, 2040 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 8,397 | 8,506
Amortizing Secured Note, due April 20, 2040 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 3,116 | 3,156
State Revolving Trust Note, due July 1, 2031 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,699 | 1,699
State Revolving Trust Note, due February 1, 2036 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 934 | 961
State Revolving Trust Note, due November 1, 2038 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,543 | 1,543
State Revolving Trust Note, due November 30, 2030 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 883 | 883
Construction Loans [Member] |  |
SUBTOTAL LONG-TERM DEBT | 51,223 | 50,536
First Mortgage Bonds - Series BB [Member] |  |
SUBTOTAL LONG-TERM DEBT | 116 | 119
First Mortgage Bonds - Series CC [Member] |  |
SUBTOTAL LONG-TERM DEBT | 164 | 164
First Mortgage Bonds - Series EE [Member] |  |
SUBTOTAL LONG-TERM DEBT | 996 | 1,036
First Mortgage Bonds - Series FF [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,870 | 1,870
First Mortgage Bonds - Series GG [Member] |  |
SUBTOTAL LONG-TERM DEBT | 531 | 541
First Mortgage Bonds - Series HH [Member] |  |
SUBTOTAL LONG-TERM DEBT | 620 | 620
First Mortgage Bonds - Series II [Member] |  |
SUBTOTAL LONG-TERM DEBT | 326 | 338
First Mortgage Bonds - Series JJ [Member] |  |
SUBTOTAL LONG-TERM DEBT | 500 | 500
First Mortgage Bonds - Series KK [Member] |  |
SUBTOTAL LONG-TERM DEBT | 704 | 719
First Mortgage Bonds - Series LL [Member] |  |
SUBTOTAL LONG-TERM DEBT | 846 | 846
First Mortgage Bonds - Series MM [Member] |  |
SUBTOTAL LONG-TERM DEBT | 903 | 937
First Mortgage Bonds - Series NN [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,105 | 1,105
First Mortgage Bonds - Series OO [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,605 | 1,656
First Mortgage Bonds - Series PP [Member] |  |
SUBTOTAL LONG-TERM DEBT | 600 | 600
First Mortgage Bonds - Series QQ [Member] |  |
SUBTOTAL LONG-TERM DEBT | 9,915 | 9,915
First Mortgage Bonds - Series RR [Member] |  |
SUBTOTAL LONG-TERM DEBT | 22,500 | 22,500
First Mortgage Bonds - Series SS [Member] |  |
SUBTOTAL LONG-TERM DEBT | 23,000 | 23,000
First Mortgage Bonds - Series TT [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,756 | 1,806
First Mortgage Bonds - Series UU [Member] |  |
SUBTOTAL LONG-TERM DEBT | 705 | 705
First Mortgage Bonds - Series VV [Member] |  |
SUBTOTAL LONG-TERM DEBT | 1,813 | 1,861
First Mortgage Bonds - Series WW [Member] |  |
SUBTOTAL LONG-TERM DEBT | 715 | 715
First Mortgage Bonds - Series XX [Member] |  |
SUBTOTAL LONG-TERM DEBT | 10,121 | 10,247
First Mortgage Bonds - Series YY [Member] |  |
SUBTOTAL LONG-TERM DEBT | 3,710 | 3,710
0.00%, Series 2018A, due August 1, 2047 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 6,167 | 6,246
3.00%-5.00%, Series 2018B, due August 1, 2047 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 2,211 | 2,211
4.00%, Series 2019A, due August 1, 2059 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 32,500 | 32,500
5.00%, Series 2019B, due August 1, 2059 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 21,200 | 21,200
2.90%, Series 2020A, due November 18, 2050 [Member] |  |
SUBTOTAL LONG-TERM DEBT | 40,000 | 40,000
Convertible Preferred Stock $7.00 Series [Member] |  |
TOTAL PREFERRED STOCK | 1,005 | 1,005
Nonredeemable Preferred Stock $7.00 Series [Member] |  |
TOTAL PREFERRED STOCK | 79 | 79
Nonredeemable Preferred Stock $4.75 Series [Member] |  |
TOTAL PREFERRED STOCK | $ 1,000 | $ 1,000

X
- Definition Refers to total equity attributable to common stockholders. + References No definition available. + Details
Name: | msex_TotalCommonEquity
Namespace Prefix: | msex_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Aggregate par or stated value of issued nonredeemable common stock (or common stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable common shares, par value and other disclosure concepts are in another section within stockholders' equity. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 852 -SubTopic 10 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766 Reference 2: 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(29)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_CommonStockValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after accumulated amortization, of debt discount. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 + Details
Name: | us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after accumulated amortization, of debt premium. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 1A -URI http://asc.fasb.org/extlink&oid=124435984&loc=d3e28541-108399 + Details
Name: | us-gaap_DebtInstrumentUnamortizedPremium
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1D -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611 Reference 7: 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(22)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.19,20) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + 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 210.5-02.22) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_LongTermDebtNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Aggregate par or stated value of issued nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer). This item includes treasury stock repurchased by the entity. Note: elements for number of nonredeemable preferred shares, par value and other disclosure concepts are in another section within stockholders' equity. + 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(28)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 852 -SubTopic 10 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766 + Details
Name: | us-gaap_PreferredStockValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The cumulative amount of the reporting entity's undistributed earnings or deficit. + 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(30)(a)(3)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 852 -SubTopic 10 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 65 -Paragraph 15 -Subparagraph (g)(2) -URI http://asc.fasb.org/extlink&oid=121322162&loc=SL121327923-165333 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(a)(4)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 65 -Paragraph 2 -Subparagraph (h)(2) -URI http://asc.fasb.org/extlink&oid=124501264&loc=SL117420844-207641 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 65 -Paragraph 2 -Subparagraph (g)(2)(i) -URI http://asc.fasb.org/extlink&oid=124501264&loc=SL117420844-207641 + Details
Name: | us-gaap_RetainedEarningsAccumulatedDeficit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebtZeroMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNoteMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote9Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustBond1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote4Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote5Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote6Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt4Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt5Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt6Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt7Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_SecuredDebt8Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote7Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote10Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote11Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_StateRevolvingTrustNote8Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_NewConstructionLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage5Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage6Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage8Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage9Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage10Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage11Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage12Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage13Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage14Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage15Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage16Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage17Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage18Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage19Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage20Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage21Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage22Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage23Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage24Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage25Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage26Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage27Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage28Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage29Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage31Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage32Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage33Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=msex_FirstMortgage34Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_ConvertiblePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=us-gaap_NonredeemablePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=msex_NonredeemablePreferredStock1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |