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v3.21.2

Segment Information (Narrative) (Details) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2021 USD ($) business_segments | Sep. 30, 2020 USD ($) | Sep. 30, 2019
Segment Reporting [Abstract] |  |  |
Number of Reportable Segments | business_segments | 2 |  |
Revenue, Major Customer [Line Items] |  |  |
Receivables, net | $ 212.2 | $ 180.8 |
Intangible Assets, Net (Including Goodwill) | 507.6 | 508.7 |
Total assets | $ 1,518.0 | 1,395.0 |
Document Period End Date | Sep. 30, 2021 |  |
Mueller Co. [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Intangible Assets, Net (Including Goodwill) | $ 473.2 | 490.8 |
Mueller Technologies [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
Intangible Assets, Net (Including Goodwill) | $ 34.4 | $ 17.9 |
Customer Concentration Risk [Member] | Major Customers, Group One | Sales Revenue, Goods, Gross [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 58.00% | 53.00% | 53.00%
Customer Concentration Risk [Member] | Major Customers, Group Two | Sales Revenue, Goods, Gross [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 37.00% | 34.00% | 34.00%
Customer Concentration Risk [Member] | Ferguson Enterprises | Sales Revenue, Goods, Gross [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 19.00% | 17.00% | 18.00%
Customer Concentration Risk [Member] | Ferguson Enterprises | Sales Revenue, Goods, Gross [Member] | Mueller Co. [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 18.00% | 16.00% | 17.00%
Customer Concentration Risk [Member] | Ferguson Enterprises | Sales Revenue, Goods, Gross [Member] | Mueller Technologies [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 33.00% | 22.00% | 30.00%
Customer Concentration Risk [Member] | HDS IP Holdings, LLC [Member] | Sales Revenue, Goods, Gross [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 18.00% | 17.00% | 16.00%
Customer Concentration Risk [Member] | HDS IP Holdings, LLC [Member] | Sales Revenue, Goods, Gross [Member] | Mueller Co. [Member] |  |  |
Revenue, Major Customer [Line Items] |  |  |
10 largest customers | 20.00% | 19.00% | 18.00%

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