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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Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Segment Reporting Information [Line Items]
Revenues	$ 257.7	$ 234.0	$ 470.3	$ 426.8
Operating income	35.8	22.2	56.1	38.1
Depreciation and amortization	14.3	13.4	28.3	25.5
Restructuring	0.9	6.9	3.3	10.1
Payments to Acquire Productive Assets	22.1	14.6	37.3	30.5
Total assets	1,328.2		1,328.2		$ 1,337.3
Intangible intangible assets, net	420.7		420.7		$ 433.7
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Revenues	240.3	214.1	433.1	386.1
Operating income	50.4	40.1	86.1	71.0
Depreciation and amortization	12.1	11.4	24.1	21.5
Restructuring	0.4	1.1	0.4	1.1
Payments to Acquire Productive Assets	21.2	13.0	35.7	27.8
Mueller Co. [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	59.9	55.0	106.4	95.3
Mueller Co. [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	55.1	44.9	97.0	82.8
Mueller Co. [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	44.9	41.2	84.5	75.9
Mueller Co. [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	57.7	50.6	103.7	95.3
Mueller Co. [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	15.0	15.2	26.6	25.1
Mueller Co. [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	7.7	7.2	14.9	11.7
Mueller Co. [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	217.6	191.7	391.6	349.3
Mueller Technologies [Member]
Segment Reporting Information [Line Items]
Revenues	17.4	19.9	37.2	40.7
Operating income	(4.7)	(3.6)	(6.7)	(7.3)
Depreciation and amortization	2.1	1.9	4.1	3.9
Restructuring	0.0	0.0	0.0	0.0
Payments to Acquire Productive Assets	0.7	1.6	1.3	2.7
Mueller Technologies [Member] \| Central Region [Member]
Segment Reporting Information [Line Items]
Revenues	3.6	7.4	8.3	13.9
Mueller Technologies [Member] \| Northeast Region [Member] [Member]
Segment Reporting Information [Line Items]
Revenues	4.4	3.4	10.5	6.8
Mueller Technologies [Member] \| Southeast Region [Member]
Segment Reporting Information [Line Items]
Revenues	5.3	7.0	11.1	13.8
Mueller Technologies [Member] \| Western Region [Member]
Segment Reporting Information [Line Items]
Revenues	3.0	1.5	5.0	4.2
Mueller Technologies [Member] \| CANADA
Segment Reporting Information [Line Items]
Revenues	0.3	0.1	0.9	0.3
Mueller Technologies [Member] \| Other International Locations [Member]
Segment Reporting Information [Line Items]
Revenues	0.8	0.5	1.4	1.7
Mueller Technologies [Member] \| UNITED STATES
Segment Reporting Information [Line Items]
Revenues	$ 16.3	$ 19.3	$ 34.9	$ 38.7