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Commitments and Contingencies (Details) $ in Millions, $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 CAD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)
Loss Contingency, Damages Sought, Value					$ 10.0
Document Period End Date				Sep. 30, 2018	Sep. 30, 2018
Walter Energy tax assessment						$ 33.0
Product Warranty Expense				$ 18.7		12.3	$ 5.3
Operating Leases
Rent expense	$ 5.8		$ 5.8	6.4
Future minimum payment under non-cancelable operating leases, CY Plus 1				4.3
Future minimum payment under non-cancelable operating leases, CY Plus 2				3.9
Future minimum payment under non-cancelable operating leases, CY Plus 3				3.5
Future minimum payment under non-cancelable operating leases, CY Plus 4				3.0
Future minimum payment under non-cancelable operating leases, CY Plus 5				2.0
Future minimum payment under non-cancelable operating leases, CY plus 6 and up				3.2
IRS-Walter Energy Claim 1 Total [Member]
Loss Contingency, Damages Sought, Value		$ 554.3
IRS-Walter Energy Claim 1 Priority [Member]
Loss Contingency, Damages Sought, Value		229.1
IRS-Walter Energy Claim 2 [Member]
Loss Contingency, Damages Sought, Value		860.4
IRS-Walter Energy Claim 2 Priority [Member]
Loss Contingency, Damages Sought, Value		$ 535.3
Product Concentration Risk [Member]
Product Warranty Expense				$ 14.1		$ 9.8

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