Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	$ 310.1	$ 301.0	$ 836.4	$ 853.1
2013	1.5	1.8	4.5	5.5
Operating income	29.7	31.5	73.9	65.2
Depreciation and amortization	13.1	14.5	39.2	43.2
Mueller Co.	21.5	11.8	23.2	20.7
Payments to Acquire Productive Assets	7.3	9.3	22.6	26.3
Total assets	1,230.9		1,230.9		$ 1,229.8
Intangible intangible assets, net	491.4		491.4		$ 507.3
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	198.7	187.8	525.6	510.2
2013	1.5	1.8	4.4	5.4
Operating income	51.7	46.7	110.4	91.5
Depreciation and amortization	8.5	9.7	25.5	29.1
Mueller Co.	2.4	0.1	3.0	8.2
Payments to Acquire Productive Assets	3.6	4.8	12.4	13.1
Anvil [Member]
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	85.4	89.2	251.4	277.4
2013	0.0	0.0	0.1	0.1
Operating income	6.5	7.0	18.1	21.4
Depreciation and amortization	3.3	3.6	9.9	10.8
Mueller Co.	0.9	0.2	1.5	0.4
Payments to Acquire Productive Assets	2.3	2.5	5.6	8.5
Mueller Technologies [Member]
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	26.0	24.0	59.4	65.5
2013	0.0	0.0	0.0	0.0
Operating income	(1.5)	(3.5)	(10.2)	(11.1)
Depreciation and amortization	1.2	1.1	3.5	3.0
Mueller Co.	0.0	0.0	0.5	0.1
Payments to Acquire Productive Assets	1.4	1.9	4.5	4.6
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(27.0)	(18.7)	(44.4)	(36.6)
Depreciation and amortization	0.1	0.1	0.3	0.3
Mueller Co.	18.2	11.5	18.2	12.0
Payments to Acquire Productive Assets	$ 0.0	$ 0.1	$ 0.1	$ 0.1