Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Narrative (Details)

v3.20.4
Stockholders' Equity - Narrative (Details) - USD ($)
 3 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
Dec. 31, 2020
Dec. 31, 2019
Sep. 30, 2020
Dec. 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 $ 193,000        
Restricted Stock                          
Class Of Stock [Line Items]                          
Stock compensation expense               25,000 26,000        
Unrecognized expense               159,000   $ 0      
Weighted average fair value (in dollars per share) $ 31.20                        
Options                          
Class Of Stock [Line Items]                          
Stock compensation expense               $ 60,000 $ 82,000        
Unrecognized expense                   $ 376,000 $ 316,000    
Unrecognized compensation cost, expected recognition period               1 year 5 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      
2020 Option Grants | Maximum                          
Class Of Stock [Line Items]                          
Share price (in dollars per share)               $ 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          
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          
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          
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          
2020 Option Grants | Options                          
Class Of Stock [Line Items]                          
Grants in period, weighted average (in dollars per share)               $ 3.20