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Organization Restructuring (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost and Reserve [Line Items]
Beginning balance			$ 1.7	$ 0.9
Restructuring and other charges	$ 8.6	$ 2.5	11.9	12.6
Payments			(1.5)	(4.6)
Restructuring Reserve, Current	$ 3.3		3.3
Mueller One Project [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges			1.7	5.5
Project R
Restructuring Cost and Reserve [Line Items]
Inventory Write-down			$ 1.4	$ 0.0