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Organization (Details) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2022 USD ($) business_segments	Mar. 31, 2021 USD ($)	Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Restructuring	$ 2.1	$ 2.2	$ 2.1	$ 2.2	$ 3.1	$ 2.8
Restructuring and other charges	0.6	0.8	3.0	2.2
Payments			2.6	1.6
Pension costs (benefits) other then service	$ (1.0)	$ (0.8)	$ (2.0)	$ (1.6)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	21.00%	21.00%
Number of Reportable Segments | business_segments	2
Proceeds from Other Equity, Gross Amount	$ 4.8		$ 4.8
Intercompany Loan related to NMTC	12.2		12.2
Investment Fund Contribution for NMTC	16.5		16.5
Sub-CDE loan from NMTC	16.2		16.2
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges	$ 0.0	$ 0.0	$ 0.0	$ 0.1

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