Annual report pursuant to Section 13 and 15(d)

Concentrations of credit risk and major customers (Details)

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Concentrations of credit risk and major customers (Details)
12 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2012
Revenue Recognition      
Number of major customers 4    
Total Revenue | Foreign customers
     
Revenue Recognition      
Revenue from major customers (as a percent) 23.00% 25.00% 26.00%
Total Revenue | State government agencies
     
Revenue Recognition      
Revenue from major customers (as a percent) 55.00%    
Total Revenue | Foreign government agencies
     
Revenue Recognition      
Revenue from major customers (as a percent) 20.00%    
Total Revenue | U.S.-based federal government agencies
     
Revenue Recognition      
Revenue from major customers (as a percent) 17.00%    
Total Revenue | Other sources including local municipalities and commercial customers
     
Revenue Recognition      
Revenue from major customers (as a percent) 8.00%    
Total Revenue | State of Texas
     
Revenue Recognition      
Revenue from major customers (as a percent) 10.00% 14.00% 18.00%
Total Revenue | Australia
     
Revenue Recognition      
Revenue from major customers (as a percent) 10.00% 12.00% 16.00%
Total Revenue | U.S. Federal
     
Revenue Recognition      
Revenue from major customers (as a percent) 17.00% 12.00%  
Total Revenue | U.S. Federal | Maximum
     
Revenue Recognition      
Revenue from major customers (as a percent)     10.00%
Total Revenue | State of California
     
Revenue Recognition      
Revenue from major customers (as a percent) 10.00%   10.00%
Total Revenue | State of California | Maximum
     
Revenue Recognition      
Revenue from major customers (as a percent)   10.00%