Segment Information (Schedule Of Selected Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Sep. 30, 2014
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	$ 301.0	$ 318.5	$ 853.1	$ 864.0
2013	1.8	1.6	5.5	4.9
Operating income	31.5	41.8	65.2	81.1
Depreciation and amortization	14.5	14.0	43.2	42.5
Restructuring	0.2	0.2	9.1	3.0
Payments to Acquire Productive Assets	9.3	7.2	26.3	25.5
Total assets	1,197.4		1,197.4		$ 1,317.1
Intangible intangible assets, net	514.1		514.1		$ 533.6
Mueller Co. [Member]
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	211.8	214.0	575.7	570.3
2013	1.8	1.6	5.4	4.8
Operating income	43.2	42.2	80.4	84.3
Depreciation and amortization	10.8	10.4	32.1	31.6
Restructuring	0.1	0.2	8.3	1.9
Payments to Acquire Productive Assets	6.7	5.0	17.7	15.9
Anvil [Member]
Segment Reporting Information [Line Items]
Net sales, excluding intercompany	89.2	104.5	277.4	293.7
2013	0.0	0.0	0.1	0.1
Operating income	7.0	9.5	21.4	24.3
Depreciation and amortization	3.6	3.5	10.8	10.6
Restructuring	0.2	0.0	0.4	1.1
Payments to Acquire Productive Assets	2.5	2.2	8.5	9.4
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(18.7)	(9.9)	(36.6)	(27.5)
Depreciation and amortization	0.1	0.1	0.3	0.3
Restructuring	(0.1)	0.0	0.4	0.0
Payments to Acquire Productive Assets	$ 0.1	$ 0.0	$ 0.1	$ 0.2