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Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Sep. 30, 2015 | Jan. 06, 2017 | Sep. 30, 2014
Product Warranty Expense | $ 12.3 | $ 5.3 | $ 5.1 |  |
Asset Retirement Obligation | 3.8 | 7.5 |  |  |
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 | 10.7 | 13.7 |  |  |
Workers' Compensation Liability | $ 9.1 | 11.8 |  |  |
Income Tax Benefit, Likelihood of Realization Threshold | 50.00% |  |  |  |
Debt Issuance Costs, Net | $ 7.4 |  |  |  |
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 | $ 4.1 |  |  |  |
Other Current Assets [Member] | U.S. Pipe [Member] |  |  |  |  |
Discontinued Operations, Receivable from Buyer of Discontinued Operation | 0.5 |  |  |  |
Other Noncurrent Assets [Member] | U.S. Pipe [Member] |  |  |  |  |
Discontinued Operations, Receivable from Buyer of Discontinued Operation | 3.6 |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |
Debt Issuance Costs, Net | 1.5 |  |  |  |
Secured Debt [Member] |  |  |  |  |
Debt Issuance Costs, Net | 5.9 | $ 6.3 |  |  |
Product Concentration Risk [Member] |  |  |  |  |
Product Warranty Expense | $ 9.8 |  |  |  |

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