Annual report pursuant to Section 13 and 15(d)

Common Stock and Options - Narrative (Details)

v3.8.0.1
Common Stock and Options - Narrative (Details)
 3 Months Ended 12 Months Ended
Dec. 31, 2016
$ / shares
shares
Sep. 30, 2015
shares
Sep. 30, 2017
USD ($)
$ / shares
shares
Sep. 30, 2016
USD ($)
$ / shares
shares
Sep. 30, 2015
executive
$ / shares
shares
May 31, 2017
shares
Mar. 31, 2017
shares
Jan. 27, 2017
shares
Feb. 27, 2015
$ / shares
Sep. 30, 2013
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares authorized to be repurchased (up to) (in shares) | shares   170,000 7,000,000   170,000 2,000,000 5,000,000     105,000
Employee stock options granted (in shares) | shares   0 750,000 0            
Shares issued (in dollars per share) | $ / shares $ 27.15                  
Period of consecutive trading days 20 days                  
Period following an executive's termination of employment for a number of reasons 18 months                  
Share price (in dollars per share) | $ / shares     $ 34.15           $ 45.67  
Restricted Shares                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Restricted shares of common stock awarded (in shares) | shares     0 0 12,500          
Weighted average fair value (in dollars per share) | $ / shares     $ 0.00 $ 0.00 $ 49.49          
Total stock compensation expense | $     $ 264,000 $ 150,000            
Unrecognized compensation costs | $     149,000 413,000            
Employee Stock Option                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Total stock compensation expense | $     616,000 $ 0            
Unrecognized compensation costs | $     $ 2,030,000              
Employee stock options granted (in shares) | shares     750,000              
Weighted average grant date fair value of option grant (in dollars per share) | $ / shares     $ 3.53              
Number of shares available for issuance (in shares) | shares     750,000 0            
The 2015 Plan                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares authorized to be repurchased (up to) (in shares) | shares               1,250,000    
The 2015 Plan | Restricted Shares                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Restricted shares of common stock awarded (in shares) | shares         12,500          
Number of senior executives | executive         2          
Weighted average fair value (in dollars per share) | $ / shares         $ 49.49          
The 2015 Plan | Employee Stock Option                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Number of shares available for issuance (in shares) | shares     487,500              
Minimum | The 2015 Plan                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Vesting period         1 year          
Minimum | The 2015 Plan | Restricted Shares                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Vesting period         3 years          
Maximum                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Share price (in dollars per share) | $ / shares     $ 34.45              
Maximum | The 2015 Plan                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Vesting period         6 years          
Maximum | The 2015 Plan | Restricted Shares                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Vesting period         5 years          
Chief Executive Officer                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Employee stock options granted (in shares) | shares 300,000                  
Board of Directors Chairman                    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                    
Employee stock options granted (in shares) | 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) | $ / shares $ 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) | $ / shares $ 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) | $ / shares $ 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) | $ / shares $ 105.00