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Summary of Significant Accounting Policies (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Sep. 30, 2014
segment
item
Sep. 30, 2013
Sep. 30, 2012
Summary of Significant Accounting Policies      
Number of business segments 3    
Percentage of revenue from services 10.00% 12.00% 13.00%
Asset retirement obligations $ 0 $ 0  
Number of reclamation obligations 1    
Advertising costs 8.0 6.2 5.9
Warranty costs $ 1.8 $ 1.5 $ 1.2
Estimated forfeiture rate for unvested awards 1.00%    
Convertible Senior Subordinated Notes 2.50 Percent Due 2014
     
Summary of Significant Accounting Policies      
Interest rate on long-term debt (as a percent) 2.50% 2.50%  
Minimum
     
Summary of Significant Accounting Policies      
Economic interest 20.00%    
Estimated forfeiture rates 1.00%    
Minimum | Customer Concentration Risk
     
Summary of Significant Accounting Policies      
Revenue accounted for, percentage 10.00%    
Maximum
     
Summary of Significant Accounting Policies      
Economic interest 50.00%    
Ownership percentage - cost method 20.00%    
Estimated forfeiture rates 3.00%    
Maximum | Geographic Concentration Risk
     
Summary of Significant Accounting Policies      
Revenue accounted for, percentage 10.00%