Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation and Other Compensation Matters (Narrative) (Details)

v3.20.4
Share-Based Compensation and Other Compensation Matters (Narrative) (Details)
$ / shares in Units, $ in Thousands
12 Months Ended
Feb. 03, 2021
shares
Jan. 13, 2020
shares
Jan. 18, 2019
shares
Jan. 01, 2018
$ / shares
Dec. 31, 2020
USD ($)
rank
form
Percentile_Rank
$ / shares
Dec. 31, 2019
USD ($)
$ / shares
Dec. 31, 2018
USD ($)
$ / shares
May 31, 2017
shares
Performance Shares, Profit Interest Units and Deferred Share Awards                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Estimated pre-vesting forfeitures         0.00% 0.00% 0.00%  
Restricted shares                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unrecognized compensation cost         $ 5,600      
Expected weighted average period during which unrecognized compensation cost will be recognized         2 years      
Aggregate intrinsic value of shares that vested         $ 4,400 $ 4,900 $ 4,600  
Grant date fair value (in dollars per share) | $ / shares         $ 25.22 $ 26.56 $ 25.62  
Restricted shares | Minimum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Estimated pre-vesting forfeitures         0.00% 0.00% 0.00%  
Restricted shares | Maximum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Estimated pre-vesting forfeitures         8.00% 8.00% 8.00%  
Performance-based PIUs                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unrecognized compensation cost         $ 2,200      
Expected weighted average period during which unrecognized compensation cost will be recognized         2 years      
Vesting period         3 years      
Percentile ranks to fall between for PIUs | rank         2      
Percent of award distribution rights         10.00%      
Performance period of the award         3 years      
The number of percentile ranks to fall between to earn interpolated PSUs between such percentile ranks, conditioned on the percentile rank exceeding 25% | Percentile_Rank         2      
Time-based PIUs                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unrecognized compensation cost         $ 2,100      
Expected weighted average period during which unrecognized compensation cost will be recognized         3 years      
Aggregate intrinsic value of shares that vested         $ 640      
Grant date fair value (in dollars per share) | $ / shares         $ 25.47 $ 26.01    
Deferred Share Awards                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Unrecognized compensation cost         $ 121      
Aggregate intrinsic value of shares that vested           $ 86 $ 154  
Grant date fair value (in dollars per share) | $ / shares         $ 23.68 $ 27.60 $ 28.08  
Profit Interest Units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of forms of profit interest units available to executives and trustees | form         2      
Performance share units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Performance period of the award         3 years      
2017 Omnibus Equity and Incentive Plan | Maximum                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Number of common shares of beneficial interest authorized to be issued | shares               3,400,000
2016 PSU Grants | Performance share units | Executives                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares issued for PSU awards vested in period (in shares) | shares     44,757          
2017 PSU Grants | Performance share units | Executives                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares issued for PSU awards vested in period (in shares) | shares   23,181            
2018 PSU Grants | Performance share units                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Grant date fair value (in dollars per share) | $ / shares       $ 31.97        
Baseline Common Share Value (in dollars per share) | $ / shares       $ 29.20        
Expected volatility of common shares (as a percent)       17.00%        
Risk-free interest rate (as a percent)       2.04%        
2018 PSU Grants | Performance share units | Executives | Subsequent Event [Member]                
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                
Shares issued for PSU awards vested in period (in shares) | shares 93,824