Organization (Details) $ in Millions	3 Months Ended
	Dec. 31, 2021 USD ($) business_segments	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)
Segment Reporting Information [Line Items]
Restructuring	$ 3.0	$ 1.9	$ 3.1	$ 2.8
Restructuring and other charges	2.4	1.4
Payments	1.3	1.1
Pension costs (benefits) other then service	$ (1.0)	$ (0.8)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%
Number of Reportable Segments | business_segments	2
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
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges	$ 0.0	$ 0.1