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Equity (Employee Stock Purchase Plan) (Details) - USD ($)
12 Months Ended
Sep. 30, 2019
Sep. 30, 2018
Sep. 30, 2017
Jul. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Aggregate common shares issued under ESPP (in shares) 2,971,843      
Purchases under the employee stock purchase plan (in shares) 543,731      
Employee stock purchase plan        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
ESPP offering period (months) 6 months      
Purchase price (as percentage of market price) 85.00%      
Annual contribution (as percentage of compensation) 10.00%      
Annual contribution $ 25,000      
Total number of shares available under ESPP       3,515,574
Common Stock        
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]        
Issuance of common stock - ESPP (in shares) 197,000 171,000 133,000