Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 212.6	$ 192.8
Operating income	20.3	15.9
Depreciation and amortization	14.0	12.1
Restructuring	2.4	3.2
Payments to Acquire Productive Assets	15.2	15.9
Total assets	1,309.0		$ 1,337.3
Intangible intangible assets, net	428.0		$ 433.7
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Revenues	192.8	172.0
Operating income	35.7	30.9
Depreciation and amortization	12.0	10.1
Restructuring	0.0	0.0
Payments to Acquire Productive Assets	14.5	14.8
Mueller Co. [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	46.5	40.3
Mueller Co. [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	41.9	37.9
Mueller Co. [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	39.6	34.7
Mueller Co. [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	46.0	44.8
Mueller Co. [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	11.6	9.9
Mueller Co. [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	7.2	4.4
Mueller Co. [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	174.0	157.7
Mueller Technologies [Member]
Segment Reporting Information [Line Items]
Revenues	19.8	20.8
Operating income	(2.0)	(3.7)
Depreciation and amortization	2.0	2.0
Restructuring	0.0	0.0
Payments to Acquire Productive Assets	0.6	1.1
Mueller Technologies [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	4.7	6.5
Mueller Technologies [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	6.1	3.4
Mueller Technologies [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	5.8	6.8
Mueller Technologies [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	2.0	2.7
Mueller Technologies [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	0.6	0.2
Mueller Technologies [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	0.6	1.2
Mueller Technologies [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	18.6	19.4
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(13.4)	(11.3)
Depreciation and amortization	0.0	0.0
Restructuring	2.4	3.2
Payments to Acquire Productive Assets	$ 0.1	$ 0.0

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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