Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation and Other Compensation Matters (Details 7)

v3.10.0.1
Share-Based Compensation and Other Compensation Matters (Details 7)
$ / shares in Units, $ in Thousands
12 Months Ended
Feb. 22, 2018
shares
Jan. 01, 2018
$ / shares
Feb. 07, 2017
shares
Jan. 01, 2017
$ / shares
Oct. 30, 2016
shares
Jul. 12, 2016
shares
May 30, 2016
shares
Dec. 31, 2018
USD ($)
Percentile_Rank
$ / shares
Dec. 31, 2017
USD ($)
$ / shares
Dec. 31, 2016
USD ($)
$ / shares
May 31, 2017
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Decrease in tax benefit from share-based compensation                 $ 13 $ 331  
Executive transition costs                   6,500  
Stock Options [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Expiration period               10 years      
Performance share units [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Estimated pre-vesting forfeitures               0.00%      
Unrecognized compensation cost               $ 1,700      
Expected weighted average period during which unrecognized compensation cost will be recognized               2 years      
Performance period of the award               3 years      
Grant date fair value                 236    
Deferred Share Awards [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Estimated pre-vesting forfeitures               0.00%      
Unrecognized compensation cost               $ 137      
Aggregate intrinsic value               $ 154 $ 508 $ 322  
Grant date fair value (in dollars per share) | $ / shares               $ 28.08 $ 32.47 $ 26.89  
Restricted shares [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Unrecognized compensation cost               $ 7,900      
Expected weighted average period during which unrecognized compensation cost will be recognized               2 years      
Aggregate intrinsic value               $ 4,600 $ 5,300 $ 5,400  
Grant date fair value (in dollars per share) | $ / shares               $ 25.62 $ 33.84 $ 24.77  
Restricted shares [Member] | Minimum [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Estimated pre-vesting forfeitures               0.00%      
Restricted shares [Member] | Maximum [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Estimated pre-vesting forfeitures               6.00%      
Options [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Aggregate intrinsic value of options exercised                 $ 18    
2017 Omnibus Equity and Incentive Plan [Member] | Maximum [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Number of common shares of beneficial interest authorized to be issued | shares                     3,400,000.0
2018 PSU Grants [Member] | Performance share units [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
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      
Grant date fair value (in dollars per share) | $ / shares   $ 31.97                  
2014 and 2015 Performance Share Unit Grants [Member] | Performance share units [Member] | Executive Officer [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Shares issued for PSU Awards Vested in Period (in shares) | shares           20,569 10,326        
2014, 2015 and 2016 Performance Share Unit Grants [Member] | Performance share units [Member] | Executive Officer [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Shares issued for PSU Awards Vested in Period (in shares) | shares         2,248            
2017 PSU Grants [Member] | Performance share units [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Grant date fair value (in dollars per share) | $ / shares       $ 38.43              
2014 PSU Grants [Member] | Performance share units [Member] | Chief Executive Officer [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Shares issued for PSU Awards Vested in Period (in shares) | shares     9,763                
2015 PSU Grants [Member] | Performance share units [Member] | Executive Officer [Member]                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Shares issued for PSU Awards Vested in Period (in shares) | shares 13,328