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Organization (Details) $ in Millions		3 Months Ended				6 Months Ended	9 Months Ended		12 Months Ended
	Jul. 31, 2014	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Sep. 30, 2019	Sep. 30, 2017
Segment Reporting Information [Line Items]
Beginning balance			$ 3.3				$ 3.3
Restructuring		$ 2.6		$ 1.2			8.4	$ 5.0
Payments			$ 6.3
Number of Reportable Segments			2
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	49.00%
Payments for (Proceeds from) Other Investing Activities						$ 26.6
Defined Benefit Plan, Net Periodic Benefit Cost other than Service Cost		0.2		0.4			0.7	1.1
Revenue, Net		$ 250.2		$ 232.2			$ 661.7	$ 599.1
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		24.50%		35.00%			24.50%	35.00%		35.00%
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Restructuring		$ 0.0		$ 0.4			$ 0.1	$ 2.1
Revenue, Net		$ 224.1		$ 207.6			$ 595.3	$ 535.5
General and Administrative Expense [Member] | Mueller Co. [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost other than Service Cost					$ 0.3	0.8
Cost of Sales [Member] | Mueller Co. [Member]
Segment Reporting Information [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost other than Service Cost					$ 0.1	$ 0.3
Scenario, Forecast [Member]
Segment Reporting Information [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent									21.00%

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