Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Stock-Based Compensation (Details)

v3.8.0.1
Summary of Significant Accounting Policies - Stock-Based Compensation (Details) - $ / shares
 3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2015
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee stock options granted (in shares)   0 750,000 0  
Shares issued (in dollars per share) $ 27.15        
Period of consecutive trading days 20 days        
Period following an executive's termination of employment for a number of reasons 18 months        
Restricted Shares          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Restricted shares of common stock awarded (in shares)     0 0 12,500
Weighted average fair value (in dollars per share)     $ 0.00 $ 0.00 $ 49.49
Employee Stock Option          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee stock options granted (in shares)     750,000    
Weighted average grant date fair value of option grant (in dollars per share)     $ 3.53    
Chief Executive Officer          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee stock options granted (in shares) 300,000        
Board of Directors Chairman          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Employee stock options granted (in shares) 225,000        
Tranche One          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Percentage of option price to vest 25.00%        
Amount per share (in dollars per share) $ 60.00        
Tranche Two          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Percentage of option price to vest 25.00%        
Amount per share (in dollars per share) $ 75.00        
Tranche Three          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Percentage of option price to vest 25.00%        
Amount per share (in dollars per share) $ 90.00        
Tranche Four          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Percentage of option price to vest 25.00%        
Amount per share (in dollars per share) $ 105.00