Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Narrative (Details)

v3.21.1
Stockholders' Equity - Narrative (Details) - USD ($)
 3 Months Ended 6 Months Ended 12 Months Ended
Nov. 10, 2020
Oct. 11, 2019
Feb. 11, 2019
Oct. 25, 2018
Sep. 07, 2018
Sep. 05, 2018
Dec. 31, 2016
Mar. 31, 2021
Mar. 31, 2020
Mar. 31, 2021
Mar. 31, 2020
Sep. 30, 2020
Oct. 10, 2019
Feb. 27, 2015
Class Of Stock [Line Items]                            
Number of shares authorized to be repurchased (up to)                         7,000  
Stock compensation expense               $ 222,000 $ 162,000 $ 444,000 $ 355,000      
Restricted Stock                            
Class Of Stock [Line Items]                            
Stock compensation expense               40,000 26,000 65,000 52,000      
Unrecognized expense               119,000   119,000   $ 0    
Weighted average fair value (in dollars per share) $ 31.20                          
Options                            
Class Of Stock [Line Items]                            
Stock compensation expense               61,000 $ 301,000 121,000 $ 383,000      
Unrecognized expense               $ 255,000   $ 255,000   $ 376,000    
Unrecognized compensation cost, expected recognition period                   1 year 2 months 19 days        
2015 Option Grants                            
Class Of Stock [Line Items]                            
Number of shares authorized to be repurchased (up to)                           1,250,000
2015 Option Grants | Restricted Stock                            
Class Of Stock [Line Items]                            
Number of restricted shares awarded 5,885                          
2015 Option Grants | Minimum                            
Class Of Stock [Line Items]                            
Award vesting period                   1 year        
2015 Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Award vesting period                   6 years        
2020 Option Grants                            
Class Of Stock [Line Items]                            
Granted (in shares)   118,000                        
Shares issued (in dollars per share)   $ 33.96                        
Percentage of options                   25.00%        
Period following an executive's termination of employment for a number of reasons   18 months                        
Period following an executive's termination of employment without cause   12 months                        
2020 Option Grants | Tranche One                            
Class Of Stock [Line Items]                            
Percentage of options   25.00%                        
Period of consecutive trading days   20 days                        
Amount per share (in dollars per share)   $ 35.00                        
2020 Option Grants | Tranche Two                            
Class Of Stock [Line Items]                            
Percentage of options   25.00%                        
Period of consecutive trading days   20 days                        
Amount per share (in dollars per share)   $ 40.00                        
2020 Option Grants | Tranche Three                            
Class Of Stock [Line Items]                            
Percentage of options   25.00%                        
Period of consecutive trading days   20 days                        
Amount per share (in dollars per share)   $ 45.00                        
2020 Option Grants | Tranche Four                            
Class Of Stock [Line Items]                            
Percentage of options   25.00%                        
Period of consecutive trading days   20 days                        
Amount per share (in dollars per share)   $ 50.00                        
2020 Option Grants | Minimum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)               $ 35.00   $ 35.00        
2020 Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)               40.00   $ 40.00        
2019 Option Grants                            
Class Of Stock [Line Items]                            
Shares issued (in dollars per share)       $ 33.34                    
Period following an executive's termination of employment for a number of reasons       18 months                    
Period following an executive's termination of employment without cause       12 months                    
Number of awards vesting (in shares)                   0        
2019 Option Grants | Chief Financial Officer                            
Class Of Stock [Line Items]                            
Granted (in shares)       10,000                    
2019 Option Grants | Tranche One                            
Class Of Stock [Line Items]                            
Period of consecutive trading days       20 days                    
Amount per share (in dollars per share)       $ 40.00                    
Number of awards vesting (in shares)       3,333                    
2019 Option Grants | Tranche Two                            
Class Of Stock [Line Items]                            
Period of consecutive trading days       20 days                    
Amount per share (in dollars per share)       $ 45.00                    
Number of awards vesting (in shares)       3,333                    
2019 Option Grants | Tranche Three                            
Class Of Stock [Line Items]                            
Period of consecutive trading days       20 days                    
Amount per share (in dollars per share)       $ 50.00                    
Number of awards vesting (in shares)       3,334                    
2019 Option Grants | Options                            
Class Of Stock [Line Items]                            
Grants in period, weighted average (in dollars per share)                   $ 7.10        
2019 Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)               40.00   $ 40.00        
2018 Option Grants                            
Class Of Stock [Line Items]                            
Shares issued (in dollars per share)         $ 33.60                  
Percentage of options                   0.00%   25.00%    
Period following an executive's termination of employment for a number of reasons         18 months                  
Period following an executive's termination of employment without cause         12 months                  
2018 Option Grants | Chief Financial Officer                            
Class Of Stock [Line Items]                            
Granted (in shares)         90,000                  
2018 Option Grants | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Granted (in shares)         210,000                  
2018 Option Grants | Tranche One                            
Class Of Stock [Line Items]                            
Percentage of options         25.00%                  
Period of consecutive trading days         20 days                  
Amount per share (in dollars per share)         $ 35.00                  
2018 Option Grants | Tranche One | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Period of consecutive trading days     20 days                      
Amount per share (in dollars per share)     $ 35.00                      
Number of shares expected to vest (in shares)     26,250                      
2018 Option Grants | Tranche Two                            
Class Of Stock [Line Items]                            
Percentage of options         25.00%                  
Period of consecutive trading days         20 days                  
Amount per share (in dollars per share)         $ 40.00                  
2018 Option Grants | Tranche Two | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Period of consecutive trading days     20 days                      
Amount per share (in dollars per share)     $ 40.00                      
Number of shares expected to vest (in shares)     26,250                      
2018 Option Grants | Tranche Three                            
Class Of Stock [Line Items]                            
Percentage of options         25.00%                  
Period of consecutive trading days         20 days                  
Amount per share (in dollars per share)         $ 45.00                  
2018 Option Grants | Tranche Four                            
Class Of Stock [Line Items]                            
Percentage of options         25.00%                  
Period of consecutive trading days         20 days                  
Amount per share (in dollars per share)         $ 50.00                  
2018 Option Grants | Minimum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)                       $ 35.00    
2018 Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)               40.00   $ 40.00        
2016 Option Grants                            
Class Of Stock [Line Items]                            
Shares issued (in dollars per share)             $ 27.15              
Period following an executive's termination of employment for a number of reasons             18 months              
Number of awards vesting (in shares)                   0        
2016 Option Grants | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Granted (in shares)             300,000              
2016 Option Grants | Board of Directors Chairman                            
Class Of Stock [Line Items]                            
Granted (in shares)             225,000              
Shares forfeited (in shares)           187,500                
2016 Option Grants | Tranche One                            
Class Of Stock [Line Items]                            
Percentage of options             25.00%              
Period of consecutive trading days             20 days              
Amount per share (in dollars per share)             $ 60.00              
2016 Option Grants | Tranche Two                            
Class Of Stock [Line Items]                            
Percentage of options             25.00%              
Period of consecutive trading days             20 days              
Amount per share (in dollars per share)             $ 75.00              
2016 Option Grants | Tranche Three                            
Class Of Stock [Line Items]                            
Percentage of options             25.00%              
Period of consecutive trading days             20 days              
Amount per share (in dollars per share)             $ 90.00              
2016 Option Grants | Tranche Four                            
Class Of Stock [Line Items]                            
Percentage of options             25.00%              
Period of consecutive trading days             20 days              
Amount per share (in dollars per share)             $ 105.00              
2016 Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)               60.00   $ 60.00        
2019 Modified Option Grants | Tranche One | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Number of shares expected to vest (in shares)     26,250                      
2019 Modified Option Grants | Tranche Two | Chief Executive Officer                            
Class Of Stock [Line Items]                            
Number of shares expected to vest (in shares)     26,250                      
2019 Modified Option Grants | Options                            
Class Of Stock [Line Items]                            
Grants in period, weighted average (in dollars per share)                   1.40        
2019 Modified Option Grants | Maximum                            
Class Of Stock [Line Items]                            
Share price (in dollars per share)     $ 40.00         $ 35.00   35.00        
2020 Option Grants | Options                            
Class Of Stock [Line Items]                            
Grants in period, weighted average (in dollars per share)                   $ 3.20