Annual report pursuant to Section 13 and 15(d)

Business and summary of significant accounting policies - Cash, Goodwill and Long-lived Assets (Details)

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Business and summary of significant accounting policies - Cash, Goodwill and Long-lived Assets (Details) - USD ($)
12 Months Ended
Jul. 01, 2017
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Property and Equipment        
Goodwill, impairment loss $ 0 $ 0    
Restricted cash   13,500,000 $ 14,100,000  
Impairment of long-lived assets held-for-use   $ 0 $ 0 $ 0
Buildings | Maximum        
Property and Equipment        
Estimated useful lives   39 years    
Office furniture and equipment. | Maximum        
Property and Equipment        
Estimated useful lives   7 years    
Software development costs. | Minimum        
Property and Equipment        
Estimated useful lives   3 years    
Software development costs. | Maximum        
Property and Equipment        
Estimated useful lives   8 years