XML 43 R29.htm IDEA: XBRL DOCUMENT
v3.25.3

Summary of Significant Accounting Policies (Tables) | 12 Months Ended
--- | ---
Sep. 30, 2025
Accounting Policies [Abstract] |
Financing Receivable, Current, Allowance for Credit Loss [Table Text Block] | The following table summarizes information concerning our allowance for credit losses:
| 2025 |  | 2024 |  | 2023
| (in millions)
Balance at beginning of year | $ | 8.3 |  |  | $ | 7.3 |  |  | $ | 5.6 |
Provision charged to expense | 0.2 |  |  | 2.7 |  |  | 1.9 |
Write-offs and other | (4.9) |  |  | (1.7) |  |  | (0.2) |
Balance at end of year | $ | 3.6 |  |  | $ | 8.3 |  |  | $ | 7.3 |
Schedule of Reserves for Excess and Obsolete Inventory | The following table summarizes information concerning our inventory valuation reserves:
| 2025 |  | 2024 |  | 2023
| (in millions)
Balance at beginning of year | $ | 21.4 |  |  | $ | 16.8 |  |  | $ | 16.5 |
Provision charged to expense | 11.9 |  |  | 13.3 |  |  | 3.8 |
Inventory disposed | (9.9) |  |  | (8.7) |  |  | (3.5) |
Balance at end of year | $ | 23.4 |  |  | $ | 21.4 |  |  | $ | 16.8 |
Schedule of Product Warranty Liability | Activity in our accrued warranty, reported within Other current liabilities and Other noncurrent liabilities, is presented below:
| 2025 |  | 2024 |  | 2023
| (in millions)
Balance at beginning of year | $ | 23.6 |  |  | $ | 15.7 |  |  | $ | 10.7 |
Provision charged to expense | 14.9 |  |  | 13.0 |  |  | 14.8 |
Warranty utilization | (12.9) |  |  | (5.1) |  |  | (9.8) |
Balance at end of year | $ | 25.6 |  |  | $ | 23.6 |  |  | $ | 15.7 |

X
- Definition Schedule of Reserves for Excess and Obsolete Inventory [Table Text Block] + References No definition available. + Details
Name: | mwa_ScheduleOfReservesForExcessAndObsoleteInventoryTableTextBlock
Namespace Prefix: | mwa_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Tabular disclosure of allowance for credit loss of financing receivable, classified as current. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org/1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_ScheduleOfCreditLossesForFinancingReceivablesCurrentTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the changes in the guarantor's aggregate product warranty liability, including the beginning balance of the aggregate product warranty liability, the aggregate reductions in that liability for payments made (in cash or in kind) under the warranty, the aggregate changes in the liability for accruals related to product warranties issued during the reporting period, the aggregate changes in the liability for accruals related to preexisting warranties (including adjustments related to changes in estimates), and the ending balance of the aggregate product warranty liability. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 460 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 8 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482425/460-10-50-8 + Details
Name: | us-gaap_ScheduleOfProductWarrantyLiabilityTableTextBlock
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:textBlockItemType
Balance Type: | na
Period Type: | duration