Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 192.8	$ 178.3
Operating income	15.9	20.7
Depreciation and amortization	12.1	10.6
Restructuring	3.2	3.9
Payments to Acquire Productive Assets	15.9	6.4
Total assets	1,259.1		$ 1,291.9
Intangible intangible assets, net	412.6		$ 408.1
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Revenues	172.0	160.1
Operating income	30.9	28.1
Depreciation and amortization	10.1	9.1
Restructuring	0.0	0.0
Payments to Acquire Productive Assets	14.8	4.8
Mueller Co. [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	40.3	39.4
Mueller Co. [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	37.9	37.7
Mueller Co. [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	34.7	28.9
Mueller Co. [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	44.8	39.9
Mueller Co. [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	157.7	145.9
Mueller Co. [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	9.9	11.0
Mueller Co. [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	4.4	3.2
Mueller Technologies [Member]
Segment Reporting Information [Line Items]
Revenues	20.8	18.2
Operating income	(3.7)	(4.7)
Depreciation and amortization	2.0	1.4
Restructuring	0.0	0.1
Payments to Acquire Productive Assets	1.1	1.5
Mueller Technologies [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	6.5	3.5
Mueller Technologies [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	3.4	4.0
Mueller Technologies [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	6.8	7.5
Mueller Technologies [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	2.7	1.9
Mueller Technologies [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	19.4	16.9
Mueller Technologies [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	0.2	0.1
Mueller Technologies [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	1.2	1.2
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(11.3)	(2.7)
Depreciation and amortization	0.0	0.1
Restructuring	3.2	3.8
Payments to Acquire Productive Assets	$ 0.0	$ 0.1

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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