XML 98 R77.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock-based Compensation - (Details) - USD ($)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 12 Months Ended
Aug. 07, 2014
Mar. 31, 2017
Mar. 31, 2016
Mar. 31, 2015
Dec. 31, 2017
Mar. 31, 2015
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Jul. 24, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Non-cash share compensation             $ 6,695 $ 5,672 $ 3,798    
2013 Plan | Restricted common shares                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Number of shares authorized 2,450,000                   600,000
Number of additional shares authorized 1,850,000                    
Granted (in shares)             143,593 155,306 162,522    
Share-based compensation, gross             $ 2,800 $ 2,800 $ 2,600    
Non-cash share compensation           $ 2,900 3,100 3,600      
Unrecognized compensation expense         $ 1,000   $ 1,000 $ 1,200   $ 2,100  
Grant date value (in dollars per share)             $ 19.74 $ 17.96 $ 15.95    
2013 Plan | Restricted common shares | Minimum                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Vesting period             1 year 1 year 1 year    
2013 Plan | Restricted common shares | Maximum                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Vesting period             3 years 3 years 3 years    
2013 Plan | Restricted Share Units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Granted (in shares)       75,250              
Non-cash share compensation           $ 900 $ 3,600 $ 2,100      
Unrecognized compensation expense         $ 5,000   $ 5,000 $ 2,800   $ 1,600  
2013 Plan | Trustee Awards, Restricted Stock Units (RSUs)                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Granted (in shares)             32,831 36,784 40,957    
Grant date value (in dollars per share)             $ 19.80 $ 17.67 $ 15.87    
2013 Plan | Performance based restricted stock units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Percentage of shares awarded         30.00%     20.00% 20.00%    
Grant date value (in dollars per share)         $ 29.34     $ 26.33 $ 19.22    
Grant date fair value (in dollars per share)         $ 19.80     $ 17.67 $ 15.87    
Officer | 2013 Plan | Restricted Share Units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Granted (in shares)   174,320 104,553                
Vesting period             3 years        
Officer | 2013 Plan | Market Based RSU                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Percentage of shares awarded             70.00% 80.00% 80.00%    
Grant date value (in dollars per share)             $ 33.43 $ 28.50 $ 20.06    
Trustees | 2013 Plan | Restricted Share Units                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Vesting period             2 years        
Number of dividend equivalent included in award   1                  
Trustees | 2013 Plan | Trustee Awards, Restricted Stock Units (RSUs)                      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]                      
Granted (in shares)   32,831 36,784 40,957