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Commitments and Contingencies (Details) CAD in Millions, $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($) | Sep. 30, 2017 USD ($) | Sep. 30, 2017 CAD | Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($)
Loss Contingency, Damages Sought, Value | CAD |  |  |  |  | CAD 10.0 |  |
Document Period End Date |  |  |  | Sep. 30, 2017 | Sep. 30, 2017 |  |
Walter Energy tax assessment |  |  |  | $ 33.0 |  |  |
Amount receivable pending completion of an IRS audit |  |  |  | 11.6 |  |  |
Product Warranty Expense |  |  |  | 12.3 |  | $ 5.3 | $ 5.1
Operating Leases |  |  |  |  |  |  |
Rent expense |  | $ 5.8 | $ 5.8 | 5.9 |  |  |
Future minimum payment under non-cancelable operating leases, CY Plus 1 |  |  |  | 3.6 |  |  |
Future minimum payment under non-cancelable operating leases, CY Plus 2 |  |  |  | 2.5 |  |  |
Future minimum payment under non-cancelable operating leases, CY Plus 3 |  |  |  | 2.3 |  |  |
Future minimum payment under non-cancelable operating leases, CY Plus 4 |  |  |  | 2.2 |  |  |
Future minimum payment under non-cancelable operating leases, CY Plus 5 |  |  |  | 1.9 |  |  |
Future minimum payment under non-cancelable operating leases, CY plus 6 and up |  |  |  | 4.5 |  |  |
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 |  |  |  | $ 9.8 |  |  |

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