XML 56 R42.htm IDEA: XBRL DOCUMENT
v3.25.3

Organization (Details) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2025 USD ($) employee business_segments
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Number of Reportable Segments | business_segments | 2
Entity Number of Employees | employee | 3,500
Percentage of Employees Covered by Collective Bargaining Agreements | 0.42
Proceeds From Other Equity, Gross Amount | $ 4.8
Intercompany Loan Related to NMTC | 12.2
Investment Fund Contribution For NMTC | 16.5
Sub CDE Loan From NMTC | 16.2
Other Sundry Liabilities, Noncurrent | $ 3.9

X
- Definition Number of persons employed by the Entity + References No definition available. + Details
Name: | dei_EntityNumberOfEmployees
Namespace Prefix: | dei_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

X
- Definition Intercompany Loan Related to NMTC + References No definition available. + Details
Name: | mwa_IntercompanyLoanRelatedToNMTC
Namespace Prefix: | mwa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Investment Fund Contribution For NMTC + References No definition available. + Details
Name: | mwa_InvestmentFundContributionForNMTC
Namespace Prefix: | mwa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Percentage of Employees Covered by Collective Bargaining Agreements + References No definition available. + Details
Name: | mwa_PercentageOfEmployeesCoveredByCollectiveBargainingAgreements
Namespace Prefix: | mwa_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Definition Proceeds From Other Equity, Gross Amount + References No definition available. + Details
Name: | mwa_ProceedsFromOtherEquityGrossAmount
Namespace Prefix: | mwa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Sub CDE Loan From NMTC + References No definition available. + Details
Name: | mwa_SubCDELoanFromNMTC
Namespace Prefix: | mwa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 47 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-47 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 54 -Subparagraph (e) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482785/280-10-55-54 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 280 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 18 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482810/280-10-50-18 + Details
Name: | us-gaap_NumberOfReportableSegments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Obligations not otherwise itemized or categorized in the footnotes to the financial statements that are expected to be paid after one year (or the normal operating cycle, if longer), from the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 210 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(24)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(15)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1 + Details
Name: | us-gaap_OtherSundryLiabilitiesNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant