Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Sep. 30, 2018
Segment Reporting Information [Line Items]
Revenues	$ 274.3	$ 250.2	$ 701.1	$ 661.7
Operating income	47.2	30.6	85.3	81.2
Depreciation and amortization	13.3	10.8	38.8	32.3
Restructuring	2.5	2.6	12.6	8.4
Payments to Acquire Productive Assets	22.4	12.5	52.9	26.9
Total assets	1,293.3		1,293.3		$ 1,291.9
Intangible intangible assets, net	439.2		439.2		$ 408.1
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Revenues	250.2	224.1	636.3	595.3
Operating income	60.6	57.0	131.6	130.0
Depreciation and amortization	11.3	9.2	32.8	27.7
Restructuring	0.0	0.0	1.1	0.1
Payments to Acquire Productive Assets	18.9	10.7	46.7	21.8
Mueller Co. [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	58.8	55.8	154.1	149.3
Mueller Co. [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	52.0	39.1	134.8	105.6
Mueller Co. [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	41.3	45.0	117.2	127.7
Mueller Co. [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	63.8	54.5	159.1	148.7
Mueller Co. [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	215.9	194.4	565.2	531.3
Mueller Co. [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	24.1	25.2	49.3	53.1
Mueller Co. [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	10.2	4.5	21.8	10.9
Mueller Technologies [Member]
Segment Reporting Information [Line Items]
Revenues	24.1	26.1	64.8	66.4
Operating income	(2.2)	(16.1)	(9.5)	(24.7)
Depreciation and amortization	2.0	1.5	5.9	4.4
Restructuring	0.0	0.0	0.0	0.1
Payments to Acquire Productive Assets	1.8	2.0	4.5	5.0
Mueller Technologies [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	6.6	3.9	20.5	11.4
Mueller Technologies [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	5.5	4.5	12.3	13.8
Mueller Technologies [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	8.0	13.2	21.7	28.8
Mueller Technologies [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	2.3	3.2	6.6	8.6
Mueller Technologies [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	22.4	24.8	61.1	62.6
Mueller Technologies [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	0.5	0.8	0.8	1.3
Mueller Technologies [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	1.2	0.5	2.9	2.5
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(11.2)	(10.3)	(36.8)	(24.1)
Depreciation and amortization	0.0	0.1	0.1	0.2
Restructuring	2.5	2.6	11.5	8.2
Payments to Acquire Productive Assets	$ 1.7	$ (0.2)	$ 1.7	$ 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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