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Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Jan. 06, 2017	Sep. 30, 2014
Gain (Loss) on Discontinuation of Interest Rate Cash Flow Hedge Due to Forecasted Transaction Probable of Not Occurring, Net	$ 0.0	$ 2.4	$ 0.0
Product Warranty Expense	3.9	18.7	12.3
Asset Retirement Obligation	4.5	4.1
Exposure to Workers Compensation Claims, Per Incident	1.0
Discontinued Operations, Receivable from Buyer of Discontinued Operation				$ 1.9	$ 11.8
Workers Compensation Undiscounted Basis Liability	8.7	9.1
Workers' Compensation Liability	$ 7.6	$ 7.7
Income Tax Benefit, Likelihood of Realization Threshold	50.00%
Debt Issuance Costs, Net	$ 6.3
Minimum [Member]
Finite-Lived Tangible Asset, Useful Life, Maximum		3 years
Maximum [Member]
Finite-Lived Tangible Asset, Useful Life, Maximum		10 years
Land Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Land Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	20 years
Building [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	10 years
Building [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	40 years
Machinery and Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life, Minimum	3 years
Machinery and Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	15 years
Software and Software Development Costs [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life, Minimum	6 years
U.S. Pipe [Member] | Maximum [Member]
Discontinued Operations, Receivable from Buyer of Discontinued Operation	$ 3.4
Other Current Assets [Member] | U.S. Pipe [Member]
Discontinued Operations, Receivable from Buyer of Discontinued Operation	0.4
Other Noncurrent Assets [Member] | U.S. Pipe [Member]
Discontinued Operations, Receivable from Buyer of Discontinued Operation	3.0
Revolving Credit Facility [Member]
Debt Issuance Costs, Net	0.5
Secured Debt [Member]
Debt Issuance Costs, Net	5.8	$ 6.6
Unsecured Debt [Member]
Debt Issuance Costs, Net	$ 5.8
Product Concentration Risk [Member]
Product Warranty Expense		$ 14.1	$ 9.8

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