Short-term Borrowings (Details) - Schedule of line of credit $ in Millions	12 Months Ended
Dec. 31, 2022 USD ($)
Line of Credit Facility [Line Items]
Outstanding	$ 55.5
Available	84.5
Maximum	140.0
Bank of America [Member]
Line of Credit Facility [Line Items]
Outstanding	15.0
Available	45.0
Maximum	$ 60.0
Credit Type	Uncommitted
Renewal Date	Jan. 25, 2024
PNC Bank [Member]
Line of Credit Facility [Line Items]
Outstanding	$ 39.5
Available	28.5
Maximum	$ 68.0
Credit Type	Committed
Renewal Date	Jan. 31, 2024
CoBank [Member]
Line of Credit Facility [Line Items]
Outstanding	$ 1.0
Available	11.0
Maximum	$ 12.0
Credit Type	Committed
Renewal Date	Nov. 30, 2023

Renewal Date of line of credit.

No definition available.

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Namespace Prefix:	msex_
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Balance Type:	na
Period Type:	duration

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Information about borrowings which initially required repayment in less than twelve months (or normal operating cycle, if longer) after its issuance and that does not otherwise qualify as long-term debt. It typically is comprised of borrowings under letters of credit, lines of credit, commercial paper, and notes payable of short duration. Disclosures include amounts of borrowings under each arrangement, description of underlying arrangements, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements such as the effects of refinancings and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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Period Type:	duration

- Details

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Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=msex_PncBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: